UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

Chemical modification of bark tannins for adhesive formulation Laks, Peter E. 1984

Your browser doesn't seem to have a PDF viewer, please download the PDF to view this item.

Item Metadata

Download

Media
831-UBC_1984_A1 L34.pdf [ 7.35MB ]
Metadata
JSON: 831-1.0096577.json
JSON-LD: 831-1.0096577-ld.json
RDF/XML (Pretty): 831-1.0096577-rdf.xml
RDF/JSON: 831-1.0096577-rdf.json
Turtle: 831-1.0096577-turtle.txt
N-Triples: 831-1.0096577-rdf-ntriples.txt
Original Record: 831-1.0096577-source.json
Full Text
831-1.0096577-fulltext.txt
Citation
831-1.0096577.ris

Full Text

Chemical Modification of Bark Tannins for Adhesive Formulation by Peter Edward Laks B.Sc., Simon Fraser University, 1976 M.Sc, Simon Fraser University, 1980 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in THE FACULTY OF GRADUATE STUDIES (Department of Forestry) We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA March, 1984 © Peter E. Laks, 1984 In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f t h e r e q u i r e m e n t s f o r an a d v a n c e d d e g r e e a t t h e U n i v e r s i t y o f B r i t i s h C o l u m b i a , I a g r e e t h a t t h e L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and s t u d y . I f u r t h e r a g r e e t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y p u r p o s e s may be g r a n t e d by t h e Head of my D e partment o r by h i s o r h e r r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t c o p y i n g o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . D e partment of F o r e s t r y The U n i v e r s i t y of B r i t i s h C o l u m b i a 2075 Wesbrook P l a c e V a n c o u v e r , Canada V6T 1W5 D a t e : 29 March 1984 i i ABSTRACT A r e a c t i o n i s d e s c r i b e d t h a t c l e a v e s c a t e c h i n ( I ) o r c o n i f e r t a n n i n s ( I I ) i n t o c a t e c h o l ( I I I ) and q u i n o l i n e d e r i v a t i v e s ( I V and V ) . The r e a g e n t and c o n d i t i o n s r e q u i r e d f o r t h i s r e a c t i o n were 30% ammonium s u l p h i t e i n c o n c e n t r a t e d ammonium h y d r o x i d e s o l u t i o n h e a t e d t o 175° C f o r 1 t o 3 h o u r s . The o p t i m i z a t i o n o f t h e s e c o n d i t i o n s i s d e s c r i b e d a l o n g w i t h a q u i c k g a s c h r o m a t o g r a p h y - b a s e d a s s a y p r o c e d u r e f o r c a t e c h o l . A m e c h a n i s m f o r t h e r e a c t i o n o f c a t e c h i n u n d e r t h e s e r e a c t i o n c o n d i t i o n s i s p r o p o s e d b a s e d on t h e s t r u c t u r e o f t h e end p r o d u c t s , a n d t h e b e h a v i o r o f compounds r e l a t e d t o t h e s t a r t i n g m a t e r i a l . I t was f o u n d t h a t an u n d e r s t a n d i n g o f t h e c l a s s i c B u c h e r e r r e a c t i o n was n e c e s s a r y f o r e l u c i d a t i o n o f t h e c l e a v a g e r e a c t i o n , so a d i s c u s s i o n o f t h e f o r m e r i s p r e s e n t e d . The p r o d u c t i o n o f c a t e c h o l a n d o t h e r s i m p l e p h e n o l i c s f r o m t r e e b a r k t a n n i n s c o u l d be i m p o r t a n t i n t h e u t i l i z a t i o n o f t h e l a t t e r m a t e r i a l s as a d h e s i v e s i n t h e f o r e s t p r o d u c t i n d u s t r y . A r e v i e w o f t h e l i t e r a t u r e on t a n n i n - b a s e d a d h e s i v e s i s p r e s e n t e d . A d h e s i v e f o r m u l a t i o n s b a s e d on t h e m i x t u r e o f o r g a n i c compounds p r o d u c e d f r o m t h e c l e a v a g e o f w e s t e r n h e m l o c k ( T s u g a  h e t e r o p h y l l a ( R a f . ) S a r g . ) b a r k t a n n i n s were q u a l i t a t i v e l y and q u a n t i t a t i v e l y e v a l u a t e d f o r s t r e n g t h - A l t h o u g h e a r l y i n d i c a t i o n s were p r o m i s i n g , t h e q u a l i t y o f t h e b a r k u s e d , a n d i i i i t s a b i l i t y to produce catechol, degraded rapidly during storage. Adhesives made with bark stored for more than two months did not produce good bond strengths. iv TABLE OF CONTENTS ABSTRACT . i i TABLE OF CONTENTS iv LIST OF TABLES ix LIST OF FIGURES . . . xi ABBREVIATIONS xv INTRODUCTION 1 CHAPTER I. LITERATURE REVIEW 4 I-A. The Nature of Western Hemlock Bark 4 ( 1 ) Anatomy '. 4 (2) Chemical Composition 8 I-B. Resins Made with Phenols and Formaldehyde 19 I-C. Western Hemlock Bark as a Source of Chemicals .... 25 (1) Adhesive Applications 25 (2) Non-Adhesive Applications 30 I-D.. Bark Polyflavanoids of Other Species; Chemistry and U t i l i z a t i o n in Adhesives 35 (1 ) Wattle 38 (2) Southern Pines 41 (3) Radiata Pine 43 I-E. Summary 45 CHAPTER II. THE TIME-TEMPERATURE DEPENDENCE OF THE YIELD V OF CATECHOL FROM CATECHIN AND WESTERN HEMLOCK BARK POLYPHENOLS 47 (1) GC Assay Using Acetylated Catechol 48 (2) Assay System for Underivatized Catechol 52 (3) Optimization of Catechol Yie l d from Catechin .... 56 (4) Optimization of Catechol Yield from Bark Extract 59 (5) Catechol Yield from Sequential Bark Extracts .... 61 (6) Summary 65 CHAPTER II I . INVESTIGATION OF THE REACTION BETWEEN CATECHIN AND (NH u) 2S0 3 IN CONCENTRATED NH„OH 66 III-A. I d e n t i f i c a t i o n of an Intermediate and Some Products 67 (1) 1 -(3,4-Dihydroxyphenyl)-2-hydroxy-3-(1,3,5-trihydroxyphenyl)propanesulphonic Acid 67 (2) 3-Amino-5-hydroxy-7-quinolinesulphonic Acid 69 (3) 3,5-Diamino-7-quinolinesulphonic Acid 77 III-B. The Reaction of Some Model Compounds with (NH„) 2S0 3 in Concentrated NH„OH 81 (1) The Bucherer Reaction on Resorcinol and Phloroglucinol 82 (2) Catechol 91 (3) Wattle Bark Extract 96 III-C. A Mechanism for the Cleavage of Catechin into Catechol and Quinoline Derivatives 97 (1) Amination on the Phloroglucinolic A-Ring 100 (2) Amination at C3 100 (3) Dehydrogenation at C3-C4 103 vi (4) Cleavage of the C2-C1' Bond 106 (5) Rearrangement of the Non-Aromatic Catechin Cleavage Product 113 (6) Cleavage of Dihydroquercetin , 114 (7) Cleavage of Western Hemlock Bark Tannin 119 111-D. Summary 120 CHAPTER IV. FORMULATION OF ADHESIVES AND BOND EVALUATION .122 (1) Qualitative Adhesive Development 123 (2) Quantitative Adhesive Development 125 (3) Summary 128 CHAPTER V. SUMMARY 129 CHAPTER VI. EXPERIMENTAL 135 VI-A. General Information 135 (1) Spectroscopy and Chromatography .135 (2) General Methods 136 (3) Materials 1 37 VI-B. Chapter II 138 (1) Acetylated Catechol Assay Procedure .138 (2) Underivatized Catechol Assay Procedure 139 (3) Typical Procedure for Investigating the Time-Temperature-Yield Relationship of Catechol Produced from Catechin 140 (4) Catechol Yield of Products from the Extraction Procedure of Fraser and Swan 141 (5) Extraction with Neutral Solvents and Catechol Yiel d 142 (6) Preparation of Catechinic Acid and Reaction with v i i 30% (NHft) 2 S O 3 / N H 3 ..143 (7) Maximum Yield of Catechol from Western Hemlock Bark 145 VI-C. Chapter III 146 (1) Isolation of 1 -(3,4-Dihydroxyphenyl)-2-hydroxy-3-(1 ,3,5-trihydroxyphenyl)propanesulphonic Acid ....146 (2) The Reaction of 1 -(3,4-Dihydroxypheny1)-2-hydroxy-(1,3,5-trihydroxyphenyl)propanesulphonic Acid with (NH 4) 2S0 3 in Ammonia Solution at High Temperatures . .- 147 (3) Isolation of Catechol and 3-Amino-5-hydroxy-7-quinolinesulphonic Acid 147 (4) Acetylation of 3-Amino-5-hydroxy-7-quinolinesulphonic Acid 150 (5) Isolation of 3,5-Diamino-7-quinolinesulphonic Acid 151 (6) Reaction of Phloroglucinol with (NH„) 2SO 3/NH 3 ...152 (7) Reaction of Catechol with (NH„) 2S0 3/NH 3 153 (8) Reaction of Resorcinol with <NH4)2S03/NH3 153 (9) Reaction of Wattle Bark Extract with (NH 4) 2S0 3/NH 3 154 (10) Reaction of Dihydroquercetin with (NH t t) 2S0 3/NH 3 155 (11) Reaction of Protocatechuic Acid with (NH«) 2S0 3/NH 3 156 (12) The Formation of Catechol from Catechin in the Presence and Absence of 0 2 . .... 156 (13) I d e n t i f i c a t i o n of Products from the Reaction of v i i i Western Hemlock Bark Polyphenols with (NH f t) 2S0 3/NH 3 157 VI-D. Chapter IV 158 (1) Isolation of the Organic Products from the Reaction of Western Hemlock Bark with (NH„) 2S0 3/NH 3 for Adhesive Formulation 158 (2) General Method of Adhesive Formulation 160 (3) Qualitative Technique for Adhesive Bond Evaluation 161 (4) Quantitative Evaluation of Bond Strength 162 BIBLIOGRAPHY 164 APPENDIX. S t a t i s t i c a l Analysis of Quantitative Bond Evaluat ion 177 i x LIST OF TABLES 1-1. Some Average Data on the Physical Characteristics of the Bark of Three Important B.C. Conifers 7 1-2. Chemical Analysis of Western Hemlock Bark 9 1-3. Commercial Polyflavanoid Products 32 1-4. Molecular Weights and Dis t r i b u t i o n of Bark Polyphenols 38 1 1 1 — 1. Non-Hydrogen Containing Bond Lengths of AHQSA 79 III-2. Non-Hydrogen Containing Bond Angles of AHQSA 79 III-3. AHQSA Bond Lengths Involving Hydrogen Atoms 80 111-4. AHQSA Bond Angles Involving Hydrogen Atoms 80 III-5. Resonance Energies of Some Aromatic Compounds 86 III- 6. Concentration of the Enol Tautomers of Some Diketones in Aqueous Solution 93 111 — 7 . Examples of Some Common Electron-Donating, Middle and Leaving Groups Found in Compounds Undergoing Heterolytic Cleavage 112 IV- 1. Results of Shear Tests on a Three-Ply Panel 126 VI-1. Conditions and Yield of Products from the Extraction Procedure According to Fraser and Swan 142 VI-2. Major IR Absorbances of Products from the Extraction Procedure According to Fraser and Swan 143 VI-3. Conditions and Yields of Products from the Neutral X Solvent Extraction Series 144 VI-4. Major IR Absorbances of Products from the Neutral Solvent Extraction Series 145 x i L I S T O F F I G U R E S 1 - 1 . B a r k S t r u c t u r e 5 1 - 2 . F l a v a n o i d S k e l e t o n 10 1 - 3 . S t r u c t u r e s o f S o m e F l a v a n o i d s a n d R e l a t e d C o m p o u n d s I s o l a t e d f r o m W e s t e r n H e m l o c k B a r k 11 1 - 4 . P r o p o s e d P o l y c y a n i d i n S t r u c t u r e o f W e s t e r n H e m l o c k C o l o r i n g M a t t e r 12 1 - 5 . S t r u c t u r e s o f C y a n i d i n a n d P e l a r g o n i d i n • • • • 1 3 1 - 6 . T h i o g l y c o l y s i s P r o d u c t s o f W e s t e r n H e m l o c k T a n n i n . . . 14 1 - 7 . S t r u c t u r e o f W e s t e r n H e m l o c k B a r k T a n n i n 1 5 1 - 8 . P o l y q u i n o n e - M e t h i d e S t r u c t u r e f o r t h e P h l o b a p h e n e s S u g g e s t e d b y H e r r i c k a n d H e r g e r t 17 1 - 9 . B a s e I n d u c e d R e a r r a n g e m e n t o f C a t e c h i n t o C a t e c h i n i c A c i d 18 1 - 1 0 . R e l a t i v e R e a c t i v i t y o f F o r m a l d e h y d e w i t h S o m e P h e n o l s 2 0 1 - 1 1 . S e l f C o n d e n s a t i o n o f F o r m a l d e h y d e 21 1 - 1 2 . D e c o m p o s i t i o n o f H e x a m i n e i n A l k a l i n e S o l u t i o n 2 2 1 - 1 3 . I m p o r t a n t R e a c t i o n s i n P h e n o l - F o r m a l d e h y d e R e s i n F o r m u l a t i o n 2 3 1 - 1 4 . Q u i n o n e M e t h i d e s a s I n t e r m e d i a t e s i n t h e F o r m a t i o n o f a P h e n o l - F o r m a l d e h y d e R e s i n 2 4 1 - 1 5 . S t r u c t u r e o f T r i m e t h y l o l p h e n o l . . . 2 6 x i i 1-16. Prices of Benzene, Phenol and PF Resin from 1963 to 1975 28 1-17. Sulphonation of Catechin 33 1-18. Substitution Patterns in Basic Units of Bark Polyflavanoids 37 1 - 1 9 . Catechin - Resorcinol Adduct 42 I- 20. The Structure of 4,4'-Diphenylmethane Diisocyanate 44 11 — 1. Typical Gas Chromatogram of Acetylated Catechol and Phloroglucinol 50 II- 2. Calibration Graph for Acetylated Catechin 51 11-3. GC-Injection Systems 54 11-4. Calibration Graph for Underivatized Catechol 55 11-5. Typical Gas Chromatogram of Catechol and o-Cresol .. 57 II-6. Molar Yields of Catechol from Catechin at 125° C, 150° C, 175° C and 200° C for Various Reaction Times Using (NH„) 2S0 3 58 II-7. Molar Yields of Catechol from Catechin at 100° C and 175° C for Various Reaction Times Using (NH a) 2S0 3 59 II-8. Weight Percent Yields of Catechin from Western Hemlock Bark-Ethanol Extract at 150° C, 175° C and 200° C for Various Reaction Times Using (NH«) 2S0 3/NH 3 .. 60 11-9. Yield of Extracts and Catechol from Four Sequential Extractions of Western Hemlock Bark 62 11-10. Yie l d of Extracts and Catechol from Six Sequential Extractions of Western Hemlock Bark 63 111 — 1 . The Reaction of Catechin with Sodium Bisulphite ... 68 111-2. Comparison of the NMR Spectra of Catechin and i t s S u l p h o n a t e d R e a c t i o n P r o d u c t 70 111-3. The NMR S p e c t r u m o f 3 - A m i n o - 5 - h y d r o x y - 7 -q u i n o l i n e s u l p h o n i c A c i d 72 111 -4. NMR S p e c t r a l D a t a o f Q u i n o l i n e 73 111 — 5. D i s s o c i a t i o n o f T e t r a m e t h y l a m m o n i u m S a l t s o f S u l p h o n i c A c i d s 75 111-6. T i t r a t i o n o f 3 - A m i n o - 5 - h y d r o x y - 7 - q u i n o l i n e s u l f o n i c A c i d 76 I I I - 7 . S t r u c t u r a l and T h r e e - D i m e n s i o n a l R e p r e s e n t a t i o n s o f 3 - A m i n o - 5 - h y d r o x y - 7 - q u i n o l i n e s u l f o n i c A c i d . . 78 111-8 . Ammonium S a l t a n d A c i d Forms o f 3 , 5 - D i a m i n o - 7 -q u i n o l i n e s u l p h o n a t e 81 111 — 9. The M e c h a n i s m o f t h e B u c h e r e r R e a c t i o n A c c o r d i n g t o F u c h s 84 111 — 10. S t r u c t u r e o f t h e B i s u l p h i t e A d d i t i o n P r o d u c t s o f P h l o r o g l u c i n o l and R e s o r c i n o l 84 111 — 11 . The M e c h a n i s m o f t h e B u c h e r e r R e a c t i o n on N a p h t h o l s A c c o r d i n g t o S e e b o t h 85 1 1 1 - 12 . The A d d i t i o n o f B i s u l p h i t e t o 2 - N a p h t h o l 88 111 — 13 . Two P o s s i b l e S u b s t i t u t i o n M e c h a n i s m s 90 111 — 14 . The R e a c t i o n o f Ammonia and Amines w i t h C a r b o n y l Compounds 91 111 - 1 5 . K e t o - E n o l E q u i l i b r i a o f C a t e c h i n and R e s o r c i n o l .. 92 11 1 - 16. H y d r o g e n - B o n d i n g i n t h e M o n o - E n o l T a u t o m e r s o f A c y c l i c K e t o n e s 95 111 — 17. M a j o r P r o d u c t s f r o m t h e C l e a v a g e o f C a t e c h i n 98 111 — 18 . S t a n d a r d N u m b e r i n g S y s t e m f o r Q u i n o l i n e x i v D e r i v a t i v e s 99 111- 19. I n t r o d u c t i o n of t h e C5 and C9 Amino G r o u p s 101 111-20. A Mechanism f o r t h e A m i n a t i o n a t C3 102 111-21 . Examples of D i s p r o p o r t i o n a t i o n 105 111-22. T a u t o m e r i c Forms of C a t e c h o l and C a t e c h o l as a L e a v i n g - G r o u p 107 111-23. F o r m a t i o n of C a t e c h o l by ^ - E l i m i n a t i o n 107 111-24. S u l p h o n a t e d F i s e t i n i d o l 109 111-2 5. D i s p r o p o r t i o n a t i o n of t h e C a t e c h i n S u l p h o n a t i o n I n t e r m e d i a t e 110 111-26. F o r m a t i o n of C a t e c h o l and P h l o r o g l u c i n o l by an E x t e n d e d E l i m i n a t i o n from S u l p h i t e d , D e h y d r o g e n a t e d C a t e c h i n 111 111-27 . Rearrangement of t h e N o n - A r o m a t i c C l e a v a g e P r o d u c t t o a S u b s t i t u t e d Q u i n o l i n e 114 111-28. The F o r m a t i o n of 3 - P h e n o l s u l p h o n i c A c i d from R e s o r c i n o l 115 111-29. Key I n t e r m e d i a t e s i n t h e P r o p o s e d Mechanism f o r t h e C l e a v a g e of C a t e c h i n t o C a t e c h o l and 3-Amino-5-h y d r o x y - 7 - q u i n o l i n e s u l p h o n i c A c i d 116 111-30 . The E x p e c t e d R e a c t i o n Sequence of D i h y d r o q u e r c e t i n w i t h (NH a ) 2 SO 3 /NH 3 ....117 111 — 31 . A Mechanism f o r t h e P r o d u c t i o n of P h l o r o g l u c i n o l from D i h y d r o q u e r c e t i n 118 V-1. S h e a r - T e s t Samples 163 XV ABBREVIATIONS PF - P h e n o l - F o r m a l d e h y d e PRF - P h e n o l - R e s o r c i n o l - F o r m a l d e h y d e RF - R e s o r c i n o l - F o r m a l d e h y d e r . e . - r e s o n a n c e e n e r g y HMWF - H i g h M o l e c u l a r Weight F r a c t i o n LMWF - Low M o l e c u l a r Weight F r a c t i o n SS - Sh e a r S t r e n g t h WF - Wood F a i l u r e 1 INTRODUCTION We a r e l i v i n g i n a w o r l d w i t h a g r o w i n g dependance on man-made m a t e r i a l s . S y n t h e t i c p l a s t i c s a r e becoming i n c r e a s i n g l y i m p o r t a n t f o r c l o t h i n g , a u t o m o b i l e s , a d h e s i v e s f o r b u i l d i n g c o n s t r u c t i o n , e t c . , w h i l e t h e p r i m a r y s o u r c e of t h e s e p l a s t i c s , p e t r o l e u m , i s becoming i n c r e a s i n g l y s c a r c e . R e c e n t l y , t h e r e has been a r e b i r t h of i n t e r e s t i n p r o d u c i n g c h e m i c a l s from r e n e w a b l e r e s o u r c e s s u c h as a g r i c u l t u r a l and f o r e s t r e s i d u e s . The o i l c r i s i s o f 1973 was t h e p r i m a r y c a u s e of t h i s . Government r e s e a r c h - f u n d i n g a g e n c i e s have become aware t h a t p e t r o l e u m w i l l i n e v i t a b l y be more e x p e n s i v e t o p r o d u c e and be i n s h o r t e r s u p p l y as t h e w o r l d ' s e a s i l y a c c e s s i b l e o i l - f i e l d s d r y up. S u b s t i t u t e s f o r e n e r g y and c h e m i c a l p r o d u c t s d e r i v e d from p e t r o l e u m w i l l have t o be f o u n d . In Canada, f o r e s t i n d u s t r y b y - p r o d u c t s s u c h as l i g n i n d e r i v a t i v e s , f o l i a g e , and b a r k a r e o b v i o u s c a n d i d a t e s t o a t l e a s t p a r t i a l l y s u b s t i t u t e f o r p e t r o l e u m i n e n e r g y and c h e m i c a l f e e d s t o c k a p p l i c a t i o n s . These m a t e r i a l s can be o b t a i n e d i n l a r g e q u a n t i t i e s and a r e a r e n e w a b l e r e s o u r c e . F u e l a p p l i c a t i o n s a r e s t r a i g h t f o r w a r d compared t o c h e m i c a l a p p l i c a t i o n s o f f o r e s t b y - p r o d u c t s . T h e r e have been e l a b o r a t e schemes and p r o c e s s e s e n v i s a g e d f o r c o n v e r t i n g r e n e w a b l e o r g a n i c m a t e r i a l s i n t o u s e f u l p r o d u c t s or i n d u s t r i a l c h e m i c a l s , but v e r y few a p p l i c a t i o n s a r e a c t u a l l y i n p r a c t i c e t o d a y . Many f a c t o r s 2 c o n t r i b u t e t o t h i s s t a t e of a f f a i r s . Two i m p o r t a n t ones a r e t h e s t i l l r e l a t i v e l y low c o s t o f . p e t r o l e u m t h a t makes c o m p e t i t i v e p r o c e s s e s , b a s e d on r e n e w a b l e r e s o u r c e s , u n e c o n o m i c a l , and a f u n d a m e n t a l l a c k of knowledge a b o u t t h e c h e m i s t r y o f t h e complex o r g a n i c m o l e c u l e s t h a t make up t h e b i o m a s s r e s o u r c e . The work d e s c r i b e d h e r e i s c o n c e r n e d w i t h t h e use of ba r k from an i m p o r t a n t l o c a l s o f t w o o d , T s u q a h e t e r o p h y l l a ( R a f f . ) S a r g . ( w e s t e r n h e m l o c k ) , as a s o u r c e of c h e m i c a l s t h a t c o u l d s u b s t i t u t e f o r p e t r o l e u m - d e r i v e d p h e n o l and r e s o r c i n o l i n a d h e s i v e s u s e d i n t h e f o r e s t p r o d u c t s i n d u s t r y . W e s t e r n hemlock was c h o s e n b e c a u s e t h e b a r k c o n t a i n s l a r g e amounts of t a n n i n , a complex p h e n o l i c p o l y m e r . The c h e m i c a l s t r u c t u r e of t a n n i n s u g g e s t s t h a t i t c o u l d be used as a d i r e c t s u b s t i t u t e f o r p h e n o l o r r e s o r c i n o l i n p h e n o l i c a d h e s i v e s . T h i s a p p r o a c h has worked w i t h t h e t a n n i n from some s p e c i e s . However, f o r v a r i o u s r e a s o n s t h a t w i l l be d e s c r i b e d l a t e r , s o f t w o o d t a n n i n s ( i n c l u d i n g w e s t e r n hemlock) have been s u c c e s s f u l i n a d h e s i v e a p p l i c a t i o n s o n l y when t h e ba r k m a t e r i a l i s us e d as an e x t e n d e r , r a t h e r t h a n as a s u b s t i t u t e , f o r p h e n o l or r e s o r c i n o l i n t h e s e a d h e s i v e s . C h e m i c a l m o d i f i c a t i o n of t h e s o f t w o o d t a n n i n s a p p e a r s t o be n e c e s s a r y i n o r d e r t o use them w i t h o u t f o r t i f i c a t i o n w i t h c o n v e n t i o n a l r e s i n s . The u l t i m a t e o b j e c t i v e of t h e r e s e a r c h p r e s e n t e d i n t h i s t h e s i s was t o c h e m i c a l l y m o d i f y w e s t e r n hemlock b a r k e x t r a c t so i t can be used c o m m e r c i a l l y as an a d h e s i v e w i t h o u t h a v i n g t o add any s y n t h e t i c r e s i n as a f o r t i f i e r . T h i s was done by u s i n g a r e a c t i o n t h a t b r e a k s up w e s t e r n hemlock b a r k t a n n i n i n t o 3 c a t e c h o l and o t h e r p r o d u c t s . In t h e e l u c i d a t i o n of t h e mechanism of t h i s r e a c t i o n , much of t h e work was done w i t h c a t e c h i n , w h i c h has o f t e n been u s e d as a s i m p l e model compound of t h e complex t a n n i n s . A r e a c t i o n mechanism w i l l be p r o p o s e d b a s e d on t h e r e s u l t s of e x p e r i m e n t s u s i n g t h i s , and o t h e r compounds, as models. B e f o r e t h e m e c h a n i s t i c i n v e s t i g a t i o n s were done, t h e y i e l d of c a t e c h o l from c a t e c h i n and w e s t e r n hemlock b a r k t a n n i n s was o p t i m i z e d by i n v e s t i g a t i n g t h e r e l a t i o n s h i p s between c a t e c h o l y i e l d and r e a c t i o n t e m p e r a t u r e and t i m e . In t h i s way, t h e y i e l d of t h e c o - p r o d u c t s of c a t e c h o l from c a t e c h i n were a l s o m a x i m i z e d , a l l o w i n g e a s i e r i s o l a t i o n of t h e s e compounds i n r e a s o n a b l e q u a n t i t i e s and f a c i l i t a t i n g t h e i r i d e n t i f i c a t i o n . F i n a l l y , e x p e r i m e n t s were done t o e v a l u a t e t h e a d h e s i v e p r o p e r t i e s of t h e p r o d u c t m i x t u r e o b t a i n e d from w e s t e r n hemlock b a r k t a n n i n s u s i n g t h i s c l e a v a g e r e a c t i o n . 4 CHAPTER I . LITERATURE REVIEW I-A. The N a t u r e o f W e s t e r n Hemlock B a r k B e f o r e a c o m p l e x o r g a n i c m a t e r i a l l i k e w e s t e r n h e m l o c k b a r k c a n be u t i l i z e d e f f i c i e n t l y i n any a p p l i c a t i o n , an u n d e r s t a n d i n g o f i t s p h y s i c a l and c h e m i c a l n a t u r e must be d e v e l o p e d . T h i s i s t h e p u r p o s e o f t h i s s e c t i o n o f t h e l i t e r a t u r e r e v i e w . (1) Anatomy The m a t u r e b a r k o f a c o n i f e r o u s t r e e h a s two d i s t i n c t p a r t s . A d j a c e n t t o t h e v a s c u l a r cambium i s a l a y e r o f i n n e r l i v i n g b a r k o f t e n c a l l e d t h e f u n c t i o n a l p h l o e m . T h i s t i s s u e p e r f o r m s t h e p h y s i o l o g i c a l f u n c t i o n o f c a r r y i n g n u t r i e n t s a nd hormones f r o m t h e l e a v e s t o t h e g r o w i n g x y l e m o r i m m a t u r e wood c e l l s on t h e i n s i d e o f t h e v a s c u l a r cambium. The o u t e r l a y e r o f b a r k , o r r h y t i d o m e , i s composed o f d e a d p h l o e m c e l l s w h i c h have no c o n d u c t i o n f u n c t i o n , b u t w h i c h h e l p t o p r o t e c t t h e l i v i n g c e l l s o f t h e t r e e f r o m m e c h a n i c a l damage. A l s o i n c l u d e d i n t h e o u t e r b a r k i s a t l e a s t one l a y e r o f t i s s u e c a l l e d t h e p e r i d e r m ( 1 , 2 ) ( s e e F i g u r e 1-1) . A t r e e grows i n d i a m e t e r by t h e v a s c u l a r cambium d i v i d i n g p e r i c l i n a l l y , p r o d u c i n g c e l l s t o t h e i n s i d e w h i c h grow and d i f f e r e n t i a t e i n t o t h e v a r i o u s x y l e m c e l l s . As t h e d i a m e t e r of t h e x y l e m i n c r e a s e s , t h e cambium must grow i n c i r c u m f e r e n c e by 5 Xylem F i g u r e 1 - 1 . Bark S t r u c t u r e o c c a s i o n a l o b l i q u e a n t i c l i n a l c e l l d i v i s i o n . The r a t e s of p e r i c l i n a l and a n t i c l i n a l cambium c e l l d i v i s i o n a r e b a l a n c e d , so th e d i a m e t e r growth o f t h e xylem i s i n harmony w i t h t h e c i r c u m f e r e n t i a l growth o f t h e cambium. However, th e mature phloem w h i c h was o r i g i n a l l y formed by p e r i c l i n a l d i v i s i o n of t h e cambium t o t h e o u t s i d e , has no mechanism f o r c i r c u m f e r e n t i a l g r o w t h . As t h e stem grows, t h e o u t e r bark c r a c k s and s l o u g h s o f f . In o r d e r t o p r o t e c t t h e l i v e phloem and cambium from e x p o s u r e t h a t would l e a d t o b a c t e r i a l or f u n g a l i n f e c t i o n and d e s i c c a t i o n , t h e p e r i d e r m forms w i t h i n t h e l i v i n g b a r k . 6 The p e r i d e r m i s composed o f t h r e e l a y e r s . The f i r s t t i s s u e t o form i s t h e p h e l l o g e n ( c o r k cambium), w h i c h i s a s i n g l e l a y e r of c e l l s o r i g i n a t i n g from phloem parenchyma c e l l s . In a s i m i l a r manner t o t h e v a s c u l a r cambium, t h e p h e l l o g e n c e l l s d i v i d e p e r i c l i n a l l y t o form a t h i n l a y e r of p h e l l o d e r m t o t h e i n s i d e ( u s u a l l y ) and a t h i c k e r l a y e r of p h e l l e m t o t h e o u t s i d e ( a l w a y s ) . The p h e l l e m or c o r k c e l l s have no p i t s i n t h e i r c e l l w a l l s and have a h i g h wax c o n t e n t . I t i s t h e c o r k w h i c h i s t h e i m p o r t a n t b a r r i e r p r o t e c t i n g t h e l i v e phloem, cambium and xylem c e l l s . When a p e r i d e r m f o r m s , t h e phloem c e l l s t o t h e o u t s i d e d i e and become p a r t of t h e o u t e r b a r k or r h y t i d o m e . S e v e r a l p e r i d e r m s may be c o n t a i n e d i n t h e r h y t i d o m e . W e s t e r n hemlock bark has a l l t h e f e a t u r e s d e s c r i b e d a b o v e . T a b l e 1-1 c o n t a i n s d a t a on some i m p o r t a n t p h y s i c a l c h a r a c t e r i s t i c s of w e s t e r n hemlock b a r k ( 3 ) . D a t a from two o t h e r s p e c i e s a r e g i v e n f o r c o m p a r a t i v e p u r p o s e s . F o r t h e r e l a t i v e l y s m a l l w e s t e r n hemlock t r e e s examined, th e a u t h o r s f o u n d an a v e r a g e t o t a l b a r k t h i c k n e s s e s of 0.252 i n c h e s . L a r g e r t r e e s have b a r k t h i c k n e s s e s o f up t o about 1 i n c h .(4). O t h e r i n f o r m a t i o n on p h y s i c a l p r o p e r t i e s of hemlock bark has been p u b l i s h e d ( 5 , 6 ) . In g e n e r a l , t h e r h y t i d o m e of w e s t e r n hemlock i s a d a r k r e d d i s h - b r o w n c o l o u r w i t h s c a l e s formed from s u c c e s s i v e p e r i d e r m s two t o t h r e e m i l l i m e t e r s i n t h i c k n e s s . The c o r k l a y e r i s q u i t e t h i n , a b o u t 20 c e l l s i n r a d i a l t h i c k n e s s . The i n n e r b a r k i s a l i g h t y e l l o w c o l o u r when f r e s h , but r a p i d l y o x i d i z e s t o r e d a f t e r e x p o s u r e ( 4 ) . Phloem anatomy i s i m p o r t a n t i n c h e m i c a l a p p l i c a t i o n s , B a r k T h i c k n e s s ( i n . ) M o i s t u r e C o n t e n t S p e c i f i c G r a v i t y (O.D. W g t . / G r e e n V o l . ) (%0 D. ) S p e c i e s D . B . H . ( i n . ) H e i g h t ( f t . ) I n n e r O u t e r I n n e r O u t e r I n n e r O u t e r D o u g l a s F i r 15 66 0. 237 0. 393 133 80. 3 0.451 0.427 W.Hem)ock 10 49 0. 126 0.116 134 6 5 . 2 0. 449 0. 564 S i 1 v e r f i r 8 47 0. 129 0.071 77 . 4 39 . 6 0.525 0.581 ( A v e r a g e o f d a t a f r o m s a m p l e s t a k e n a t 1 a n d 4.5 f o o t h e i g h t s ) T a b l e 1-1. Some A v e r a g e D a t a o f t h e P h y s i c a l C h a r a c t i s t i c s o f t h e B a r k o f T h r e e I m p o r t a n t B.C. C o n i f e r s ( 3 ) 8 b e c a u s e i t has an i n f l u e n c e on t h e c h e m i c a l c o m p o s i t i o n of t h e b a r k . F o r example, D o u g l a s f i r ( P s e u d o t s u g a m e n z i e s i i ( M i r b . ) F r a n c o . ) has v e r y t h i c k p h e l l e m l a y e r s . A s s o c i a t e d w i t h t h e c o r k , a r e c o r r e s p o n d i n g l y l a r g e amounts of waxes t h a t have been c o m m e r c i a l l y e x t r a c t e d from t h i s s p e c i e s ( 7 ) . F o r w e s t e r n hemlock, t h e a v e r a g e m o l e c u l a r w e i g h t of t h e b a r k t a n n i n s c o u l d be d i f f e r e n t i n t h e i n n e r and o u t e r b a r k z o n e s . The r e l a t i v e p r o p o r t i o n s of the two zones i n a g i v e n sample of b a r k may a f f e c t t h e s u i t a b i l i t y of t h e e x t r a c t e d p o l y p h e n o l i c s f o r c h e m i c a l a p p l i c a t i o n s . (2) C h e m i c a l C o m p o s i t i o n The s u b s t a n c e s t h a t make up hemlock b a r k a r e a complex m i x t u r e . C e l l u l o s e , h e m i c e l l u l o s e and l i g n i n , t h e i m p o r t a n t c o n s t i t u e n t s of wood, a r e a l s o f o u n d i n b a r k , but w h i l e t h e y a c c o u n t f o r a b o u t 95% of t h e woody m a t e r i a l , i n b a r k t h e y make up o n l y a b o u t 50%. The r e s t of t h e bark m a t e r i a l i s p r i m a r i l y p o l y f l a v a n o i d s . T a b l e 1-2 shows the c h e m i c a l a n a l y s i s o f a i r -d r i e d , f r e s h hemlock bark as r e p o r t e d by H e r r i c k ( 8 ) . T h e r e has been l i t t l e work done s p e c i f i c a l l y on t h e c h a r a c t e r i s t i c s of l i g n i n and c e l l u l o s e from w e s t e r n hemlock b a r k . R e s e a r c h on o t h e r c o n i f e r s p e c i e s i n d i c a t e s t h a t t h e d i f f e r e n c e s between c o n i f e r bark c e l l u l o s e and l i g n i n , and t h o s e m a t e r i a l s f o u n d i n wood a r e r e l a t i v e l y minor ( 1 0 , 1 1 , 1 2 , 1 3 ) . F o r example, h o l o c e l l u l o s e i s o l a t e d from bark o f t e n c o n t a i n s a 9 F r a c t i o n % By Weight C e l l u l o s e 20.5 H e m i c e l l u l o s e 16.2 L i g n i n 15.2 Ash 0.3 P h e n o l i c A c i d s 18.5 E x t r a c t i v e s 29.3 Wax 2.8 F l a v a n o i d s & C o l o r i n g M a t t e r 3.6 T a n n i n ( w a t e r s o l u b l e ) 12.7 P h l o b a p h e n e s 5.3 C a r b o h y d r a t e s ( w a t e r s o l u b l e ) 4.9 T a b l e 1-2. C h e m i c a l A n a l y s i s o f W e s t e r n Hemlock Bark (8) s i g n i f i c a n t l y h i g h e r p r o p o r t i o n o f mannose ( 1 2 , 1 4 ) , and some s t u d i e s i n d i c a t e t h e l i g n i n of c o n i f e r b a r k s may be more h i g h l y c r o s s l i n k e d t h a n wood l i g n i n ( 1 5 , 1 6 ) . R e s e a r c h on t h e c h e m i c a l c o m p o s i t i o n o f w e s t e r n hemlock b a r k has f o c u s e d on t h e p o l y p h e n o l i c p o r t i o n s . In g e n e r a l , t h e s e compounds have a s t r u c t u r e b a s e d on t h e f l a v a n o i d c a r b o n s k e l e t o n . F i g u r e 1-2 shows t h e r i n g numbering s y s t e m and r i n g d e s i g n a t i o n s of t h e f l a v a n o i d s . In t h e p a s t , s o l u b i l i t y i n v a r i o u s s o l v e n t s was u s e d as t h e c l a s s i f i c a t i o n method f o r bark e x t r a c t i o n s . S i m p l e f l a v a n o i d s were s o l u b l e i n d i e t h y l e t h e r , t a n n i n s were t h e p o l y p h e n o l p o r t i o n t h a t d i s s o l v e d i n water and a l c o h o l , p h l o b a p h e n e s were s o l u b l e i n e t h a n o l but i n s o l u b l e i n w a t e r , and t h e p h e n o l i c a c i d s were e x t r a c t a b l e w i t h d i l u t e a l k a l i but i n s o l u b l e i n n e u t r a l s o l v e n t s . I t i s a p p a r e n t now, t h a t t h e l a s t t h r e e compound g r o u p s a r e v e r y c l o s e l y r e l a t e d and p r o b a b l y d i f f e r o n l y i n d e g r e e of p o l y m e r i z a t i o n or l e v e l of o x i d a t i o n i n t h e c a s e of t h e p h l o b a p h e n e s . 10 F i g u r e 1-2. F l a v a n o i d S k e l e t o n The s t r u c t u r e s o f some s i m p l e f l a v a n o i d s and r e l a t e d compounds t h a t have been i s o l a t e d f r o m w e s t e r n hemlock b a r k a r e shown i n F i g u r e 1-3. The e t h e r s o l u b l e , r e d - p u r p l e c o l o r i n g m a t t e r a s s o c i a t e d w i t h t h e f l a v a n o i d s h as n o t been w e l l c h a r a c t e r i z e d . A l k a l i f u s i o n o f t h i s m a t e r i a l i n a e u t e c t . i c m i x t u r e o f p o t a s s i u m and s o d i u m h y d r o x i d e g i v e s p r o t o c a t e c h u i c a c i d , c a t e c h o l and p h l o r o g l u c i n o l ( 1 7 ) , t h e same p r o d u c t s o b t a i n e d by f u s i o n o f t a n n i n . H e r g e r t h a s s u g g e s t e d t h a t t h e m a t e r i a l i s p r o b a b l y a p o l y m e r o f c y a n i d i n ( F i g u r e 1 - 4 ) . H i s c o n c l u s i o n s were b a s e d on t h e UV a n d IR s p e c t r a o f t h i s m a t e r i a l a n d i t s b e h a v i o r i n c h r o m a t o g r a p h i c s y s t e m s ( 9 , 1 9 ) . S t r u c t u r a l e l u c i d a t i o n o f t h e m a j o r p o l y f l a v a n o i d c o m p o n e n t s h a s been done u s i n g some s p e c i a l i z e d t e c h n i q u e s . A l k a l i f u s i o n , m e n t i o n e d e a r l i e r , p r o v i d e s i n f o r m a t i o n on t h e h y d r o x y l a t i o n p a t t e r n s o f t h e A- a n d B - r i n g s f o u n d i n t h e monomer m o i e t i e s t h a t make up t h e f l a v a n o i d p o l y m e r ( 1 8 ) . A n a l y s i s o f a n t h o c y a n i d i n s , w h i c h a r e f o r m e d by d e g r a d a t i o n o f t h e p o l y f l a v a n o i d w i t h m i n e r a l a c i d s i n b o i l i n g a l c o h o l 11 O H 0 H Catechin C O O H C O O H O H H O Protocatechuic Acid O H O H O C H , H O Vanillic Acid O H Quercetin C O O H C O O H H O O C H , O H Catechol H O p- Hydroxy Benzoic Acid H O Ferulic Acid H O Phloroglucinol F i g u r e 1-3. S t r u c t u r e of Some F l a v a n o i d s and R e l a t e d Compounds I s o l a t e d from W e s t e r n Hemlock Bark (9,17) 1 2 F i g u r e 1-4. P r o p o s e d P o l y c y a n i d i n S t r u c t u r e of W e s t e rn Hemlock C o l o r i n g M a t t e r (19) s o l u t i o n , can g i v e i n f o r m a t i o n on t h e n a t u r e of t h e monomer, as can t h i o g l y c o l y s i s ( 2 0 ) . B o t h t h e s e t e c h n i q u e s c l e a v e i n t e r f l a v a n o i d bonds and g i v e p r o d u c t s t h a t have s t r u c t u r e s r e l a t e d t o t h e monomeric u n i t s of t h e p o l y f l a v a n o i d b e i n g d e g r a d e d . As m e n t i o n e d above, a l k a l i f u s i o n of w e s t e r n hemlock t a n n i n y i e l d e d m a i n l y p h l o r o g l u c i n o l , c a t e c h o l and p r o t o c a t e c h u i c a c i d , as' w e l l as s m a l l amounts of p a r a -h y d r o x y b e n z o i c a c i d ( 1 7 ) . D e g r a d a t i o n w i t h h y d r o c h l o r i c a c i d i n b o i l i n g i s o p r o p a n o l gave c y a n i d i n as t h e main p r o d u c t , a l o n g w i t h s m a l l amounts of a s e c o n d compound t e n t a t i v e l y i d e n t i f i e d as p e l a r g o n i d i n (9) ( F i g u r e 1 - 5 ) . The d e g r a d a t i o n of hemlock • t a n n i n by HSCH 2COOH ( t h i o g l y c o l y s i s ) was s t u d i e d by S e a r s and C a s e b i e r ( 2 1 ) . M e t h y l a t e d t a n n i n was d e g r a d e d by 60% t h i o g l y c o l i c a c i d a t 140° C t o g i v e two main p r o d u c t s i n a p p r o x i m a t e l y e q u a l q u a n t i t i e s (10% t o t a l y i e l d ) a f t e r f u r t h e r m e t h y l a t i o n . These were i d e n t i f i e d as b e i n g 2 . 3 - c i s and 2,3-t r a n s m e t h y l ( 3 ~ h y d r o x y - 5 , 7 , 3 ' , 4 ' - t e t r a m e t h o x y f l a v a n - 4 - y l - t h i o ) 1 3 F i g u r e 1-5. S t r u c t u r e s o f C y a n i d i n and P e l a r g o n i d i n a c e t a t e s ( F i g u r e 1-6). T h i s i n f o r m a t i o n i n d i c a t e s t h a t b o t h c a t e c h i n and e p i c a t e c h i n m o i e t i e s a r e p r e s e n t i n t h e t a n n i n p o l y m e r . E v i d e n c e f o r t h i s monomer m i x t u r e was r e p o r t e d e a r l i e r by H e r g e r t ( 1 7 ) , who f o u n d t h a t m i l d a c i d h y d r o l y s i s o f hemlock t a n n i n gave t r a c e s of c a t e c h i n and e p i c a t e c h i n . The t y p e of s t r u c t u r e f o r hemlock t a n n i n s u g g e s t e d by t h i s work, i s a polymer of c a t e c h i n and e p i c a t e c h i n m o i e t i e s j o i n e d by C ( 4 ) - C ( 8 ) i n t e r f l a v a n o i d bonds as shown i n F i g u r e 1-7. M o l e c u l a r w e i g h t s t u d i e s on a c e t y l a t e d t a n n i n i n d i c a t e d t h a t t h e number a v e r a g e m o l e c u l a r w e i g h t i s 1500-2000 (4-5 f l a v a n o i d u n i t s p e r t a n n i n m o l e c u l e ) ( 1 7 ) . However, t h i s r e p r e s e n t a t i o n may be somewhat s i m p l i s t i c . Hemingway (20) has 1 4 O C H 3 OCH 3 F i g u r e 1-6. T h i o g l y c o l y s i s P r o d u c t s of W e s t e r n Hemlock T a n n i n p o i n t e d o u t t h a t t h i o g l y c o l y s i s y i e l d s from p o l y f l a v a n o i d s c o n t a i n i n g o n l y C ( 4 ) - C ( 8 ) bonds s h o u l d be a l m o s t q u a n t i t a t i v e ( 2 2 ) . S i n c e hemlock t a n n i n t h i o g l y c o l y s i s has a much l o w e r y i e l d , t h e m o l e c u l e may w e l l c o n t a i n s t r u c t u r a l f e a t u r e s not y e t d e f i n e d . R e c e n t work has s u g g e s t e d t h a t t h e r e may be two t y p e s of t a n n i n s i n p l a n t s ; l i n e a r f l a v a n o i d p o l y m e r s w i t h m a i n l y C ( 4 ) -C(8) i n t e r f l a v a n o i d bonds and more g l o b u l a r , p o s s i b l y b r a n c h e d , p o l y f l a v a n o i d s where a l a r g e p r o p o r t i o n of t h e i n t e r f l a v a n o i d bonds a r e C ( 4 ) - C ( 6 ) . Haslam and h i s g r o u p (22) have f o u n d t h a t t h e d i m e r i c p r o c y a n i d i n s from S a l i x c a p r e a L., C r a t a e g u s  monoqyna J a c q . and o t h e r s p e c i e s , had a r a t i o of C ( 4 ) - C ( 8 ) 1 5 O H F i g u r e 1-7. S t r u c t u r e of W e s t e r n Hemlock Bark T a n n i n i n t e r f l a v a n o i d bonds t o C ( 4 ) - C ( 6 ) bonds of 8 or 9 t o 1, w h i l e t h e h i g h e r m o l e c u l a r w e ight p o l y f l a v a n o i d s have a l m o s t e x c l u s i v e l y C ( 4 ) - C ( 8 ) bonds ( 2 3 , 2 4 ) . C o n f o r m a t i o n a l s t u d i e s have i n d i c a t e d t h a t p o l y m e r s of t h i s t y p e a r e l i n e a r , t h r e a d -l i k e , s t r u c t u r e s w i t h t h e c a t e c h o l B - r i n g s on t h e o u t s i d e of t h e m o l e c u l e t a k i n g a h e l i c a l a r r a n g e m e n t ( 2 2 , 2 4 ) . Hemingway e_t a l . ( 2 5 ) , w o r k i n g w i t h p o l y f l a v a n o i d s of s o u t h e r n p i n e s p e c i e s , have f o u n d t h a t t h e t a n n i n s from t h e s e s p e c i e s a p p e a r t o c o n t a i n a much h i g h e r p r o p o r t i o n of C ( 4 ) - C ( 6 ) bonds and i n t h e i r n a t i v e s t a t e p r o b a b l y have g l o b u l a r , b r a n c h e d s t r u c t u r e s . T h e i r c o n c l u s i o n s were b a s e d on t h e s t r u c t u r e of i s o l a t e d d i - and t r i m e r i c f l a v a n o i d s and p a r t i a l t h i o l y t i c 16 d e g r a d a t i o n of t a n n i n s ( 2 6 , 2 7 , 2 8 ) . The p r e s e n c e of b r a n c h p o i n t s i n p i n e t a n n i n s has not y e t been p r o v e n d i r e c t l y , a l t h o u g h t h i o l y t i c c l e a v a g e r a t e s have p r o v i d e d i n d i r e c t e v i d e n c e f o r b r a n c h i n g . D e t a i l e d work of t h i s k i n d has not been done w i t h w e s t e r n hemlock t a n n i n s , but t h e t h i o g l y c o l y s i s d a t a o u t l i n e d above do show s i m i l a r i t i e s t o t h e b e h a v i o r of p i n e t a n n i n s under t h e s e c o n d i t i o n s . I t i s l i k e l y t h a t t h e s t r u c t u r e shown i n F i g u r e 1-7 i s t o o s i m p l i s t i c . T h e r e i s p r o b a b l y a r e l a t i v e l y h i g h p r o p o r t i o n of C ( 4 ) - C ( 6 ) bonds t o t h e C ( 4 ) - C ( 8 ) bonds shown and p o s s i b l y some b r a n c h i n g t h r o u g h t h e s e p o s i t i o n s . A l k a l i f u s i o n of t h e p h l o b a p h e n e f r a c t i o n o f w e s t e r n hemlock bark gave e s s e n t i a l l y t h e same p r o d u c t s as d e g r a d a t i o n of t h e t a n n i n ( 1 7 ) , w h i l e t h i o g l y c o l y s i s d i d not y i e l d any r e c o g n i z a b l e t h i o e t h e r s ( 2 0 ) . T h i s e v i d e n c e s u g g e s t s t h a t t h e p h l o b a p h e n e s a r e s t r u c t u r a l l y s i m i l a r t o t a n n i n but p r o b a b l y have t h e C - r i n g i n a h i g h e r o x i d a t i o n s t a t e ( 2 9 ) . The p h l o b a p h e n e s c o u l d be a h i g h e r m o l e c u l a r w e i g h t f r a c t i o n of t h e p o l y c y a n i d i n s e x t r a c t a b l e by e t h e r , as d e s c r i b e d above, o r a p o l y q u i n o n e s t r u c t u r e as s u g g e s t e d by H e r r i c k and H e r g e r t (30) ( F i g u r e 1-8). The p h e n o l i c a c i d s were o r i g i n a l l y named b e c a u s e o f t h e p r e s e n c e of p h e n o l i c g r o u p s and a c a r b o n y l f u n c t i o n a l i t y t h a t was assumed t o be due t o a c a r b o x y l i c a c i d ( 2 9 ) . The c a r b o n y l f u n c t i o n a l i t y c o u l d a l s o be i n d u c e d i n water s o l u b l e t a n n i n s by t r e a t m e n t w i t h base ( 3 1 ) . The p r o p e r t i e s of t h e a l k a l i s o l u b l e f r a c t i o n a r e d e f i n i t e l y m o d i f i e d by the e x t r a c t i o n p r o c e s s . A f t e r i s o l a t i o n , most or a l l of t h e p h e n o l i c a c i d m a t e r i a l i s 1 7 H O F i g u r e 1-8. P o l y q u i n o n e M e t h i d e S t r u c t u r e f o r t h e P h l o b a p h e n e s S u g g e s t e d by H e r r i c k and H e r g e r t ( 3 0 ) . s o l u b l e i n e t h a n o l ( 2 9 , 3 2 ) . T h i o g l y c o l y s i s o f h e m l o c k b a r k e x t r a c t e d w i t h n e u t r a l s o l v e n t s y i e l d s t h e same p r o d u c t s a s t h i o g l y c o l y s i s o f t a n n i n , b u t w i t h a h i g h e r p r o p o r t i o n o f t h e e p i c a t e c h i n d e r i v a t i v e ( 2 1 ) . T h i s i n f o r m a t i o n l e a d s t o t h e c o n c l u s i o n t h a t , b e f o r e e x t r a c t i o n , t h e p h e n o l i c a c i d f r a c t i o n has e s s e n t i a l l y t h e same s t r u c t u r e as t a n n i n b u t i s n o t s o l u b l e i n n e u t r a l s o l v e n t s due t o a h i g h e r m o l e c u l a r w e i g h t o r p e r h a p s more e x t e n s i v e c r o s s l i n k i n g ( 1 7 ) . Some i n s i g h t i n t o t h e a l k a l i i n d u c e d r e a r r a n g e m e n t o f t a n n i n was p r o v i d e d by t h e work o f S e a r s et. a l . (33) u s i n g c a t e c h i n as a model compound. I t was f o u n d t h a t c a t e c h i n u n d e r g o e s a r e a r r a n g e m e n t r e a c t i o n i n r e f l u x i n g d i l u t e s o d i u m h y d r o x i d e t o g i v e a compound c o n t a i n i n g an a c i d i c e n o l f u n c t i o n a l i t y ( c a t e c h i n i c a c i d , F i g u r e 1 - 9 ) . P r e s u m a b l y , a s i m i l a r a r r a n g e m e n t o c c u r s i n t h e h i g h m o l e c u l a r w e i g h t t a n n i n f r a c t i o n d u r i n g a l k a l i e x t r a c t i o n . I n summary, t h e f l a v a n o i d s f o u n d i n w e s t e r n hemlock b a r k 18 a r e b a s e d on t h e s t a n d a r d f l a v a n o i d c a r b o n s k e t e t o n . They range i n s i z e from t h e s i m p l e monomeric c o n s t i t u e n t s s u c h as c a t e c h i n t o t h e l a r g e r p o l y m e r s of u n d e t e r m i n e d s i z e c o n t a i n e d i n t h e p h e n o l i c a c i d f r a c t i o n . Bark p o l y p h e n o l s can be d i v i d e d i n t o two b a s i c t y p e s d e p e n d i n g on t h e o x i d a t i o n s t a t e o f t h e C - r i n g i n t h e monomeric u n i t . The p h l o b a p h e n e s and " c o l o r i n g m a t t e r " a r e more h i g h l y o x i d i z e d and p r e s e n t i n s m a l l e r q u a n t i t i e s t h a n t h e l e s s o x i d i z e d t a n n i n s and p h e n o l i c a c i d s . A l t h o u g h d a t a on t h e i n t e r f l a v a n o i d b o n d i n g i n w e s t e r n hemlock p o l y f l a v a n o i d s a r e l i m i t e d , some i n f e r e n c e s c a n be drawn from work done w i t h bark 1 9 e x t r a c t s of o t h e r c o n i f e r s p e c i e s . I n s t e a d of a r e g u l a r p olymer c o n t a i n i n g e x c l u s i v e l y C ( 4 ) - C ( 8 ) i n t e r f l a v a n o i d bonds, t h e r e i s now i n d i r e c t e v i d e n c e f o r t h e p r e s e n c e of b r a n c h i n g from t h e 6 p o s i t i o n of t h e c a t e c h i n and e p i c a t e c h i n m o i e t i e s . T h i s t y p e of s t r u c t u r e would g i v e t h e s e p o l y f l a v a n o i d s a g l o b u l a r c o n f o r m a t i o n i n s o l u t i o n . I-B. R e s i n s Made w i t h P h e n o l s and F o r m a l d e h y d e P h e n o l s c an r e a c t w i t h f o r m a l d e h y d e under a c i d i c or b a s i c c o n d i t i o n s t o form r i g i d c r o s s - l i n k e d p o l y m e r s t h a t have a v a r i e t y of a p p l i c a t i o n s d e p e n d i n g on t h e raw m a t e r i a l s u s e d , r e a c t i o n c o n d i t i o n s and t h e p a r t i c u l a r m a n u f a c t u r i n g p r o c e s s . One i m p o r t a n t use i s i n t h e f o r m u l a t i o n of p h e n o l - f o r m a l d e h y d e (PF) t h e r m o s e t t i n g r e s i n s or p h e n o l - r e s o r c i n o l - f o r m a l d e h y d e (PRF) c o l d - s e t t i n g r e s i n s u s e d i n t h e wood p r o d u c t s i n d u s t r y . In 1979, a p p r o x i m a t e l y 37% (8.26 X 10 8 kg) of t h e t h e r m o s e t t i n g r e s i n p r o d u c e d i n t h e U n i t e d S t a t e s ( i n c l u d i n g u r e a - f o r m a l d e h y d e t y p e s ) was used i n t h e m a n u f a c t u r e of f o r e s t p r o d u c t s ( 3 4 ) . Some c h e m i s t r y of t h e r e a c t i o n s between p h e n o l and f o r m a l d e h y d e under b a s i c c o n d i t i o n s i s p r e s e n t e d below. A c i d i c r e s i n s a r e not n o r m a l l y used f o r wood a p p l i c a t i o n s b e c a u s e o f p r o b l e m s w i t h d e g r a d a t i o n of t h e wood, and w i l l not be c o n s i d e r e d h e r e . C a t e c h o l and o t h e r p o l y h y d r o x y p h e n o l s w i l l r e a c t i n a s i m i l a r manner t o p h e n o l i t s e l f , but w i t h f a s t e r r e a c t i o n r a t e s . The r e l a t i v e r e a c t i v i t y of some r e l e v a n t 20 p h e n o l s w i t h f o r m a l d e h y d e i s g i v e n i n F i g u r e 1-10 OH OH HO> OH Monomer — Phenol Catechol OH OH Relative Reactivity — Resorcinol 2.5 3 HO^ ^OH Phloroglucinol 8 F i g u r e 1-10. R e l a t i v e R e a c t i v i t y of F o r m a l d e h y d e w i t h Some P h e n o l s (35) F r e e f o r m a l d e h y d e i s r a t h e r u n s t a b l e i n water s o l u t i o n , c o n d e n s i n g r e a d i l y i n t o complex e q u i l i b r i u m m i x t u r e s of p o l y m e r s p r i m a r i l y i n t h e h e m i f o r m a l form (36) ( F i g u r e 1-11). F o r m a l d e h y d e can be added t o a r e s i n i n forms o t h e r t h a n i n a water s o l u t i o n . P a r a f o r m a l d e h y d e , a s o l i d , i s a h i g h m o l e c u l a r w e i g h t h e m i f o r m a l p o l y m e r of f o r m a l d e h y d e . T h i s m a t e r i a l i s a v a i l a b l e i n v a r i o u s g r a d e s w i t h d i f f e r e n t a v e r a g e m o l e c u l a r w e i g h t s and p a r t i c l e s i z e s . P a r a f o r m a l d e h y d e decomposes f a i r l y r a p i d l y i n a l k a l i n e s o l u t i o n t o r e l e a s e f o r m a l d e h y d e . The d e p o l y m e r i z a t i o n p r o c e s s i s a c c e l e r a t e d by h e a t ( 3 6 ) . H e x a m e t h y l e n e t e t r a m i n e ( a l s o c a l l e d hexa or hexamine) i s most commonly us e d f o r t h e s e c o n d s t a g e of n o v o l a k p h e n o l -f o r m a l d e h y d e r e s i n c u r i n g , a f t e r t h e n o v a l a k has a l r e a d y been formed by r e a c t i o n of p h e n o l w i t h f o r m a l d e h y d e s o l u t i o n . 21 H n O + H 2 0 H O - ( - C H 2 - O ^ - H n H F i g u r e 1-11. S e l f C o n d e n s a t i o n of F o r m a l d e h y d e Hexamine can a l s o be us e d as a p r i m a r y f o r m a l d e h y d e s o u r c e under a l k a l i n e c o n d i t i o n s . I t s a d v a n t a g e i n b a s i c s o l u t i o n s i s t h a t i t decomposes t o f o r m a l d e h y d e o n l y a t h i g h t e m p e r a t u r e s ( a p p r o x i m a t e l y 150° C ) , a l l o w i n g a l o n g e r p o t - l i f e f o r a d h e s i v e s made w i t h t h i s f o r m a l d e h y d e s o u r c e ( 3 7 ) . The d e c o m p o s i t i o n of hexamine i n a l k a l i n e water s o l u t i o n i s shown i n F i g u r e 1-12. T h e r e have been c o n f l i c t i n g r e p o r t s on whether bonds made w i t h bark a d h e s i v e s c o n t a i n i n g hexamine, a r e more o r l e s s b o i l r e s i s t a n t t h a n a d h e s i v e s made w i t h f o r m a l i n or p a r a f o r m a l d e h y d e as t h e h a r d e n e r ( 3 9 , 4 0 ) . T h i s i s o b v i o u s l y an a r e a r e q u i r i n g more s t u d y . C o m m e r c i a l p h e n o l - f o r m a l d e h y d e r e s o l r e s i n s f o r wood a d h e s i v e a p p l i c a t i o n s a r e m a n u f a c t u r e d by m i x i n g p h e n o l w i t h a b a s i c c a t a l y s t i n a r e a c t i o n v e s s e l . Sodium h y d r o x i d e i s t h e most common base u s e d , a l t h o u g h b a r i u m h y d r o x i d e , c a l c i u m h y d r o x i d e , sodium c a r b o n a t e , and o r g a n i c amines can a l s o be employed, d e p e n d i n g on t h e s p e c i f i c a p p l i c a t i o n . Aqueous f o r m a l d e h y d e i s added t o g i v e a f o r m a l d e h y d e / p h e n o l m o l a r r a t i o of 1.8 t o 2.4. A f t e r i n i t i a l h e a t i n g , t h e t e m p e r a t u r e - i s c o n t r o l l e d t o a l l o w t h e c o n d e n s a t i o n r e a c t i o n t o p r o c e e d t o t h e 22 N(CH 3 ) 3 + 3 H2CO + 3 NH3 F i g u r e 1-12. D e c o m p o s i t i o n of Hexamine i n A l k a l i n e S o l u t i o n d e s i r e d e x t e n t . The r e s i n i s t h e n c o o l e d and and some water removed by e v a p o r a t i o n ( 4 1 ) . The i m p o r t a n t r e a c t i o n s t h a t o c c u r i n p h e n o l - f o r m a l d e h y d e r e s i n f o r m u l a t i o n a r e summarized i n F i g u r e 1-13. M e t h y l e n e and m e t h y l e n e e t h e r b r i d g e s between p h e n o l i c m o i e t i e s a r e p r o b a b l y b o t h p r e s e n t , as w e l l a s u n r e a c t e d m e t h y l o l g r o u p s ( 4 2 ) . A r e a c t i o n mechanism w i t h n e u t r a l q u i n o n e m e t h i d e i n t e r m e d i a t e s has a l s o been p r o p o s e d ( F i g u r e 1-14) ( 4 2 , 4 3 ) . To make an a d h e s i v e mix f o r wood b o n d i n g p u r p o s e s , some f i l l e r i s u s u a l l y added t o t h e p h e n o l - f o r m a l d e h y d e r e s i n . B e s i d e s a c t i n g as a s p a c e f i l l e r and r e s i n e x t e n d e r , the f i l l e r h e l p s r e d u c e t h e c o n s i d e r a b l e s h r i n k i n g t h a t t a k e s p l a c e d u r i n g p o l y m e r c r o s s l i n k i n g . Common f i l l e r m a t e r i a l s a r e wood f l o u r , g r o u n d c o r n c o b s and g r o u n d b a r k . The a d d i t i o n of more f o r m a l d e h y d e t o t h e a d h e s i v e i s not r e q u i r e d f o r t h i s t y p e of 23 F i g u r e 1-13. I m p o r t a n t R e a c t i o n s i n P h e n o l - F o r m a l d e h y d e R e s i n F o r m u l a t i o n 24 e F i g u r e 1-14. Q uinone M e t h i d e s as I i n t e r m e d i a t e s i n t h e F o r m a t i o n of a P h e n o l - F o r m a l d e h y d e R e s i n r e s i n . Polymer c u r e o c c u r s by a c o n t i n u a t i o n of t h e c o n d e n s a t i o n r e a c t i o n t o p r o d u c e a h i g h l y c r o s s l i n k e d s t r u c t u r e . Under b a s i c c o n d i t i o n s , any m e t h y l e n e - e t h e r l i n k a g e s p r e s e n t decompose t o a s i m p l e m e t h y l e n e b r i d g e w i t h t h e r e l e a s e of a f o r m a l d e h y d e m o l e c u l e t h a t p a r t i c i p a t e s i n f o r m a t i o n o f more m e t h y l o l g r o u p s . The breakdown r e a c t i o n i s p r o b a b l y a r e v e r s a l of e q u a t i o n I I I i n F i g u r e 1-14 ( 4 3 ) . 25 I-C. W e s t e rn Hemlock Bark as a S o u r c e of C h e m i c a l s Most of the work c a r r i e d out on c o m m e r c i a l c h e m i c a l a p p l i c a t i o n s of w e s t e r n hemlock b a r k was done a t ITT R a y o n i e r , p r i m a r i l y by H e r r i c k and H e r g e r t , a l t h o u g h n e i t h e r of t h e s e a u t h o r s i s p u b l i s h i n g i n t h i s f i e l d now. S e v e r a l e x c e l l e n t r e v i e w s have been w r i t t e n on t h e c h e m i s t r y and u t i l i z a t i o n of w e s t e r n hemlock bark e x t r a c t i v e s ( 1 7 , 2 9 , 4 4 ) . (1) A d h e s i v e A p p l i c a t i o n s I n t h e t a n n i n s d e r i v e d f r o m w e s t e r n hemlock b a r k , t h e A and B p h e n o l i c r i n g s a r e q u i t e d i f f e r e n t i n r e a c t i v i t y . I f a hemlock b a r k e x t r a c t i s s i m p l y mixed w i t h f o r m a l d e h y d e under a l k a l i n e c o n d i t i o n s , the p h l o r o g l u c i n o l - d e r i v e d A - r i n g r e a c t s much f a s t e r t h an th e c a t e c h o l B - r i n g . F i g u r e 1-9 gave t h e r e l a t i v e r e a c t i v i t i e s of t h e s e two p h e n o l i c s ; p h l o r o g l u c i n o l i s a p p r o x i m a t e l y 3 t i m e s more r e a c t i v e t o f o r m a l d e h y d e t h a n c a t e c h o l . A r e s i n made i n t h i s way has a v e r y s h o r t p o t - l i f e and low s t r e n g t h as a wood a d h e s i v e ( 3 9 ) . The f o r m e r i s c a u s e d by t h e h i g h r e a c t i v i t y of t h e A - r i n g , w h i l e th e l a t t e r i s p r o b a b l y due t o t h e l a r g e s i z e o f the t a n n i n m o l e c u l e compared t o t h e r e l a t i v e l y s h o r t m e t h y l e n e b r i d g e s formed between m o l e c u l e s by t h e f o r m a l d e h y d e . Because of t h e s t e r i c ' p r o b l e m s , t h e r e would be r e l a t i v e l y few c o v a l e n t bonds between t a n n i n m o l e c u l e s , f o r m i n g a r a t h e r b r i t t l e t h r e e - d i m e n s i o n a l s t r u c t u r e . 26 A way a r o u n d t h i s p r o b l e m i s t o have l o n g e r , more f l e x i b l e b r i d g i n g between p o l y p h e n o l u n i t s . Low m o l e c u l a r w e i g h t p h e n o l -f o r m a l d e h y d e r e s i n can p e r f o r m t h i s f u n c t i o n . MacLean and G a r d n e r (39) were t h e f i r s t i n v e s t i g a t o r s t o show t h a t s t r o n g , d u r a b l e p l ywood bonds c o u l d be made w i t h s u l p h i t e d w e s t e r n hemlock b a r k e x t r a c t s s u b s t i t u t i n g f o r up t o 75% of t h e p h e n o l - f o r m a l d e h y d e a d h e s i v e . Bonds o b t a i n e d u s i n g an a d h e s i v e n ot f o r t i f i e d w i t h p h e n o l - f o r m a l d e h y d e r e s i n s were not a c c e p t a b l e . L a t e r , H e r r i c k and Bock (40) t r i e d a d i f f e r e n t a p p r o a c h by i n i t i a l l y r e a c t i n g an ammonia e x t r a c t of hemlock bark w i t h t r i m e t h y l o l p h e n o l ( F i g u r e 1-15) t o form an a d h e s i v e . B e s i d e s f o r m i n g a l a r g e r and more f l e x i b l e b r i d g i n g u n i t , t h e C H 2 O H F i g u r e 1-15. S t r u c t u r e of T r i m e t h y l o l p h e n o l t r i m e t h y l o l p h e n o l t i e s up t h e h i g h l y r e a c t i v e p o s i t i o n on t h e t a n n i n A - r i n g , p r o b a b l y a l l o w i n g t h e c a t e c h o l B - r i n g t o r e a c t ' a s w e l l . A r e s i n made from 49% bark e x t r a c t , 34% 27 p o l y m e t h o l y l p h e n o l and 17% f i l l e r was f a s t - c u r i n g and p r o d u c e d a c c e p t a b l e e x t e r i o r - g r a d e p l y w o o d . At t h e t i m e t h e s e a d h e s i v e s were d e v e l o p e d , c o m m e r c i a l a p p l i c a t i o n was not f e a s i b l e b e c a u s e of t h e h i g h c o s t o f t h e bark e x t r a c t compared t o t h e c o s t of p h e n o l . R a y o n i e r had a p i l o t p l a n t p r o d u c i n g t h e ammonia hemlock b a r k e x t r a c t f o r a b o u t 10 c e n t s p e r pound ( i n 1958) ( 4 0 ) . U n f o r t u n a t e l y , a t t h a t t i m e p h e n o l was even c h e a p e r a t a b o u t 9 c e n t s p e r pound ( 4 5 ) . In o r d e r t o a v o i d t h i s c o s t p r o b l e m , H e r r i c k and Conca (46) d e v e l o p e d a c o l d - s e t t i n g r e s i n u s i n g an ammonia e x t r a c t of hemlock b a r k . As a c o l d - s e t t i n g r e s i n , t h e t a n n i n a d h e s i v e would compete a g a i n s t t h e more e x p e n s i v e PRF a d h e s i v e s . I t was f o u n d t h a t a maximum of 30% o f a PRF r e s i n o r 60% of an RF r e s i n c o u l d be s u b s t i t u t e d w i t h t h e t a n n i n e x t r a c t and s t i l l meet p o t -l i f e and a s s e m b l y - t i m e r e q u i r e m e n t s . A d d i t i o n a l r e s i n components s u c h as p o l a r o r g a n i c s o l v e n t s and p H - r e g u l a t i n g b u f f e r s had t o be added t o t h e a d h e s i v e mix t o a c c o m p l i s h t h i s . The e c o n o m i c s i n t h i s c a s e were not much more f a v o r a b l e . L a m i n a t i n g PRF r e s i n i s n o r m a l l y 30%-40% p h e n o l , so t h e e x t r a c t i s p r i m a r i l y s u b s t i t u t i n g f o r p h e n o l , w h i c h was l e s s e x p e n s i v e t h a n t h e e x t r a c t anyway. In o r d e r t o p r o d u c e t h e bark e x t r a c t f o r a r e a s o n a b l e p r i c e (12.5 c e n t s / l b . i n 1960), t h e e x t r a c t i o n p l a n t - would have t o be b u i l t on a f a i r l y l a r g e s c a l e (19 MM l b s . / y r . ) ( 4 6 ) . To j u s t i f y b u i l d i n g s u c h a p l a n t , a market f o r t h e p r o d u c t would have t o be d e v e l o p e d f i r s t . T h i s market n e v e r d e v e l o p e d , p r o b a b l y b e c a u s e g l u l a m lumber i s s u c h a h i g h l i a b i l i t y p r o d u c t . M a n u f a c t u r e r s would not want t o t a k e any 28 c h a n c e s on u s i n g an u n p r o v e n a d h e s i v e . The p r i c e of p h e n o l d e c r e a s e d u n t i l t h e p e t r o l e u m s h o r t a g e s of 1973-1974 ( F i g u r e 1-16). C o n s e q u e n t l y , not much work was 90+ 80- • 70' • 60- • 50' • LU O 30-20- • Benzene,Cents/Gallon i t Phenol, Cents/Pound Resin,(40 %), Cents/Pound \ V /.<•"--— Ji I I 1—'-I H -I I •+ 63 64 65 66 67 68 69 70 71 72 73 74 75 76 YEAR F i g u r e 1-16. P r i c e s of Benzene, P h e n o l and PF R e s i n from 1963 t o 1975 (45) done i n u t i l i z a t i o n of b a r k e x t r a c t s i n a d h e s i v e s d u r i n g t h i s t i m e . When i t a p p e a r e d t h a t bark e x t r a c t s might become c o s t -c o m p e t i t i v e w i t h p h e n o l , i n t e r e s t i n t h i s a r e a was renewed. 29 A n d e r s o n e t a l . (47) d e s c r i b e d an a p p l i c a t i o n t o p a r t i c l e b o a r d . The p a r t i c l e s were f i r s t s p r a y e d w i t h c o n c e n t r a t e d s u l p h i t e bark e x t r a c t , t h e n mixed w i t h powdered p a r a f o r m a l d e h y d e ( a p p r o x i m a t e l y 1 1/2% of f u r n i s h w e i g h t ) and p r o c e s s e d i n t o a b o a r d . In t h e h o t - p r e s s , f o r m a l d e h y d e i s r e l e a s e d w h i c h r e a c t s w i t h t h e p h e n o l i c bark e x t r a c t t o form a bond. The b o a r d s p r o d u c e d were c o m p a r a b l e t o c o n v e n t i o n a l p h e n o l i c - r e s i n bonded e x t e r i o r - g r a d e p a r t i c l e b o a r d . In a p a r t i c l e b o a r d a p p l i c a t i o n , th e p r o b l e m s of s h o r t p o t l i f e and p o o r wet s t r e n g t h a s s o c i a t e d w i t h w e s t e r n hemlock t a n n i n a d h e s i v e s a r e m i n i m i z e d . T h i s may y e t p r o v e t h e b e s t a p p l i c a t i o n f o r t h i s t y p e of a d h e s i v e . On t h e b a s i s of d i f f e r e n t i a l t h e r m a l a n a l y s i s and plywood b o n d i n g t e s t s , S t e i n e r and Chow (48) c o n c l u d e d t h a t an a d h e s i v e made from w e s t e r n hemlock e x t r a c t s r e q u i r e d h i g h e r ' t h a n c o n v e n t i o n a l t e m p e r a t u r e s t o p r o v i d e s u f f i c i e n t c r o s s - l i n k i n g f o r an a c c e p t a b l e bond. The a d h e s i v e was made from a water e x t r a c t of f r e s h w e s t e r n hemlock bark and p a r a f o r m a l d e h y d e , and the pH a d j u s t e d t o about 6.8 j u s t p r i o r t o s p r e a d i n g . E x t e r i o r -g r a d e bonds were o b t a i n e d w i t h a p r e s s - t e m p e r a t u r e of 180° C and a p r e s s t i m e of 7.5 m i n u t e s . A t y p i c a l p r e s s - t e m p e r a t u r e f o r PF r e s i n - b a s e d a d h e s i v e u s e d f o r plywood m a n u f a c t u r e i s 150° C. I t was a l s o o b s e r v e d t h a t t h e age of t h e bark and e x t r a c t i o n method had a g r e a t i n f l u e n c e on t h e q u a l i t y of t h e bond p r o d u c e d . The v a r i a b i l i t y of b a r k q u a l i t y w i l l p r o b a b l y p r o v e t o be the b i g g e s t o b s t a c l e t o i t s l a r g e s c a l e ' U t i l i z a t i o n . F o r ply w o o d a p p l i c a t i o n s , t h e p r o b l e m o f t h e s h o r t p o t l i f e c a n be r e m e d i e d by u s i n g slow r e l e a s i n g f o r m a l d e h y d e s o u r c e s such, as 30 p a r a f o r m a l d e h y d e or hexamine (39) or a d d i n g o r g a n i c s o l v e n t s t o t h e a d h e s i v e mix ( 4 6 ) , w h i l e r e a s o n a b l y good bonds can be o b t a i n e d w i t h h i g h p r e s s t e m p e r a t u r e s (48) a n d / o r l i m i t e d f o r t i f i c a t i o n w i t h c o n v e n t i o n a l PF r e s i n ( 4 0 ) . However, i t i s much more' d i f f i c u l t t o g e t a r o u n d t h e p r o b l e m of l o g t o l o g v a r i a t i o n i n bark q u a l i t y due t o i n h e r e n t t r e e d i f f e r e n c e s s u c h as age, bark t h i c k n e s s and p e r c e n t a g e o u t e r b a r k , o r d i f f e r e n c e s i n t h e t r e a t m e n t a f t e r h a r v e s t i n g , l i k e water o r d r y s o r t i n g , l e n g t h o f t i m e i n s t o r a g e and whether th e l o g i s d e b a r k e d m e c h a n i c a l l y or h y d r a u l i c a l l y ( 4 8 , 4 4 ) . The a p p r o a c h t a k e n i n t h i s t h e s i s of d e g r a d i n g t h e t a n n i n s t o s i m p l e r components s t a b i l i z e s t h e q u a l i t a t i v e n a t u r e of t h e p r o d u c t s o b t a i n e d , a l t h o u g h t h e i r y i e l d w i l l v a r y . T h i s i s a d v a n t a g e o u s i n c o n t r o l l i n g t h e q u a l i t y of t h e a d h e s i v e s t o be made i n any c o m m e r c i a l a p p l i c a t i o n . (2) N o n - A d h e s i v e A p p l i c a t i o n s The n o n - c h e m i c a l a p p l i c a t i o n s of c o n i f e r bark a r e q u i t e e x t e n s i v e but w i l l not be d e s c r i b e d h e r e . S e v e r a l good r e v i e w s on t h i s t o p i c a r e a v a i l a b l e ( 7 , 5 0 , 5 1 ) . C o m m e r c i a l c h e m i c a l p r o d u c t s have been p r o d u c e d from t h e b a r k s o f t h r e e N o r t h A m e r i c a n c o n i f e r s - redwood ( S e q u o i a  s e m p e r v i r e n s (D. Don) E n d l . ) , D o u g l a s f i r and w e s t e r n hemlock. D o u g l a s f i r has s u b s t a n t i a l amounts o f wax a s s o c i a t e d w i t h t h e b a r k p h e l l e m , t h a t was a t one t i m e p r o d u c e d c o m m e r c i a l l y by t h e 31 Bohemian Lumber Company i n Oregon ( 4 9 ) . Many p r o d u c t s b a s e d on th e p o l y p h e n o l i c p o r t i o n of t h e s e t h r e e b a r k s were p r o d u c e d and a r e summarized i n T a b l e 1-3. D o u g l a s f i r i s e x c l u d e d from t h i s t a b l e b e c a u s e W e y e r h a e u s e r , t h e p r o d u c i n g company, d i d not p u b l i s h any i n f o r m a t i o n on a v a i l a b i l i t y o r a p p l i c a t i o n s f o r t h e i r b a r k p r o d u c t s . I t i s p r o b a b l e t h a t t h e s e p r o d u c t s were c o m m e r c i a l l y a v a i l a b l e f o r o n l y a s h o r t t i m e . H e r g e r t (17) i n f e r s t h a t t h i s may have been due t o u n d e s i r a b l e f o a m i n g i n t h e D o u g l a s f i r b a r k e x t r a c t i n d r i l l i n g mud and b o i l e r water a p p l i c a t i o n s . T h i s c o u l d have been c a u s e d by t h e h i g h c o n c e n t r a t i o n of f a t t y a c i d s i n t h e s p e c i e s . M a n u f a c t u r e of t h e redwood b a r k p r o d u c t s was d i s c o n t i n u e d i n t h e l a t e s i x t i e s . They were a l s o a v a i l a b l e f o r o n l y a s h o r t t i m e ( 1 7 ) . The commitment of ITT R a y o n i e r t o t h e i r b a r k u t i l i z a t i o n p r o g r a m was r e a l l y q u i t e r e m a r k a b l e . The program s t a r t e d i n 1948 and f o r some t i m e had two c o m m e r c i a l e x t r a c t i o n p l a n t s o p e r a t i n g . The V a n c o u v e r , B.C. p l a n t was i n o p e r a t i o n from 1956 t o 1976, p r o d u c i n g between 5000 t o 7600 t o n n e s / y e a r , p r i m a r i l y of s u l p h i t e d e x t r a c t ( 4 4 ) . C o m m e r c i a l p r o d u c t i o n a t th e G r a y s H a r b o r p l a n t e x t e n d e d from 1967 t o 1972 ( 4 4 ) . The b a r k u t i l i z a t i o n program a t R a y o n i e r was t e r m i n a t e d i n t h e l a t e s e v e n t i e s . " R a y f l o " , t h e d r i l l i n g mud a d d i t i v e , was by f a r t h e most s u c c e s s f u l p r o d u c t m a r k e t e d . When t h e s u l p h o n a t e d e x t r a c t i s added t o t h e c l a y s l u r r i e s used t o l u b r i c a t e t h e d r i l l , t h e mud becomes l e s s v i s c o u s and more s l i p p e r y . R a y f l o i s a s u l p h o n a t e d p o l y f l a v a n o i d o b t a i n e d by e x t r a c t i n g g r o u n d b a r k w i t h a water 32 Spec i e s Name Type of E x t r a c t A p p l i c a t i o n R e d w o o d 1 1 1 Bark P a l c o t a n S u l f i t e D r i l l i n g mud a d d i t i v e P a l c o n a t e NaOH B o i l e r and c o o l i n g w ater t r e a t m e n t W e s t e r n ( 2 ' Hemlock R a y f l o R a y f l o - C S u l f i t e S u l f i t e D r i l l i n g mud a d d i t i v e B o i l e r and c o o l i n g w ater t r e a t m e n t R a y p l e x S u l f i t e Zn,Fe,Cu and Mn m i c r o n u t r i e n t d e f i c i e n c i e s HT-120 Ammon i a R e s i n i n t e r m e d i a t e s T e r r a n i e r Ammon i a C h e m i c a l g r o u t i n g s y s t e m LB 451A S u l f i t e P e n e t r a n t i r o n s p r a y f o r c h l o r a t i c c i t r u s t r e e s ( 1 ) M a n u f a c t u r e d by P a c i f i c Lumber Co., S c o t i a C a l i f . M a n u f a c t u r e d by ITT R a y o n i e r I n c . , a t G r a y s H a r b o r , Wash., and by R a y o n i e r Canada L t d . a t V a n c o u v e r , B.C. T a b l e 1-3. Co m m e r c i a l P o l y f l a v a n o i d P r o d u c t s (17,40,44,46) s o l u t i o n o f 10-18% sodium s u l p h i t e and b i s u l p h i t e a t 150° C. The y i e l d o f t h i s p r o d u c t from b a r k was about 35% ( 5 0 ) . The s t r u c t u r e of s u l p h o n a t e d t a n n i n s was i n v e s t i g a t e d by 33 S e a r s ( 5 2 ) . By s u b j e c t i n g c a t e c h i n t o t h e same r e a c t i o n c o n d i t i o n s u s e d t o s u l p h o n a t e a n d , e x t r a c t bark t a n n i n s , he f o u n d t h a t t h e p y r a n C - r i n g of t h e model compound i s opened and a s u l p h i t e g r o u p added t o c a r b o n - 2 ( F i g u r e 1-17). I t i s p r o b a b l e t h a t t h e s u l p h o n a t e d b a r k t a n n i n s have s i m i l a r r i n g - o p e n e d c a t e c h i n or e p i c a t e c h i n m o i e t i e s ' i n i t s po l y m e r s t r u c t u r e . F i g u r e 1-17. S u l p h o n a t i o n of C a t e c h i n R a y f l o was shown t o be s u p e r i o r t o q u e b r a c h o wood e x t r a c t w h i c h was t h e s t a n d a r d a d d i t i v e a t t h e time ( 9 , 5 3 ) . T h i s p r o d u c t e v e n t u a l l y became u n e c o n o m i c a l t o m a n u f a c t u r e , b e c a u s e of c o m p e t i t i o n from c h e a p e r a d d i t i v e s d e r i v e d from 1 i g n o s u l p h o n a t e s 34 (44) . " R a y p l e x " i s a s i m i l a r s u l p h i t e d e x t r a c t and was p r e p a r e d as a complex of v a r i o u s m e t a l s a l t s i n t h e form of a c h e l a t e ( 5 4 ) . T h i s m a t e r i a l was u s e d as a s o u r c e of m i c r o n u t r i e n t s i n a g r i c u l t u r a l a p p l i c a t i o n s . I t c o u l d be a p p l i e d as a f o l i a r s p r a y o r i n t h e s o i l t o f i e l d and o r c h a r d c r o p s d e f i c i e n t i n one or more m i n e r a l n u t r i e n t s . Some of t h e m e t a l s t h a t c o u l d be s u p p l i e d i n t h i s way were z i n c , i r o n , c o p p e r and manganese. A l t h o u g h t h i s p r o d u c t had a low d e g r e e of p h y t o t o x i c i t y ( 4 4 ) , i t had t o be a p p l i e d e a r l y i n t h e g r o w i n g s e a s o n i n o r d e r t o a v o i d f r u i t s t a i n . I f hemlock bark i s e x t r a c t e d w i t h aqueous ammonia, a m a t e r i a l w i t h q u i t e d i f f e r e n t p r o p e r t i e s r e s u l t s . The e x t r a c t i s o b t a i n e d i n 25-30% y i e l d and has t h e a b i l i t y t o complex w i t h i r o n , chromium and o t h e r m e t a l i o n s t o g i v e g e l s . An e x t r a c t of t h i s t y p e i s a l s o r e a c t i v e w i t h f o r m a l d e h y d e . B e s i d e s b e i n g d e v e l o p e d f o r a d h e s i v e a p p l i c a t i o n s as d e s c r i b e d e a r l i e r , t h i s e x t r a c t c o u l d be u s e d i n c h e m i c a l g r o u t i n g s y stems f o r s o i l s t a b i l i z a t i o n and c o n t r o l of w ater f l o w on heavy c o n s t r u c t i o n s i t e s . Examples would be deep e x c a v a t i o n s , d r i v i n g t u n n e l s or s t r e e t s , and e a r t h - f i l l dams. The b a r k e x t r a c t i s d i s s o l v e d i n w a t e r , mixed w i t h a s o l u t i o n c o n t a i n i n g f o r m a l d e h y d e and m e t a l s a l t , t h e n pumped t h r o u g h an i n j e c t i o n p i p e i n t o the s o i l t o be g r o u t e d . A f t e r s e t t l i n g , t h e s t a b i l i z e d s o i l has i n c r e a s e d l o a d b e a r i n g c a p a c i t y , r e d u c e d water p e r m e a b i l i t y and more s t a b i l i t y t o m i n i m i z e d e f o r m a t i o n and s u b s i d e n c e ( 1 7 , 4 4 ) . A l t h o u g h t h i s s y s t e m worked w e l l and was c o m p e t i t i v e w i t h o t h e r p r o d u c t s , s o i l 35 g r o u t i n g n e v e r became a common p r o c e d u r e i n N o r t h A m e r i c a , and so a market n e v e r d e v e l o p e d . However, c h e m i c a l g r o u t i n g has d e v e l o p e d i n t o a f a i r l y r o u t i n e p r o c e d u r e i n E u r o p e ( 4 4 ) . As an a d d i t i v e f o r b o i l e r and c o o l i n g w a t e r , t h e s u l p h i t e d e x t r a c t s worked w e l l as d i s p e r s a n t s for. s c a l e - f o r m i n g m i n e r a l s and c o r r o s i o n i n h i b i t o r s ( 4 4 ) . However, t h i s i s q u i t e a l i m i t e d market and c o u l d not s u p p o r t an e x t r a c t i o n p l a n t i f t h e r e were no o t h e r i m p o r t a n t m a r k e t s f o r bark c h e m i c a l s . I t i s a p p a r e n t t h a t a l t h o u g h t h e r e have been some s u c c e s s f u l c o m m e r c i a l c h e m i c a l a p p l i c a t i o n s of w e s t e r n hemlock bark and i t s e x t r a c t s , t h e y have a l l been of low volume, and p r o b a b l y r e a l i z e d o n l y a s m a l l p r o f i t . P o t e n t i a l l y , t h e b e s t a p p l i c a t i o n i s s t i l l as a wood a d h e s i v e . T h i s would c e r t a i n l y be a l a r g e s c a l e use, and i n a l a r g e f o r e s t - p r o d u c t s company a b ark b a s e d a d h e s i v e c o u l d be p r o d u c e d and u t i l i z e d i n t e r n a l l y , r e d u c i n g t h e company's dependence on e x t e r n a l s u p p l y s o u r c e s . I-D. Bark P o l y f l a v a n o i d s of O t h e r S p e c i e s ; C h e m i s t r y and U t i l i z a t i o n i n A d h e s i v e s The b a r k p o l y f l a v a n o i d s from a number of t r e e s p e c i e s b e s i d e s w e s t e r n hemlock have been i n v e s t i g a t e d f o r t h e i r s u i t a b i l i t y i n a d h e s i v e f o r m u l a t i o n . T hese i n c l u d e t h e s o u t h e r n p i n e s , P i n u s r a d i a t a D. Don, A c a c i a ( w a t t l e ) s p e c i e s , mangrove s p e c i e s ( 5 5 , 5 6 ) , F i n n i s h s p r u c e ( P i c e a o b o v a t a v a r . f e n n i c a ( R e g e l ) H e n ry) ( 5 7 ) , P i n u s b r u t i a T e n . ( 5 8 ) , and L a r i x 36 l e p t o l e p s i s G o r d . ( 5 9 ) . The b u l k of t h e l i t e r a t u r e i s c o n c e r n e d w i t h t h e f i r s t t h r e e s p e c i e s or s p e c i e s g r o u p s . F i g u r e 1-18 shows t h e s u b s t i t u t i o n p a t t e r n s f o u n d i n t h e p o l y f l a v a n o i d s of t h e i m p o r t a n t bark e x t r a c t s . The i m p o r t a n t d i f f e r e n c e s a r e t h a t w a t t l e t a n n i n has r e s o r c i n o l i c A - r i n g s a l o n g w i t h B - r i n g s d e r i v e d from p y r o g a l l o l or c a t e c h o l , w h i l e t h e c o n i f e r s ( i n c l u d i n g w e s t e r n hemlock) have p h l o r o g l u c i n o l -d e r i v e d A - r i n g s and c a t e c h o l B - r i n g s . The s u b s t i t u t i o n p a t t e r n s of t h e p h e n o l i c r i n g s have a l a r g e e f f e c t on t h e r e a c t i v i t y of the t a n n i n s t o f o r m a l d e h y d e and hence t o i t s s u i t a b i l i t y a s an a d h e s i v e . A n o t h e r i m p o r t a n t f a c t o r i s the a v e r a g e m o l e c u l a r w e i g h t . Some d a t a have been p u b l i s h e d on t h e m o l e c u l a r w e i g h t r a n g e s of ba r k p o l y p h e n o l s ( s e e T a b l e 1 - 4 ) , but t h e s e f i g u r e s need c a r e f u l i n t e r p r e t a t i o n . T h e r e i s e v i d e n c e t h a t i n aqueous s o l u t i o n , t a n n i n m o l e c u l e s t e n d t o a s s o c i a t e t o g i v e a p p a r e n t m o l e c u l a r w e i g h t s much g r e a t e r t h a n t h e a c t u a l m o l e c u l a r w e i g h t ( 6 0 ) . However, s i n c e i t i s t h e s e a g g r e g a t e s t h a t g i v e t a n n i n s o l u t i o n s t h e i r v i s c o s i t y and r e a c t i v i t y c h a r a c t e r i s t i c s , t h e r e p o r t e d f i g u r e s may be more u s e f u l from a p r a c t i c a l p o i n t of v i e w . Some a d h e s i v e a p p l i c a t i o n s of t h e s o u t h e r n p i n e s , P i n u s  r a d i a t a , and w a t t l e bark e x t r a c t s a r e g i v e n below. 37 (X s u b s t i t u e n t s r e f e r t o p o s s i b l e c o n t i n u a t i o n s o f t h e p o l y m e r c h a i n ) E x t r a c t S u b s t i t u e n t R e l a t i v e Amount R e f e r e n c e s RI R2 R3 W a t t l e H OH OH 70% 61 ,62 H OH H 25% OH OH H 5% OH OH OH T r a c e S o u t h e r n P i n e OH OH H 63,64,65 P i n u s r a d i a t a OH OH H major 65,66,67 OH OH OH minor OH H H T r a c e Mangrove OH OH OH • 67 OH * OH H F i g u r e 1-18. S u b s t i t u t i o n P a t t e r n s i n t h e B a s i c U n i t s of Bark P o l y f l a v a n o i d s 38 S o u r c e of Bark Tann i n M o l e c u l a r Weight R e f e r e n c e W a t t l e Mn = 1250 Range=500(n=2) t o 3000 (n=10 t o 11) 68 S h o r t l e a f and L o b l o l l y p i n e • ( s o u t h e r n p i n e s ) <3500 - 50-60% 3500-8000 - 20% 12,000 - 10-20% 63,69 R a d i a t a p i n e Mn = 8400 70 <10 3 = 31.4% 10 3 - 10 * = 11.5% 10 a - 10 5 = 29.2% 1 0 5 - 1 0 s = 5.5% >10 6 = 22.4% 71 T a b l e 1-4. M o l e c u l a r W e i g h t s and D i s t r i b u t i o n s of Bark P o l y p h e n o l s (1) W a t t l e In 1982 i t was r e p o r t e d t h a t a p p r o x i m a t e l y 300,000 t o n s of c o n d e n s e d t a n n i n s were p r o d u c e d c o m m e r c i a l l y w o r l d - w i d e , of wh i c h o n l y 15,000 t o n s were us e d f o r a d h e s i v e p u r p o s e s ( 6 5 ) . Most, or a l l , of t h e t a n n i n u s e d f o r a d h e s i v e s was from t h e bark of t h e b l a c k w a t t l e t r e e (Acac i a m e a r n s i i De W i l d . ) . The d e v e l o p m e n t o f plywood, p a r t i c l e b o a r d , g l u l a m , c a r d b o a r d and f i n g e r - j o i n t i n g a d h e s i v e s from t h e p o l y f l a v a n o i d s o f t h i s s p e c i e s has m a i n l y been i n S o u t h A f r i c a . T h e r e a r e a number of r e a s o n s why t h e s e a p p l i c a t i o n s have been s u c c e s s f u l . (1) W a t t l e t a n n i n s have p r i m a r i l y a r e s o r c i n o l i c A - r i n g , w h i c h has a r e l a t i v e l y low r e a c t i v i t y w i t h f o r m a l d e h y d e , and a l l o w s a much g r e a t e r d e g r e e of c o n t r o l o v e r t h e t a n n i n -39 f o r m a l d e h y d e c o n d e n s a t i o n r e a c t i o n ( as compared t o t h e c o n i f e r t a n n i n s ) . (2) They have a c o m p a r a t i v e l y low a v e r a g e m o l e c u l a r w e i g h t . (3) A w e l l e s t a b l i s h e d t a n n i n i n d u s t r y e x i s t s i n S o u t h A f r i c a a l r e a d y p r o d u c i n g b a r k e x t r a c t f o r o t h e r a p p l i c a t i o n s . (4) C o n v e n t i o n a l p h e n o l i c r e s i n s or t h e i r raw m a t e r i a l s have t o be i m p o r t e d i n t o S o u t h A f r i c a r e s u l t i n g i n a h i g h l o c a l c o s t . The e c o n o m i c s of p r o d u c i n g a t a n n i n - b a s e d a d h e s i v e become more a t t r a c t i v e f o r t h i s r e a s o n . U n m o d i f i e d t a n n i n r e s i n s a r e o f t e n u n s u i t a b l e f o r p a r t i c l e b o a r d a p p l i c a t i o n s b e c a u s e of t h e h i g h v i s c o s i t y when c o n c e n t r a t e d t o 50 or 60% s o l i d s . T h i s p r o b l e m has been c o r r e c t e d by s u l p h o n a t i o n ( 6 8 ) , h e a t i n g w i t h base (72) o r t r e a t m e n t w i t h a s e r i e s of a c i d and a l k a l i n e s t e p s t h a t h y d r o l y s e t h e v i s c o s i t y - i n f l u e n c i n g c a r b o h y d r a t e gums t o s i m p l e s u g a r s ( 7 3 ) . M o d i f i e d t a n n i n e x t r a c t has a l s o been combined w i t h u r e a - f o r m a l d e h y d e p r e p o l y m e r t o g i v e a s t r o n g e r but l e s s w a t e r p r o o f p a r t i c l e b o a r d , p r i m a r i l y u s e d f o r f l o o r i n g ( 7 4 ) . P a r t i c l e b o a r d m a n u f a c t u r e has been t h e l a r g e s t consumer of w a t t l e t a n n i n a d h e s i v e s ( 6 5 ) . In some c a s e s , i t has been r e p o r t e d t h a t t h e p r o d u c t i s s u p e r i o r t o c o n v e n t i o n a l PF bonded p a r t i c l e b o a r d i n r e s i s t a n c e t o w e a t h e r i n g and d i m e n s i o n a l s t a b i l i t y ( 7 2 ) . T a n n i n a d h e s i v e s u s e d f o r e x t e r i o r - g r a d e plywood m a n u f a c t u r e a r e u s u a l l y f o r t i f i e d w i t h 10% t o 25% of c o n v e n t i o n a l a d h e s i v e s . PRF ( 7 5 ) , PF (76) and UF (77) r e s i n s have a l l been shown t o a c t as good c r o s s l i n k i n g a g e n t s f o r 40 w a t t l e t a n n i n - b a s e d a d h e s i v e s , and f o r m u l a t i o n s u s i n g t h e s e r e s i n s have been i n use i n d u s t r i a l l y ( 6 5 ) . U n f o r t i f i e d f o r m u l a t i o n s have a l s o been d e v e l o p e d f o r p lywood a p p l i c a t i o n s ( 7 2 , 7 8 ) . One p a r t i c u l a r l y i n t e r e s t i n g r e s i n i n c o r p o r a t e s z i n c a c e t a t e t h a t a c t s as an a c c e l e r a t o r of t h e r e a c t i o n between t a n n i n and f o r m a l d e h y d e , and as a B - r i n g a c t i v a t o r t o p r o v i d e a d d i t i o n a l c r o s s - l i n k i n g ( 7 9 ) . A t y p i c a l f o r m u l a t i o n would have 15 t o 16% p a r a f o r m a l d e h y d e as h a r d e n e r and 10 t o 25% c o c o n u t s h e l l f l o u r ( o r s i m i l a r p r o d u c t ) as a f i l l e r , b a s e d on t h e w e i g h t o f t a n n i n s o l i d s ( 6 5 ) . A number of c o l d - s e t t i n g w a t t l e t a n n i n - b a s e d a d h e s i v e s f o r g l u l a m a p p l i c a t i o n s have been d e s c r i b e d . A s y s t e m b a s e d on t h e r e a c t i o n of r e s o r c i n o l w i t h m e t h y l o l - t a n n i n ( f o r m e d by r e a c t i o n of w a t t l e t a n n i n w i t h f o r m a l d e h y d e i n 50% m e t h a n o l s o l u t i o n ) has been d e s c r i b e d ( 7 2 ) . I t was l a t e r f o u n d t h a t i f t h e t a n n i n e x t r a c t i s f i r s t r e a c t e d w i t h s u l p h i t e i n o r d e r t o open t h e p y r a n C - r i n g , t h e amount of added r e s o r c i n o l can be r e d u c e d t o 10% of t h e t o t a l l i q u i d a d h e s i v e ( 8 0 ) . T h i s c o n c e n t r a t i o n of r e s o r c i n o l i s s u b s t a n t i a l l y l o w e r than what i s r e q u i r e d i n c o n v e n t i o n a l PRF r e s i n s . PRF i s a l s o t h e r e s i n n o r m a l l y u s e d f o r f i n g e r - j o i n t i n g . However, i t s use i s not p r a c t i c a l where l a r g e p r e s s e s a r e not a v a i l a b l e , as t h e s e t t i n g t i m e i s q u i t e l e n g t h y a t ambient t e m p e r a t u r e s . V e r y f a s t s e t t i n g a d h e s i v e s u s i n g w a t t l e t a n n i n s have been d e v e l o p e d t h a t a r e v a r i a t i o n s of t h e "honeymoon" r e s i n s d e s c r i b e d by K r i e b i c h ( 8 1 ) . These a r e two component s y s t e m s where one p a r t i s a c o n v e n t i o n a l s l o w - s e t t i n g PRF or 41 t a n n i n / f o r m a l d e h y d e r e s i n w i t h an e x c e s s of h a r d e n e r , and t h e o t h e r p a r t i s a v e r y r e a c t i v e p h e n o l i c or t a n n i n r e s i n a t a h i g h pH w i t h no h a r d e n e r ( 8 2 , 8 3 , 8 4 ) . These a d h e s i v e s a l l o w h a n d l i n g of t h e g l u e d lumber w i t h i n one hour of m a n u f a c t u r e . Some s u c c e s s f u l minor a p p l i c a t i o n s of w a t t l e t a n n i n s a r e i n a d h e s i v e s f o r d a m p - r e s i s t a n t c a r d b o a r d ( 8 5 ) , p h e n o l i c foams (86) and i n t a n n i n b a s e d p o l y u r e t h a n e a d h e s i v e s ( 8 7 ) . (2) S o u t h e r n P i n e s A l t h o u g h q u i t e a b i t of work has been done on e l u c i d a t i o n of t h e s t r u c t u r e of p o l y f l a v a n o i d s i n s o u t h e r n p i n e b a r k s (25,26,27,28), t h e r e has been r e l a t i v e l y l i t t l e i n f o r m a t i o n p u b l i s h e d on f o r m u l a t i n g a d h e s i v e s w i t h bark e x t r a c t s from t h e s e s p e c i e s . Chen r e p o r t s r e p l a c i n g 20% (88) and 40% (89) o f t h e p h e n o l i n a c o m m e r c i a l PF r e s i n w i t h a l k a l i n e e x t r a c t s of s o u t h e r n p i n e s . In b o t h c a s e s , bond s t r e n g t h s c o m p a r a b l e t o c o m m e r c i a l PF r e s i n c o u l d be a c h i e v e d . At t h e h i g h e r s u b s t i t u t i o n l e v e l , t h e mixed r e s i n gave s u p e r i o r r e s u l t s a t s h o r t e r p r e s s t i m e s . The use of a l k a l i n e e x t r a c t s from v a r i o u s a g r i c u l t u r a l r e s i d u e s as p h e n o l i c e x t e n d e r s was a l s o r e p o r t e d i n t h e same p a p e r s . T a n n i n i n t e r f l a v a n o i d bonds a r e p r o n e t o c l e a v a g e under a c i d i c c o n d i t i o n s ( 6 8 , 9 0 ) . I f a s t r o n g n u c l e o p h i l e , s u c h as a t h i o l or p h l o r o g l u c i n o l , i s p r e s e n t , t h a t compound can add t o t h e 4 p o s i t i o n of t h e c l e a v e d f l a v a n o i d u n i t ( 9 1 ) . U s i n g 42 r e s o r c i n o l as t h e n u c l e o p h i l e , Hemingway (92) r e p o r t s f o r m u l a t i n g a c o l d - s e t t i n g g l u l a m a d h e s i v e w i t h c o n d e n s e d p i n e b a r k t a n n i n r e s o r c i n o l a d d u c t s ( F i g u r e 1-19) r e p l a c i n g more t h a n 60% of t h e r e s o r c i n o l i n a c o n v e n t i o n a l PRF r e s i n . The main b e n e f i t of t h i s t r e a t m e n t i s a r e d u c t i o n i n v i s c o s i t y due t o t h e c l e a v a g e of some i n t e r f l a v a n o i d bonds. A r e c e n t economic f e a s i b i l i t y s t u d y has shown t h a t t h e use o f a l k a l i or s u l p h i t e e x t r a c t s of p i n e bark as a p a r t i a l r e p l a c e m e n t f o r PF r e s i n s i n p a r t i c l e b o a r d m a n u f a c t u r e can be e c o n o m i c a l l y j u s t i f i e d . However, f u r t h e r r e s e a r c h i n t o a d h e s i v e f o r m u l a t i o n s f o r t h i s a p p l i c a t i o n t h a t w i l l meet i n d u s t r i a l s t a n d a r d s s t i l l needs t o be done ( 9 3 ) . 43 (3) R a d i a t a P i n e The p r o b l e m s f o u n d w i t h u s i n g P i n u s r a d i a t a b a r k e x t r a c t s i n wood a d h e s i v e s a r e t h e same as t h o s e a s s o c i a t e d w i t h o t h e r c o n i f e r s , namely: (1) S h o r t p o t l i f e . (2) H i g h v i s c o s i t y of t h e a d h e s i v e mix a t c o n v e n t i o n a l s o l i d s c o n t e n t and c o n d i t i o n s . (3) R e l a t i v e l y low s t r e n g t h and water r e s i s t a n c e . A t t e m p t s t o c i r c u m v e n t t h e s e p r o b l e m s go back t o 1952 when D a l t o n (94) u s e d s u l p h o n a t i o n t o r e d u c e t h e v i s c o s i t y and r e a c t i v i t y of r a d i a t a p i n e e x t r a c t s . T h i s a u t h o r r e p o r t e d s t r o n g w a t e r - r e s i s t a n t g l u e l i n e s i n plywood made w i t h t h e m o d i f i e d e x t r a c t , p a r a f o r m a l d e h y d e and a f i l l e r . P a r t i c l e b o a r d a d h e s i v e s made w i t h s i m i l a r e x t r a c t s have a l s o been d e s c r i b e d (95) . U l t r a f i l t r a t i o n has been e v a l u a t e d as a means of p u r i f y i n g r a d i a t a b a r k p o l y p h e n o l s . T h i s p r o c e s s removes t h e h i g h e r m o l e c u l a r w e i g h t f l a v a n o i d f r a c t i o n s t h a t c o n t r i b u t e t o t h e v i s c o s i t y and r e a c t i v i t y p r o b l e m s ( 7 1 , 9 6 ) . The t r e a t m e n t does a p p e a r t o improve the c h a r a c t e r i s t i c s of t h e e x t r a c t , a l t h o u g h t h e r e have been d o u b t s e x p r e s s e d as t o how f e a s i b l e s u c h a t r e a t m e n t c o u l d be on a l a r g e s c a l e i n d u s t r i a l b a s i s ( 9 7 ) . R e c e n t l y P i z z i (97) has s u g g e s t e d t h a t a d i p h e n y l m e t h a n e d i i s o c y a n a t e (MDI) ( s e e F i g u r e 1-20) f o r t i f i e d t a n n i n a d h e s i v e c o u l d be c o n s i d e r e d as a " u n i v e r s a l " t a n n i n a d h e s i v e f o r p a r t i c l e b o a r d m a n u f a c t u r e . The a u t h o r r e p o r t s t h a t F i g u r e 1-20. The S t r u c t u r e of 4 , 4 ' - D i p h e n y l m e t h a n e D i i s o c y a n a t e e x c e l l e n t r e s u l t s a r e o b t a i n e d w i t h e i t h e r a r e s o r c i n o l i c o r p h l o r o g l u c i n o l i c t y p e o f t a n n i n . The u n m o d i f i e d t a n n i n a l o n g w i t h some p a r a f o r m a l d e h y d e i s s p r a y e d as a d i l u t e s o l u t i o n o n t o t h e w a f e r s or c h i p s f i r s t , f o l l o w e d by t h e s e p a r a t e a p p l i c a t i o n of MDI p r e f e r a b l y i n a f o l l o w i n g i n - l i n e b l e n d e r ( 6 5 ) . In t h i s t y p e of s y s t e m i t i s t h o u g h t t h e s u g a r s and gums n o r m a l l y f o u n d i n p i n e e x t r a c t s would c o n t r i b u t e t o t h e s t r e n g t h of t h e g l u e l i n e by r e a c t i n g w i t h t h e MDI t o form u r e t h a n e s , t h u s i n c r e a s i n g t h e amount of c r o s s l i n k i n g p r e s e n t . The p r o b l e m w i t h t h e use of MDI as a f o r t i f i e r i s i t s h i g h c o s t . I t i s a p p r o x i m a t e l y 50% more e x p e n s i v e t h a n a PF r e s i n ( 6 0 ) . New Z e a l a n d F o r e s t P r o d u c t s L i m i t e d (NZFP) has r e c e n t l y s t a r t e d p r o d u c i n g p lywood and p a r t i c l e b o a r d bonded w i t h a d h e s i v e s b a s e d on r a d i a t a p i n e bark e x t r a c t s ( 9 8 ) . The l a r g e s c a l e e x t r a c t i o n p l a n t c o m p l e t e d i n 1981 (22 t o n n e s / d a y ) was t h e ^ r e s u l t of an a d h e s i v e d e v e l o p m e n t program s t a r t e d i n 1955. T h e i r c o m m e r c i a l plywood a d h e s i v e i s a f o r t i f i e d one, w i t h a r a t i o of t a n n i n t o PF of a p p r o x i m a t e l y 2.5 t o 1. The p a r t i c l e b o a r d a d h e s i v e i s u n f o r t i f i e d but t h e e x t r a c t has been 45 m o d i f i e d i n o r d e r t o c o n t r o l t h e v i s c o s i t y ( 9 8 ) . Th e s e a d h e s i v e s have not y e t been a c c e p t e d o u t s i d e o f New Z e a l a n d , a l t h o u g h m i l l t r i a l s w i l l soon be underway i n A u s t r a l i a ( 9 9 ) . I - E . Summary Compared t o o t h e r B r i t i s h C o l u m b i a n a t i v e t r e e s p e c i e s , t h e ba r k of w e s t e r n hemlock i s a v e r y r i c h s o u r c e of n a t u r a l p o l y p h e n o l i c s . F o r t h i s r e a s o n , w e s t e r n hemlock has been one of t h e g r o u p of t r e e s p e c i e s t h a t has been s t u d i e d w o r l d - w i d e as a p o s s i b l e s o u r c e of t r e e b a r k t a n n i n s t h a t c o u l d s u b s t i t u t e f o r th e p e t r o l e u m d e r i v e d a d h e s i v e s w i d e l y used i n t h e m a n u f a c t u r e of f o r e s t p r o d u c t s . In some s i t u a t i o n s , p a r t i c u l a r l y i n S o u t h A f r i c a w i t h w a t t l e t a n n i n s , t h e r e have been s u c c e s s f u l a p p l i c a t i o n s . The p r o b l e m s f o u n d w i t h u s i n g t a n n i n from w e s t e r n hemlock as a d h e s i v e s , and from c o n i f e r s i n g e n e r a l , a r e : (1) Low bond s t r e n g t h due t o t h e h i g h a v e r a g e m o l e c u l a r w e i g h t o f t h e b a r k t a n n i n s and r e l a t i v e l y few c r o s s l i n k i n g s i t e s . (2) O v e r l y h i g h r e a c t i v i t y w i t h f o r m a l d e h y d e , making t h e p o l y m e r i z a t i o n r e a c t i o n s r a t h e r d i f f i c u l t t o c o n t r o l and r e s u l t i n g i n a s h o r t a d h e s i v e p o t - l i f e . (3) V a r i a b l e b a r k q u a l i t y , r e s u l t i n g i n v a r i a b l e bond s t r e n g t h f o r a c o n i f e r - t a n n i n b a s e d a d h e s i v e . F o r w e s t e r n hemlock i n p a r t i c u l a r , t h e bond q u a l i t y seems t o depend t o on t h e age and p a s t h i s t o r y o f t h e b a r k . 46 Some a p p r o a c h e s t h a t have been u s e d t o t r y and s o l v e t h e s e p r o b l e m s a r e : ( 1 ) U l t r a f i l t r a t i o n t o i s o l a t e t h e optimum m o l e c u l a r w e i g h t range o f t h e t a n n i n s . (2) Breakdown of t h e t a n n i n p o l y m e r i n t o s u l p h i t e d l o w e r m o l e c u l a r w e i g h t o l i g o m e r s and monomers. (3) S p e c i a l t a n n i n i s o l a t i o n and a d h e s i v e f o r m u l a t i o n t e c h n i q u e s s u c h as slow f o r m a l d e h y d e - r e l e a s e a g e n t s , s p e c i a l i z e d e x t r a c t i o n t e c h n i q u e s and h i g h p r e s s -t e m p e r a t u r e s . T hese t e c h n i q u e s have not been e n t i r e l y s u c c e s s f u l . At t h e p r e s e n t t i m e , t h e o n l y c o m m e r c i a l a p p l i c a t i o n of c o n i f e r b a r k t a n n i n s as wood a d h e s i v e s i s i n New Z e a l a n d u s i n g r a d i a t a p i n e . 47 CHAPTER I I . THE TIME-TEMPERATURE DEPENDENCE OF THE YIELD OF CATECHOL FROM CATECHIN AND WESTERN HEMLOCK BARK POLYPHENOLS In t h i s t h e s i s , t h e a p p r o a c h t a k e n t o t h e p r o b l e m of how t o use c o n i f e r t a n n i n s as a d h e s i v e s was t o b r e a k down t h e t a n n i n i n t o s i m p l e r p h e n o l i c m o l e c u l e s t h a t would be e a s i e r t o u t i l i z e a s an a d h e s i v e b a s e . A r e a c t i o n was i n v e s t i g a t e d t h a t c l e a v e s c a t e c h i n (a model compound f o r c o n i f e r t a n n i n s ) i n t o c a t e c h o l and o t h e r r e l a t i v e l y s i m p l e compounds, t h e n a t u r e of which depends on t h e s o u r c e of t h e t a n n i n . The a d h e s i v e p r o p e r t i e s of c a t e c h o l and some of t h e o t h e r s i m p l e p h e n o l i c s t h a t can be formed, a r e w e l l known as monomers i n P F - t y p e r e s i n s . I f t h e s e p r o d u c t s were i s o l a t e d from t h e p r o d u c t m i x t u r e i n s u f f i c i e n t q u a n t i t i e s t h e y c o u l d be u s e d t o make e x c e l l e n t a d h e s i v e s . C a t e c h o l can be p r o d u c e d from s i m p l e f l a v a n o i d s s u c h as c a t e c h i n , or from bark p o l y p h e n o l s by a c l e a v a g e r e a c t i o n u s i n g a 30% s o l u t i o n of ( N H „ ) 2 S 0 3 i n c o n c e n t r a t e d N H „ O H ( t h i s r e a g e n t and s o l v e n t i s a b b r e v i a t e d t o ( N H „ ) 2 S O 3 / N H 3 ) . I n v e s t i g a t i n g t h e mechanism of t h i s r e a c t i o n and e v a l u a t i n g t h e f e a s i b i l i t y of u s i n g t h e p r o d u c t m i x t u r e as an a d h e s i v e i s t h e b a s i s of t h i s t h e s i s . In o r d e r t o o b t a i n i n f o r m a t i o n on t h e mechanism of t h i s r e a c t i o n and a l s o t o d e v e l o p r e a c t i o n c o n d i t i o n s t h a t would g i v e t h e maximum y i e l d of c a t e c h o l , i t was n e c e s s a r y t o f i r s t f i n d or d e v e l o p an a s s a y method f o r t h i s compound. Two d i f f e r e n t a s s a y p r o c e d u r e s have been d e s c r i b e d i n t h e l i t e r a t u r e . The t r a d i t i o n a l c o l o r i m e t r i c method i s t o r e a c t t h e c a t e c h o l w i t h e t h y l amine m o l y b d a t e i n m e t h a n o l , t h e n r e a d t h e s p e c t r o p h o t o m e t r i c a b s o r b a n c e of t h e r e s u l t i n g complex a t 435 mu 48 ( 1 0 0 ) . The r e a d i n g can t h e n be r e l a t e d t o c a t e c h o l c o n c e n t r a t i o n by a s t a n d a r d c u r v e . A n o t h e r method u s e s a gas c h r o m a t o g r a p h t o o b t a i n a r e a s f o r t h e peaks c o r r e s p o n d i n g t o c a t e c h o l and an i n t e r n a l s t a n d a r d . A known amount of t h e s t a n d a r d i s added t o t h e c a t e c h o l s o l u t i o n , t h e m i x t u r e i s t h e n a c e t y l a t e d , and the r e s u l t i n g a c e t a t e s a n a l y s e d u s i n g an a p p r o p r i a t e l y e q u i p p e d gas c h r o m a t o g r a p h ( 1 0 1 ) . The r a t i o of t h e c a t e c h o l and s t a n d a r d peak a r e a s can be r e l a t e d t o a w e i g h t r a t i o o b t a i n e d from a c a l i b r a t i o n c u r v e . I n i t i a l l y , t h e l a t t e r method was u s e d i n t h i s s t u d y . However, i t was soon a p p a r e n t t h a t t h e p r o c e d u r e was not s u i t a b l e f o r r a p i d a n a l y s i s of l a r g e numbers of s a m p l e s , and a s e c o n d GC-based a s s a y p r o c e d u r e was d e v e l o p e d . A d e s c r i p t i o n of t h e d e v e l o p m e n t o f t h e s e p r o c e d u r e s and t h e r e s u l t s o b t a i n e d w i t h them i s g i v e n below. (1) GC A s s a y U s i n g A c e t y l a t e d C a t e c h o l The i n t e r n a l s t a n d a r d u s e d by o t h e r w o r k e r s was o - c r e s o l ( 2 - m e t h y l p h e n o l ) . I t was d e c i d e d not t o use t h i s compound, m a i n l y b e c a u s e i t i s q u i t e v o l a t i l e and h a r d t o p u r i f y . I t s low m e l t i n g p o i n t (30° C) makes i t d i f f i c u l t t o r e c r y s t a l l i z e , and p u r i f i c a t i o n by d i s t i l l a t i o n g i v e s a c o l o r e d p r o d u c t even under vacuum due t o t h e h i g h t e m p e r a t u r e r e q u i r e d . I n s t e a d , p h l o r o g l u c i n o l was c h o s e n . T h i s p h e n o l i s r e a d i l y r e c r y s t a l l i z e d from m e t h a n o l . The t r i a c e t a t e i s e a s i l y formed 49 u s i n g a c e t i c a n h y d r i d e / p y r i d i n e and has a r e t e n t i o n t i m e c l o s e t o c a t e c h o l d i a c e t a t e . One d i s a d v a n t a g e t o u s i n g p h l o r o g l u c i n o l as a s t a n d a r d i s t h a t i t i s u n s t a b l e i n s o l u t i o n . A f t e r a b o u t one week, t h e s o l u t i o n t u r n s y e l l o w , and a f r e s h s o l u t i o n has t o be made. The b a s i c a s s a y p r o c e d u r e was t h a t a f t e r a d d i t i o n of t h e i n t e r n a l s t a n d a r d t o t h e r e a c t i o n p r o d u c t s o l u t i o n , t h e c a t e c h o l and p h l o r o g l u c i n o l were i s o l a t e d by s o l v e n t e x t r a c t i o n , a c e t y l a t e d and t h e n a n a l y s e d by gas c h r o m a t o g r a p h y . In t h e r e s u l t i n g chromatogram, the p eaks had r e a s o n a b l e r e t e n t i o n t i m e s ( c a t e c h o l - d i a c e t a t e - 250 s, p h l o r o g l u c i n o l t r i a c e t a t e - 400 s) w i t h a f l a t b a s e l i n e ( a t a column t e m p e r a t u r e of 225° C ) . A f i n a l s t e p t o 290° C was r e q u i r e d t o c l e a n compounds of low v o l a t i l i t y from t h e column ( F i g u r e 11 — 1 ) . The r a t i o of t h e c a t e c h o l d i a c e t a t e and p h l o r o g l u c i n o l t r i a c e t a t e peak a r e a s were t h e n compared t o a c a l i b r a t i o n c u r v e of known w e i g h t r a t i o s ( c a t e c h o l / p h l o r o g l u c i n o l ) , v e r s u s t h e same a r e a r a t i o s o b t a i n e d from i n t e g r a t i o n of t h e c h r o m a t o g r a p h . The r e l a t i o n s h i p between t h e a r e a and w e i g h t r a t i o s were d e t e r m i n e d by m i x i n g a p p r o p r i a t e volumes of c a t e c h o l d i a c e t a t e and p h l o r o g l u c i n o l t r i a c e t a t e s t a n d a r d s o l u t i o n s , and t h e n c a l c u l a t i n g t h e peak a r e a r a t i o s o b t a i n e d from GC a n a l y s i s . The r a t i o of the peak a r e a s were t h e n p l o t t e d a g a i n s t t h e known w e i g h t r a t i o ( F i g u r e 11-2) . I t was soon a p p a r e n t t h a t t h i s p r o c e d u r e was t o o c o m p l i c a t e d and t i m e - c o n s u m i n g . F o r t e n , o n e - m i l l i l i t e r s a m p l e s , t h e workup and a n a l y s i s took a b o u t t e n h o u r s . A n o t h e r 50 F i g u r e 11-1 . T y p i c a l Gas Chromatogram of A c e t y l a t e d C a t e c h o l and P h l o r o g l u c i n o l 51 A 1 1 1 1 r— 1.0 2.0 3.0 4.0 5.0 Area Ratio (Catechol/Phloroglucinol) F i g u r e I I - 2 . C a l i b r a t i o n Graph f o r A c e t y l a t e d C a t e c h o l p r o b l e m was t h a t the p h e n o l s i s o l a t e d by s o l v e n t e x t r a c t i o n of t h e r e a c t i o n s o l u t i o n had t o be r e a s o n a b l y d r y b e f o r e t h e y c o u l d be a c e t y l a t e d . T h i s meant d r y i n g under vacuum o v e r a d r y i n g a g e n t . C a t e c h o l s u b l i m e s r e a d i l y , and i f t h e r e s i d u e from t h e e v a p o r a t i o n o f the e x t r a c t i o n s o l v e n t i s l e f t under vacuum t o o l o n g , a s i g n i f i c a n t amount of c a t e c h o l may be l o s t . F o r t h e s e 52 r e a s o n s , t h i s a s s a y p r o c e d u r e u s i n g a c e t y l a t e d c a t e c h o l was u s e d o n l y u n t i l a b e t t e r a s s a y c o u l d be d e v e l o p e d . (2) A s s a y System f o r U n d e r i v a t i z e d C a t e c h o l I d e a l l y , i t would have been d e s i r a b l e t o a n a l y s e f o r c a t e c h o l w i t h o u t i s o l a t i n g or d e r i v a t i z i n g i t . A c o l o r i m e t r i c method would not be p o s s i b l e b e c a u s e t h e r e a c t i o n m i x t u r e i t s e l f i s h i g h l y c o l o r e d . N o r m a l l y , p h e n o l s a r e t o o r e a c t i v e t o be u s e d d i r e c t l y i n a GC a n a l y s i s . S e v e r e peak t a i l i n g makes r e l i a b l e i n t e g r a t i o n i m p o s s i b l e . CSP-633 p a c k i n g ( C h r o m a t o g r a p h i c S p e c i a l t i e s ) i s c o m p l e t e l y d e a c t i v a t e d and s p e c i f i c a l l y d e s i g n e d f o r a n a l y s i s of f r e e p h e n o l s , a l t h o u g h t h e m a n u f a c t u r e r s had n e v e r u s e d p o l y h y d r o x y p h e n o l s s u c h as c a t e c h o l on t h i s l i q u i d phase ( 1 0 2 ) . U s i n g t h i s p a c k i n g , t h e c a t e c h o l d i d n o t need t o be i s o l a t e d from t h e r e a c t i o n m i x t u r e and d e r i v a t i z e d , c o n s i d e r a b l y s h o r t e n i n g the a s s a y p r o c e d u r e . The f i r s t t h i n g t r i e d upon o b t a i n i n g t h e CSP-633, was t o pack a 48 i n . s t a i n l e s s s t e e l column w i t h i t . When a s o l u t i o n of c a t e c h o l was i n j e c t e d , t h e r e s u l t i n g peak showed s e v e r e t a i l i n g . T h i s was a t t r i b u t e d t o i n t e r a c t i o n between th e c a t e c h o l and t h e m e t a l column. T h e r e were no a n a l y t i c a l g l a s s c olumns a v a i l a b l e f o r t h e gas c h r o m a t o g r a p h b e i n g u s e d , so a n o t h e r column u s i n g 1/8 i n . O.D. t e f l o n t u b i n g was made. In o r d e r t o a v o i d t h e m e t a l i n t h e i n j e c t i o n p o r t , t h i s column was d e s i g n e d f o r on-column i n j e c t i o n w i t h t h e sample i n j e c t e d 53 d i r e c t l y i n t o t h e column ( F i g u r e 1 1 - 3 ) . T h i s s y s t e m gave chromatograms w i t h s y m m e t r i c a l , s h a r p peaks and c o n s i s t e n t r e t e n t i o n t i m e s when u s i n g c a t e c h o l / w a t e r s o l u t i o n s . However, when s a m p l e s of t h e r e a c t i o n m i x t u r e were a n a l y s e d , t h e column seemed t o d e g r a d e a f t e r o n l y a few i n j e c t i o n s . The n o n - v o l a t i l e components o f t h e r e a c t i o n m i x t u r e ( i n c l u d i n g ( N H „ ) 2 S 0 3 ) t h a t a r e d e p o s i t e d on t h e w a l l s of t h e column a f t e r sample i n j e c t i o n were b l o c k i n g t h e gas f l o w w i t h i n t h e s m a l l I.D. t u b i n g (1/16 i n . ) . The s o l u t i o n t o t h i s p r o b l e m was t o go t o a 1/4 i n . O.D. g l a s s p r e p a r a t i v e column 24 i n . l o n g , a l s o d e s i g n e d f o r on-column i n j e c t i o n . O c c a s i o n a l c l e a n i n g can be done by r e m o v i n g the column and w i p i n g out t h e i n t e r i o r of t h e f i r s t c o u p l e of i n c h e s of t h e t u b i n g u s i n g a damp t i s s u e . I n i t i a l l y , t h i s s y s t e m worked w e l l and a s t a n d a r d i z a t i o n c u r v e was d e t e r m i n e d u s i n g water s o l u t i o n s c o n t a i n i n g known amounts o f c a t e c h o l and o - c r e s o l ( F i g u r e 1 1-4 ) . P h l o r o g l u c i n o l was not u s e d as t h e s t a n d a r d b e c a u s e of i t s r e l a t i v e l y h i g h r e a c t i v i t y . I t may i n t e r a c t w i t h some components of t h e r e a c t i o n m i x t u r e and l o w e r i t s e f f e c t i v e c o n c e n t r a t i o n . In t h i s c a s e i t was f e l t t h a t t h e more s t a b l e o - c r e s o l was a b e t t e r s t a n d a r d . However, a d i f f e r e n t p r o b l e m d e v e l o p e d a f t e r e x t e n d e d use o f t h e column f o r a n a l y s i s of t h e r e a c t i o n m i x t u r e s . A f t e r 10 t o 15 i n j e c t i o n s , -the c a t e c h o l peak s t a r t e d t o b r o a d e n and i t s r e t e n t i o n t i m e g o t l o n g e r . I n i t i a l l y , i t was t h o u g h t t h a t t h i s was due t o w ater b e i n g a d s o r b e d t o t h e column, as r e p e a t e d i n j e c t i o n s of c a t e c h o l / d r y e t h e r s o l u t i o n s d i d not p r o d u c e t h i s e f f e c t . E x t e n s i v e h e a t i n g (200° C f o r 12 h r s . ) and r e p e a t e d 54 Injection Fort Syringe Septum C o l u m n ^ Column P a c k i n g Regular Injection L On-Column I n j e c t i o n F i g u r e 11- 3 . GC I n j e c t i o n Systems 55 Weight Ratio (Catechol/o-Cresol) F i g u r e I I - 4 . C a l i b r a t i o n G r a p h f o r U n d e r i v a t i z e d C a t e c h o l i n j e c t i o n s o f d r y e t h e r and e t h a n o l d i d not r e s t o r e a f f e c t e d c o l u m n s , i n d i c a t i n g t h a t water a d s o r p t i o n was not the p r o b l e m . I t had been n o t i c e d p r e v i o u s l y t h a t water i n j e c t e d on a u s e d CSP-633 column p r o d u c e s a , l a r g e peak. T h i s was u n e x p e c t e d as t h e f l a m e i o n i z a t i o n d e t e c t o r of t h i s c h r o m a t o g r a p h i s n o r m a l l y i n s e n s i t i v e t o w a t e r . I t a p p e a r e d t h a t t h e water was w a s h i n g out m a t e r i a l t h a t had been a d s o r b e d t o t h e p a c k i n g w h i c h gave t h e a p p a r e n t water peak. I t was t h o u g h t t h a t whatever was b e i n g washed out c o u l d a l s o be t h e c a u s e of t h e peak t a i l i n g o b s e r v e d . I n j e c t i o n of water i n t o an a f f e c t e d column u n t i l t h e 56 r e s u l t i n g peak was v e r y s m a l l and not d e c r e a s i n g i n s i z e , f o l l o w e d by i n j e c t i o n of a r e a c t i o n m i x t u r e sample, showed t h a t t h e p a c k i n g had been r e s t o r e d t o i t s o r i g i n a l e f f e c t i v e n e s s . The a d s o r b e d m a t e r i a l was t h e c a u s e of t h e peak b r o a d e n i n g . The b a s i c a s s a y p r o c e d u r e f o r u n d e r i v a t i z e d c a t e c h o l was t o add an i n t e r n a l s t a n d a r d t o t h e c r u d e r e a c t i o n m i x t u r e , i n j e c t a sample i n t o t h e GC, and t h e n a n a l y s e t h e r e s u l t i n g GC t r a c e u s i n g a c a l i b r a t i o n g r a p h . T h e r e i s no need t o i s o l a t e o r d e r i v a t i z e t h e c a t e c h o l , s a v i n g about e i g h t h o u r s of work per t e n s a m p l e s . A r e p r e s e n t a t i v e chromatogram i s shown i n F i g u r e 1 1 - 5 . (3) O p t i m i z a t i o n o f C a t e c h o l Y i e l d f r o m C a t e c h i n The y i e l d of c a t e c h o l from c a t e c h i n u s i n g ( N H „ ) 2 S 0 3 / N H 3 , was i n v e s t i g a t e d a t a number of t e m p e r a t u r e s f o r v a r i o u s r e a c t i o n t i m e s . F i g u r e I I - 6 summarizes t h e r e s u l t s . E a c h p o i n t i s t h e a v e r a g e o f two r e s u l t s o b t a i n e d from s e p a r a t e s o l u t i o n s , s u b j e c t e d t o t h e same c o n d i t i o n s of r e a c t i o n t e m p e r a t u r e and t i m e . The b e s t m o l a r y i e l d o f 30% was o b t a i n e d a t 175° C w i t h a r e a c t i o n t i m e of 2 h o u r s . A c t u a l i s o l a t i o n of t h e c a t e c h o l from a l a r g e r s c a l e r e a c t i o n ( u s i n g t h e same c o n d i t i o n s ) gave a y i e l d of 35% of p u r e r e c r y s t a l l i z e d c a t e c h o l . The h i g h e r y i e l d i n t h i s c a s e may have been due t o a h i g h e r c o n c e n t r a t i o n of c a t e c h i n i n t h e r e a c t i o n s o l u t i o n - 1 g c a t e c h i n p e r 10 ml r e a c t i o n s o l u t i o n v e r s u s 0.25 g c a t e c h i n per 10 ml i n t h e s m a l l 57 F i g u r e 11-5. T y p i c a l Gas Chromatogram of C a t e c h o l and o - C r e s o l 58 40- • u 3 30. > 20 10- -1 2 5 ° c Time(hrs.) 50-r 40- -o 3 3o4-^ 20- • io- • 1 5 0 ° c A .A A- . A — A i i Time(hrs.) 1 f 50+ 40- • 3 3 0 + 2 > 20 175 ° c A Time(hrs.) 50-r 40- • o 3 3 0 0) 10- -A 200 ° c • / >- 20- • / A -i 1-Time(hrs.) F i g u r e I I - 6 . M o l a r Y i e l d s of C a t e c h o l from C a t e c h i n a t 125° C, 150° C, 175° C and 200° C f o r V a r i o u s R e a c t i o n Times U s i n g ( N H a ) 2 S O 3 / N H 3 . s c a l e r e a c t i o n s of F i g u r e I I - 6 . The y i e l d of c a t e c h o l from s o l u t i o n s of c a t e c h i n i n 30% ( N H „ ) 2 S 0 3 / H 2 0 was a l s o done a t r e a c t i o n t e m p e r a t u r e s of 150° C and 175° C ( F i g u r e I I - 7 ) . The maximum y i e l d s i n t h e s e e x p e r i m e n t s were l e s s t h a n when c o n c e n t r a t e d N H„0H was used as th e r e a c t i o n s o l v e n t , and a l s o o c c u r e d a t l o n g e r r e a c t i o n t i m e s . TLC a n a l y s i s of t h e s o l u t i o n s showed fewer r e a c t i o n p r o d u c t s i n 59 404-o 3 30+ .2 > 20+ 10' -150 °C Time(hrs.) 50 T 40- • U 3 30. 0) > 20 I0- -175 °C A-.A- "A A Time (hrs.) F i g u r e I I - 7 . M o l a r Y i e l d s of C a t e c h o l From C a t e c h i n a t 150° C and 175° C f o r V a r i o u s R e a c t i o n Times U s i n g ( N H „ ) 2 S 0 3 / H 2 0 . t h e ammoniacal s o l v e n t , so t h e s t a n d a r d c o n d i t i o n s c h o s e n f o r i n v e s t i g a t i n g t h e n a t u r e of t h e c a t e c h i n r e a c t i o n u s e d a c o n c e n t r a t e d ammonia s o l u t i o n c o n t a i n i n g 30% ( N H „ ) 2 S 0 3 a t 175° C f o r 2 h o u r s . (4) O p t i m i z a t i o n o f C a t e c h o l Y i e l d from Bark E x t r a c t A 95% e t h a n o l e x t r a c t of f r e s h l y c o l l e c t e d b a r k was u s e d i n t h i s s e c t i o n . The y i e l d of e x t r a c t was 26.5% ( d r y w e i g h t s , w/w). C a t e c h o l was p r o d u c e d a t d i f f e r e n t t e m p e r a t u r e s f o r v a r i o u s r e a c t i o n t i m e s as f o r t h e e x p e r i m e n t s w i t h c a t e c h i n . The y i e l d s of c a t e c h o l from bark e x t r a c t a t r e a c t i o n t e m p e r a t u r e s of 150° C, 175° C and 200° C a r e shown i n F i g u r e 11-8. The y i e l d s i n t h i s c a s e a r e p e r c e n t a g e s of t h e w e i g h t of 60 3- • Yield 2. (Pet.) 4- -3- • Yield ZH (Pet.) 4 ^ 175°C H H H h Time(hrs.) 150°C A 1 1 1 1 r-2 4 6 8 Time(hrs.) 200°C 10 12 14 16 Yield 2X (Pet.) _l 1 1 (-2 3 4 5 Time(hrs.) F i g u r e I I - 8 . Weight P e r c e n t Y i e l d s of C a t e c h o l From W e s t e r n Hemlock B a r k - E t h a n o l E x t r a c t a t 150° C, 175° C and 200° C f o r V a r i o u s R e a c t i o n Times U s i n g ( N H „ ) 2 S 0 3 / N H 3 61 c a t e c h o l p r o d u c e d from a known w e i g h t of e x t r a c t . A maximum y i e l d o f a b o u t 3% was o b s e r v e d a t 175° C, when a r e a c t i o n time of 4 h o u r s was u s e d , and a t 150° C w i t h 10 h o u r s r e a c t i o n t i m e . The h i g h e r t e m p e r a t u r e c o n d i t i o n s were u s e d where p o s s i b l e i n f u r t h e r work w i t h bark p o l y p h e n o l s b e c a u s e of t h e s h o r t e r , more c o n v e n i e n t r e a c t i o n t i m e . (5) C a t e c h o l Y i e l d f r o m S e q u e n t i a l Bark E x t r a c t s Two s e q u e n t i a l s o l v e n t e x t r a c t i o n s of w e s t e r n hemlock bark were done. The f i r s t f o l l o w e d t h e p r o c e d u r e of F r a s e r and Swan ( 3 2 ) , w i t h s e q u e n t i a l e x t r a c t i o n s o f b e n z e n e / e t h a n o l , e t h a n o l , water and 1% NaOH. A p o r t i o n of e a c h e x t r a c t was r e a c t e d w i t h ( N H « ) 2 S O 3 / N H 3 a t 175° C f o r 4 h o u r s , and t h e amount of c a t e c h o l p r o d u c e d was measured. A g r a p h of y i e l d of e x t r a c t , and how much c a t e c h o l i s o b t a i n e d from a p a r t i c u l a r e x t r a c t v e r s u s e x t r a c t t y p e , i s shown i n F i g u r e 11-9. The maximum c a t e c h o l y i e l d of 3.3% was o b t a i n e d from t h e e t h a n o l e x t r a c t i o n . T h i s r e s u l t would be e x p e c t e d from a n a l y s i s of t h e components of e a c h e x t r a c t t y p e . The b e n z e n e / e t h a n o l e x t r a c t c o n t a i n e d f a t s , waxes and n o n - f l a v a n o i d p h e n o l i c s t h a t c o u l d n o t decompose t o c a t e c h o l but w h i c h c o n t r i b u t e t o t h e w e i g h t o f t h e e x t r a c t . S i m p l e f l a v a n o i d s and b i f l a v a n o i d s a r e e x t r a c t e d w i t h e t h a n o l and would be e x p e c t e d t o r e a c t t o g i v e c a t e c h o l i n t h e b e s t y i e l d , s i n c e a c c e s s i b i l i t y and s t e r e o c h e m i s t r y p r o b l e m s would be m i n i m i z e d . H i g h e r m o l e c u l a r 62 Benzene/ EtOH Water Base EtOH Extraction Solvent F i g u r e I I - 9 . Y i e l d of E x t r a c t s and C a t e c h o l from F o u r S e q u e n t i a l E x t r a c t i o n s of W e s t e r n Hemlock B a r k . w e i g h t p o l y f l a v a n o i d s and some c a r b o h y d r a t e s would be c o n t a i n e d i n t h e water e x t r a c t and a lo w e r c a t e c h o l y i e l d would be e x p e c t e d . To f i n d out whether t h e p h e n o l i c a c i d s of t h e base e x t r a c t would r e a c t t o form c a t e c h o l , c a t e c h i n i c a c i d ( F i g u r e I -9) was p r e p a r e d and t e s t e d . I t was fo u n d t h a t t h i s compound does not decompose t o c a t e c h o l when t r e a t e d w i t h ( N H „ ) 2 S O 3 / N H 3 a t 175° C. T h i s p r o b a b l y e x p l a i n s why s u c h a low y i e l d of c a t e c h o l was o b t a i n e d from t h e base e x t r a c t . A s e c o n d s e r i e s of e x t r a c t i o n s u s e d a sequence of s o l v e n t s 6 3 i n o r d e r of i n c r e a s i n g d i p o l e moment. The s o l v e n t s u s e d were p e t r o l e u m e t h e r , benzene, d i e t h y l e t h e r , a c e t o n e , e t h a n o l , and w a t e r . I t was hoped t h a t t h e i n c r e a s e d f r a c t i o n a t i o n would r e s u l t i n an e x t r a c t w i t h a h i g h e r y i e l d of c a t e c h o l t han t h e e t h a n o l e x t r a c t o f t h e p r e v i o u s s e r i e s . The components of t h i s f r a c t i o n c o u l d t h e n be c h a r a c t e r i z e d t o g i v e b e t t e r i n f o r m a t i o n on t h e n a t u r e of t h e bark compounds t h a t w i l l r e a c t t o form c a t e c h o l . In f a c t , t h e o p p o s i t e o c c u r r e d . F i g u r e 11-10 shows t h e e x t r a c t and r e a c t i o n y i e l d s of t h i s e x p e r i m e n t . A lower F i g u r e 11-10. Y i e l d of E x t r a c t s and C a t e c h o l from S i x S e q u e n t i a l E x t r a c t i o n s o f W e s t e r n Hemlock Bark maximum y i e l d of 2% was o b s e r v e d f o r t h e a c e t o n e e x t r a c t . T h i s 64 was p r o b a b l y due t o t h e f a c t t h a t b a r k e x t r a c t s , and i n p a r t i c u l a r t h o s e o f w e s t e r n hemlock, a r e p r o n e t o a g i n g ( 3 2 ) . T h e r e was a gap of about 6 weeks between t h e two e x p e r i m e n t s , and a l t h o u g h t h e b a r k was s t o r e d a t 0° C, some p o l y m e r i z a t i o n of t h e low m o l e c u l a r w e i g h t p o l y f l a v a n o i d s may have o c c u r r e d . T h e s e a r e t h e components t h a t a r e p r o b a b l y d e c o m p o s i n g t o form c a t e c h o l i n t h e d e g r a d a t i o n r e a c t i o n , so a s m a l l change i n t h e a v e r a g e m o l e c u l a r w e i g h t of t h i s f r a c t i o n may have a l a r g e e f f e c t on t h e i r r e a c t i v i t y t o ( N H „ ) 2 S 0 3 . A n o t h e r f a c t o r t h a t may be i m p o r t a n t i s t h e e x t r a c t i o n t i m e . In t h e f i r s t s e r i e s , t h e b e n z e n e / e t h a n o l e x t r a c t i o n l a s t e d f o r o v e r 24 h o u r s , w h i l e th e e t h a n o l e x t r a c t i o n i n t h i s c a s e p r o c e e d e d f o r 12 h o u r s . D u r i n g t h i s t i m e t h e e x t r a c t was b e i n g h e a t e d a t t h e r e f l u x t e m p e r a t u r e of t h e s o l v e n t , p o s s i b l y r e s u l t i n g i n an i n c r e a s e d r a t e of p o l y m e r i z a t i o n . T h i s c o u l d a c c o u n t f o r t h e r a t h e r low y i e l d of c a t e c h o l from t h e b e n z e n e / e t h a n o l e x t r a c t . In o r d e r t o d e t e r m i n e t h e maximum p o s s i b l e y i e l d o f c a t e c h o l from w e s t e r n hemlock bark u s i n g t h e r e a c t i o n , t e n grams of f r e s h l y c o l l e c t e d , f i n e l y g r o u n d whole bark was t e s t e d w i t h 30% ( N H „ ) 2 S 0 3 / N H 3 a t 175° C f o r 4 h o u r s . The aqueous ammonia s o l u t i o n i t s e l f a c t e d as t h e e x t r a c t i o n medium, t h u s a v o i d i n g any d e g r a d a t i o n t h a t might o c c u r d u r i n g t h e p r o c e s s of s o l v e n t e x t r a c t i o n . A n a l y s i s o f t h e p r o d u c t s showed t h a t 98 mg of c a t e c h o l had been formed. On a whole b a r k b a s i s , t h i s i s a y i e l d o f 1.1%. I f i t i s assumed t h a t 25% o f t h e bark i s composed of f l a v a n o i d s and p o l y f l a v a n o i d s a c c e s s i b l e t o t h i s 65 r e a c t i o n , t h e w e i g h t y i e l d was 4.5% and t h e m o l a r y i e l d was abo u t 13% ( b a s e d on t h i s p o r t i o n b e i n g a l l c a t e c h o l - c o n t a i n i n g m o n o f l a v a n o i d s ) . (6) Summary A q u i c k GC-based a s s a y p r o c e d u r e f o r c a t e c h o l was d e v e l o p e d u s i n g a d e a c t i v a t e d p a c k i n g and an i n t e r n a l s t a n d a r d . W i t h t h i s method, t h e optimum r e a g e n t and c o n d i t i o n s f o r p r o d u c t i o n of c a t e c h o l from c a t e c h i n were d e t e r m i n e d t o be a s o l u t i o n of 30% ammonium s u l p h i t e i n c o n c e n t r a t e d ammonium h y d r o x i d e h e a t e d t o 175° C f o r 2 h o u r s . Under t h e s e c o n d i t i o n s , a 35% m o l a r y i e l d o f c a t e c h o l was o b t a i n e d . D e t e r m i n i n g the y i e l d of c a t e c h o l from s e q u e n t i a l e x t r a c t s of w e s t e r n hemlock bark showed t h a t t h e b e s t r e s u l t s c o u l d be o b t a i n e d from an e x t r a c t c o n t a i n i n g t h e h i g h e s t c o n c e n t r a t i o n of low m o l e c u l a r w e i g h t p o l y p h e n o l s . The e x t r a c t i o n t i m e and f r e s h n e s s of t h e bark were a l s o f o u n d t o be i m p o r t a n t f a c t o r s i n o p t i m i z i n g t h e c a t e c h o l y i e l d . On a whole b a r k b a s i s , t h e b e s t y i e l d of c a t e c h o l was 1.1%. T h i s c o r r e s p o n d s t o a w e i g h t y i e l d of 4.5% and a m o l a r y i e l d of 13%, i f i t i s assumed t h a t 25% of t h e b a r k i s composed of f l a v a n o i d s and p o l y f l a v a n o i d s a c c e s s i b l e t o t h i s r e a c t i o n . 6 6 CHAPTER I I I . INVESTIGATION OF THE REACTION BETWEEN CATECHIN AND ( N H « ) 2 S 0 3 IN CONCENTRATED NH„OH The d e t e r m i n a t i o n of t h e mechanism of t h e r e a c t i o n t h a t c l e a v e s c a t e c h i n i n t o c a t e c h o l and some o t h e r p r o d u c t s i s f u n d a m e n t a l t o t h e r e s e a r c h p r o b l e m i n v e s t i g a t e d i n t h i s t h e s i s . The s t e p s u s e d t o a c c o m p l i s h t h i s a i m were: (1) C h a r a c t e r i z a t i o n of an i n t e r m e d i a t e compound i n t h e c l e a v a g e r e a c t i o n and i d e n t i f i c a t i o n of t h e " o t h e r p r o d u c t s " t h a t c o u l d have been d e r i v e d from t h e A- and C-r i n g p o r t i o n s of t h e c a t e c h i n m o l e c u l e . I d e n t i f i c a t i o n of t h e f o r m e r would p r o v i d e a d e f i n i t e i n t e r m e d i a t e s t r u c t u r e upon w h i c h f u r t h e r p r o p o s e d m o d i f i c a t i o n s c o u l d be b a s e d . A knowledge of t h e c o - p r o d u c t s would show how t h e r e s t of t h e c a t e c h i n m o l e c u l e has been a l t e r e d by t h e c l e a v a g e of t h e B - r i n g and s h o u l d p r o v i d e v a l u a b l e c l u e s t o t h e mechanism. (2) O b s e r v a t i o n of how compounds r e l a t e d t o c a t e c h i n r e a c t under t h e same c o n d i t i o n s as t h e c a t e c h i n r e a c t i o n , by i d e n t i f i c a t i o n of t h e i r r e a c t i o n p r o d u c t s . S i m p l e compounds r e l a t e d t o t h e i n d i v i d u a l c a t e c h i n r i n g s or t h e e n t i r e m o l e c u l e were i n v e s t i g a t e d t o see what changes t o t h e A- and C- r i n g s s h o u l d be e x p e c t e d d u r i n g t h e c a t e c h i n c l e a v a g e . (3) Development of a mechanism c o n s i s t e n t w i t h t h e o b s e r v e d p r o d u c t s and t e s t i n g t h e p r o p o s e d r e a c t i o n mechanism by u s i n g i t t o p r e d i c t t h e r e s u l t s of a t e s t r e a c t i o n . T h i s t e s t s h o u l d show how v a l i d t h e p r o p o s e d mechanism i s . 67 A d i s c u s s i o n of t h e r e s u l t s of t h e s e e x p e r i m e n t s i s p r e s e n t e d i n t h i s c h a p t e r . I I I - A . I d e n t i f i c a t i o n of an I n t e r m e d i a t e and Some P r o d u c t s (1) 1 - ( 3 , 4 - D i h y d r o x y p h e n y l ) - 2 - h y d r o x y - 3 - ( 1 , 3 , 5 -t r i h y d r o x y p h e n y l ) p r o p a n e s u l p h o n i c Ac i d Sodium b i s u l p h i t e w i l l r e a c t w i t h c a t e c h i n i n water s o l u t i o n t o form t h e t i t l e compound. A p r o b a b l e mechanism f o r t h i s r e a c t i o n i s shown i n F i g u r e 1 1 1 — 1. R e a c t i o n c o n d i t i o n s t h a t have been d e s c r i b e d i n t h e l i t e r a t u r e a r e r e f l u x i n g s o l v e n t f o r 6 h o u r s (71) o r i n a s e a l e d c o n t a i n e r a t 170° C f o r 0 ."5 h o u r s ( 5 2 ) . I t seemed p r o b a b l e t h a t t h i s same compound would be an i n t e r m e d i a t e i n t h e r e a c t i o n of c a t e c h i n w i t h ammonium s u l p h i t e . C a t e c h i n was r e a c t e d w i t h ammonium s u l p h i t e i n ammonia s o l u t i o n f o r 24 h o u r s a t 60° C. The main p r o d u c t was i s o l a t e d and c h a r a c t e r i z e d by i t s IR and NMR s p e c t r a . The p r e s e n c e of a s u l p h o n i c a c i d g r o u p was c l e a r l y i n d i c a t e d i n t h e i n f r a r e d s p e c t r u m by s t r o n g a b s o r b a n c e s a t 1145 and 1030 cm" 1 and a weaker a b s o r b a n c e a t 650 cm" 1. A r o m a t i c r i n g s were a l s o p r o b a b l e due t o t h e c a r b o n - c a r b o n d o u b l e bond a b s o r b a n c e s a r o u n d 1615 cm" 1. C o m p a r i s o n of t h e NMR s p e c t r a of c a t e c h i n and i t s s u l p h o n a t e d r e a c t i o n p r o d u c t c l e a r l y shows t h a t t h e p y r a n C - r i n g has been opened i n t h e l a t t e r ( s e e F i g u r e 111-2). The h y d r o g e n s 68 O H S0 3 H F i g u r e 1 1 1 — 1. The R e a c t i o n of C a t e c h i n w i t h Sodium B i s u l p h i t e of t h e p h l o r o g l u c i n o l A - r i n g become e q u i v a l e n t when t h e e t h e r l i n k a g e i s b r o k e n and form a s i n g l e t due t o two p r o t o n s . T h i s s i n g l e t i s s h i f t e d d o w n f i e l d t o be s u p e r i m p o s e d o v e r t h e s i g n a l s from t h e c a t e c h o l B - r i n g a t a c h e m i c a l s h i f t of a b o u t 6 . 9 ppm. 1 The h y d r o g e n s a t C~4 (g and f ) a l s o become e s s e n t i a l l y e q u i v a l e n t when t h e p y r a n r i n g i s opened. The o b s e r v e d r e s u l t 1 A l l c h e m i c a l s h i f t s g i v e n i n t h i s t h e s i s a r e i n d e l t a u n i t s . 69 i s a d o u b l e t w i t h a r e l a t i v e i n t e n s i t y of 2, p o s i t i o n e d a t a b o u t t h e same c h e m i c a l s h i f t as t h e ddd ( d o u b l e t - d o u b l e t - d o u b l e t ) s i g n a l from t h e C-4 n o n - e q u i v a l e n t p r o t o n s i n c a t e c h i n . The p o s i t i o n of t h e d o u b l e t due t o t h e h y d r o g e n a t t a c h e d t o C-2 (d i n F i g u r e I I I - 2 ) , i s s h i f t e d u p f i e l d from 4.7 t o 3.8 upon s u b s t i t u t i o n of t h e a r o m a t i c e t h e r s u b s t i t u e n t w i t h t h e s u l p h o n a t e g r o u p . T h i s i s e x p e c t e d b e c a u s e of t h e s m a l l e r d e s h i e l d i n g e f f e c t of t h e s u l p h o n a t e . In o r d e r t o d e t e r m i n e . whether th e s u l p h o n a t e d c a t e c h i n d e s c r i b e d above c o u l d be an i n t e r m e d i a t e i n t h e h i g h t e m p e r a t u r e d e g r a d a t i o n r e a c t i o n t o c a t e c h o l , a sample of t h i s compound was t e s t e d under th e a p p r o p r i a t e r e a c t i o n c o n d i t i o n s . When the s u l p h o n a t e d c a t e c h i n was h e a t e d t o 175° C f o r two h o u r s i n a s e a l e d r e a c t i o n t u b e , t h e same p r o d u c t s were o b s e r v e d t h a t were f o u n d i n t h e d i r e c t r e a c t i o n of c a t e c h i n w i t h ammonium s u l p h i t e . T h ese e x p e r i m e n t s i n d i c a t e t h a t 1 - ( 3 , 4 - d i h y d r o x y p h e n y l ) - 2 -h y d r o x y - 3 - ( 1 , 3 , 5 - t r i h y d r o x y p h e n y l ) p r o p a n e s u l p h o n i c a c i d i s an i n t e r m e d i a t e i n t h e c l e a v a g e r e a c t i o n of c a t e c h i n t o c a t e c h o l . (2) 3 - A m i n o - 5 - h y d r o x y - 7 - q u i n o l i n e s u l p h o n i c A c i d The compound, d i s c u s s e d h e r e was i s o l a t e d from t h e m i x t u r e of p r o d u c t s p r o d u c e d a l o n g w i t h c a t e c h o l by t h e h i g h t e m p e r a t u r e c l e a v a g e of c a t e c h i n . The i n t e n s i t y of t h e s p o t on a TLC p l a t e due t o t h i s compound i n d i c a t e d i t i s p r o b a b l y t h e c a t e c h o l c o -p r o d u c t formed i n t h e h i g h e s t c o n c e n t r a t i o n . T h i s makes the 70 F i g u r e 111-2. C o m p a r i s o n of t h e NMR S p e c t r a of C a t e c h i n and i t s S u l p h o n a t e d R e a c t i o n P r o d u c t 71 c o r r e c t i d e n t i f i c a t i o n of t h i s compound v e r y i m p o r t a n t t o t h e d e t e r m i n a t i o n of t h e r e a c t i o n mechanism, as i t i s p r o b a b l y d e r i v e d f r o m a t l e a s t a p o r t i o n o f t h e A- and C - r i n g s r e m a i n i n g a f t e r c a t e c h o l i s c l e a v e d from c a t e c h i n . The way i n w h i c h t h i s p o r t i o n of t h e c a t e c h i n m o l e c u l e i s s t r u c t u r a l l y m o d i f i e d d u r i n g t h e c l e a v a g e p r o c e s s would g i v e v a l u a b l e c l u e s a s t o how t h e r e a c t i o n must have o c c u r r e d . T h i s compound can be i s o l a t e d by p a s s i n g t h e m i x t u r e of p r o d u c t s from t h e h i g h t e m p e r a t u r e r e a c t i o n of c a t e c h i n w i t h ammonium s u l p h i t e t h r o u g h a column of s t r o n g l y a c i d i c i o n exchange r e s i n . N o n - s u l p h o n a t e d compounds s u c h as c a t e c h o l p a s s t h r o u g h f r e e l y , w h i l e m a t e r i a l s w i t h a p o s i t i v e l y c h a r g e d f u n c t i o n a l g r o u p a r e r e t a i n e d on t h e column. A l p h a - a m i n o a c i d s would be s t r o n g l y h e l d t o t h e column w h i l e s p e c i e s w i t h a d e l o c a l i z e d p o s i t i v e c h a r g e would o n l y be weakly a d s o r b e d t o t h e r e s i n and e v e n t u a l l y p a s s t h r o u g h . 3-Amino-5-hydroxy-7-q u i n o l i n e s u l p h o n i c a c i d (AHQSA) i s o f the l a t t e r form, and i s t h e o n l y compound of t h i s t y p e p r e s e n t i n t h e p r o d u c t m i x t u r e i n s i g n i f i c a n t q u a n t i t i e s . By s i m p l y p a s s i n g t h e r e a c t i o n m i x t u r e t h r o u g h an i o n - e x c h a n g e column and d i s c a r d i n g t h e i n i t i a l h i g h l y c o l o r e d f r a c t i o n s , f a i r l y l a r g e q u a n t i t i e s of AHQSA can be i s o l a t e d . Y e l l o w - b r o w n c r y s t a l s c an be o b t a i n e d from r e c r y s t a l l i z a t i o n i n w a t e r . AHQSA was a n a l y s e d e x h a u s t i v e l y , ' u s i n g s t a n d a r d s p e c t r o s c o p i c t e c h n i q u e s . The IR s p e c t r a showed t h e s t r o n g c h a r a c t e r i s t i c a b s o r b a n c e s of a s u l p h o n i c a c i d a t 1190, 1040 and 640 cm" 1. The a r o m a t i c r e g i o n shows s e v e r a l a b s o r b a n c e s r a n g i n g 72 i n p o s i t i o n from 1570 t o 1640 c m - 1 , i n d i c a t i n g t h e p r e s e n c e of a number of d i f f e r e n t bonds of t h e s e t y p e s . A weak d o u b l e t a t 3450 and 3540 cm" 1 i s c o n s i s t e n t w i t h t h e p r e s e n c e of a p r i m a r y a r o m a t i c amine ( 1 0 3 ) . The . NMR s p e c t r u m i s q u i t e s i m p l e and i s shown d i a g r a m a t i c a l l y i n F i g u r e 111 — 3 a l o n g w i t h t h e s i g n a l a s s i g n m e n t s . The o n l y d e u t e r a t e d s o l v e n t i n w h i c h AHQSA i s e d b c a i I • • • II IL I I • i i i i 1 1 1 12 11 10 9 8 7 6 5 4 3 2 1 0 Chemical Shift (5) J F i g u r e 111 -3. The NMR S p e c t r u m of 3-Amino-5-hydroxy-7-q u i n o l i n e s u l p h o n i c A c i d s o l u b l e enough t o g i v e good s p e c t r a i s DMSO-d6. Most l a b i l e h y d r o g e n s w i l l exchange i n t h i s s o l v e n t and r e s u l t i n a s i n g l e b r o a d s i g n a l f o r t h e s e p r o t o n s a t a c h e m i c a l s h i f t of about 5. The f o u r s i g n a l s between 7 and 9 a r e due t o t h e c a r b o n ^ b o n d e d h y d r o g e n s on t h e a r o m a t i c r i n g s y s t e m and can be d i v i d e d i n t o 73 two p a i r s . The d o w n f i e l d s i g n a l s a r e b o t h s p l i t i n t o d o u b l e t s w i t h a s m a l l c o u p l i n g c o n s t a n t of about 1.3 Hz, w h i l e t h e o t h e r two have a n e g l i g i b l e c o u p l i n g c o n s t a n t . E x a m i n a t i o n of t h e s p e c t r a l d a t a f o r q u i n o l i n e shown i n F i g u r e 1 1 1 - 4 shows t h a t t h e 2,4 c o u p l i n g c o n s t a n t i s s u b s t a n t i a l l y l a r g e r t h a n t h e 6,8 Hydrogen Shift (5, CCiJ F i g u r e 1 1 1 - 4 . NMR S p e c t r a l Data of Q u i n o l i n e (104,105) s p l i t t i n g , so t h e d o w n f i e l d s i g n a l s i n t h e AHQSA s p e c t r u m a r e p r o b a b l y due t o t h e h y d r o g e n s a t C-2 and 4. The o t h e r two s i g n a l s would then be due t o t h e h y d r o g e n s a t C-6 and 8. E x a m i n a t i o n o f the c h e m i c a l s h i f t d a t a of q u i n o l i n e e a s i l y a l l o w s a s s i g n m e n t of t h e s i g n a l s i n each p a i r . The p r o t o n i n e a c h p a i r c l o s e s t t o t h e h e t e r o c y c l i c n i t r o g e n would be f u r t h e r d o w n f i e l d . T h i s l e a v e s o n l y t h e s i g n a l a t 11.23 u n a s s i g n e d . FrOm d a t a t h a t w i l l be p r e s e n t e d l a t e r , i t i s known t h a t AHQSA, 74 a t l e a s t i n t h e s o l i d form, i s a z w i t t e r i o n w i t h t h e h e t e r o c y c l i c n i t r o g e n b e i n g p r o t o n a t e d . T h i s h y d r o g e n seems t o be t h e s o u r c e of t h e 11.23 s i g n a l . The s i g n a l i s q u i t e b r o a d , due t o i n t e r a c t i o n w i t h t h e e l e c t r i c q u a d r o p o l e moment of t h e n i t r o g e n . In t r i f l u o r o a c e t i c a c i d s o l u t i o n s of q u i n o l i n e , a s i g n a l due t o t h e p r o t o n a t e d n i t r o g e n can a l s o be o b s e r v e d w i t h a c h e m i c a l s h i f t of 14 ppm ( 1 0 6 ) . The 1 3C-NMR s p e c t r a o f AHQSA i n DMSO c l e a r l y showed t h e n i n e c a r b o n s i g n a l s e x p e c t e d , w i t h s h i f t s r a n g i n g from 113 t o 162 ppm. No a t t e m p t was made t o a s s i g n t h e s e s i g n a l s . A UV s p e c t r a of t h i s compound showed a b s o r p t i o n maxima a t 223 and 263 mu. A d d i t i o n of a c i d o r base c a u s e d a s h i f t i n t h e a b s o r b a n c e t o h i g h e r w a v e l e n g t h s ( b a t h o c h r o m i c s h i f t ) . T h i s o b s e r v a t i o n i s c o n s i s t e n t w i t h b o t h a c i d i c arid b a s i c g r o u p s b e i n g a t t a c h e d t o t h e UV chr o m o p h o r e . Mass s p e c t r a l a n a l y s i s of AHQSA was not v e r y s u c c e s s f u l due t o t h e low v o l a t i l i t y of s u l p h o n i c a c i d s . The l a r g e s t f r a g m e n t o b s e r v e d had m/e o f 149 w i t h a base peak a t 66. I t has been r e p o r t e d t h a t tetramethylammonium s a l t s o f s u l p h o n i c a c i d s decompose upon h e a t i n g i n t h e mass s p e c t r o m e t e r t o m e t h y l s u l p h o n a t e s , w h i c h can g i v e good s p e c t r a (107, F i g u r e 1 1 1 - 5 ) . The tetramethylammonium s a l t of AHQSA was made by n e u t r a l i z i n g a s o l u t i o n of t h e a c i d w i t h t etramethylammonium h y d r o x i d e and then e v a p o r a t i n g t h e s o l v e n t . A l t h o u g h t r i m e t h y l a m i n e was o b s e r v e d i n t h e mass s p e c t r u m of t h i s d e r i v a t i v e (m/e=59), t h e l a r g e s t f r a g ment o b s e r v e d was s t i l l a t 149. An a t t e m p t t o make the m e t h y l s u l p h o n a t e d i r e c t l y , by r e a c t i o n of m e t h y l i o d i d e w i t h 75 RS0 3 N(CH 3 ) 4 R S 0 3 C H 3 + N(CH 3) 3 F i g u r e 111 — 5. D i s s o c i a t i o n of Tetramethylammonium S a l t s of S u l p h o n i c A c i d s t h e s i l v e r s a l t of t h e a c i d a c c o r d i n g t o t h e method of G i e r e r ( 1 0 8 , 1 09), was a l s o u n s u c c e s s f u l . The a c e t y l a t e d d e r i v a t i v e was i s o l a t e d and c h a r a c t e r i z e d by IR and NMR a n a l y s i s . Two d i f f e r e n t c a r b o n y l a b s o r b a n c e s were n o t e d a t 1763 and 1670 c m - 1 . T hese c o r r e s p o n d t o a c e t a t e e s t e r and amide g r o u p s r e s p e c t i v e l y . The p r e s e n c e of t h e two a c e t a t e d e r i v a t i v e s was a l s o o b v i o u s from t h e NMR s p e c t r u m , which showed two 3-hydrogen s i n g l e t s a t s h i f t s of 2.18 and 2.46 ppm. T hese s i g n a l s were due t o t h e a c e t y l a t e d amine and a l c o h o l , r e s p e c t i v e l y . The t i t r a t i o n c u r v e of AHQSA w i t h sodium h y d r o x i d e s o l u t i o n ( F i g u r e 111-6) shows two pKa's a t pH's of 3.3 and 7.5 . The f i r s t would be due t o t h e n e u t r a l i z a t i o n of t h e s u l p h o n i c a c i d g r o u p , and t h e s e c o n d t o t h e a r o m a t i c h y d r o x y l a t C-5. A m o l e c u l a r w e i g h t of 247 g/mole was c a l c u l a t e d by n o t i n g t h e e q u i v a l e n t s of base r e q u i r e d t o n e u t r a l i z e t h e known weight of a c i d t o t h e f i r s t end p o i n t . T h i s v a l u e i s r e a s o n a b l y c l o s e t o t h e t r u e m o l e c u l a r w e i g h t of 258 g/mole. C o n c l u s i v e e v i d e n c e f o r t h e i d e n t i f i c a t i o n of t h i s c a t e c h o l 76 14-13-12-11-10' 9-8-PH 7 6-5 4-3-2-V 0 pKa , = 3 3 p K a 2 =7.5 9 10 11 12 13 14 13 16 17 18 19 20 Volume (ml.) F i g u r e 111-6. T i t r a t i o n of 3-Amino-5-hydroxy-7-q u i n o l i n e s u l p h o n i c A c i d c o - p r o d u c t as 3 - a m i n o - 5 - h y d r o x y - 7 - q u i n o l i n e s u l p h o n i c a c i d came from an a n a l y s i s by x - r a y c r y s t a l l o g r a p h y . C r y s t a l s of s u f f i c i e n t s i z e and q u a l i t y p r o v e d t o be d i f f i c u l t t o grow. A number of d i f f e r e n t s o l v e n t s y s t e m s and e v a p o r a t i o n r e g i m e s were t r i e d b e f o r e s u i t a b l e c r y s t a l s were o b t a i n e d . A f r e s h l y i s o l a t e d sample of t h e compound was f i r s t r e c r y s t a l l i z e d t w i c e from m e t h a n o l / w a t e r . The p u r i f i e d m a t e r i a l was t h e n d i s s o l v e d i n t h e minimum amount of b o i l i n g w a t e r , and t h e n an e q u a l volume of c o l d water added. The c o n c e n t r a t i o n of t h e compound i n t h e w ater a t room t e m p e r a t u r e was below th e s a t u r a t i o n p o i n t , so t h e r e would have t o be some l o s s of s o l v e n t b e f o r e p r e c i p i t a t i o n 77 and c r y s t a l l i z a t i o n c o u l d o c c u r . V e r y slow e v a p o r a t i o n , was i n d u c e d by p l a c i n g t h e E r l e n m e y e r f l a s k c o n t a i n i n g t h e s o l u t i o n i n a t u n n e l o f aluminum f o i l t h a t had one end s e a l e d a r o u n d a n i t r o g e n gas i n l e t t u b e . In t h i s way, t h e c r y s t a l l i z i n g s o l u t i o n was p r o t e c t e d from l i g h t , oxygen and d u s t , w h i l e a slow r a t e of e v a p o r a t i o n was i n d u c e d by t h e f l o w o f gas o v e r t h e s o l u t i o n . Seed c r y s t a l s , s e l e c t e d u s i n g a m i c r o s c o p e from p r e v i o u s c r y s t a l l i z a t i o n a t t e m p t s , were added p e r i o d i c a l l y u n t i l enough s o l v e n t had been e v a p o r a t e d t o make t h e s o l u t i o n s a t u r a t e d , a t w h i c h p o i n t t h e s e e d c r y s t a l s would not d i s s o l v e . About two weeks a f t e r t h i s p o i n t , t h e r e s u l t i n g c r y s t a l s were i s o l a t e d and p r o v e d t o be a d e q u a t e f o r a n a l y s i s . The s t r u c t u r e o f AHQSA a l o n g w i t h t h e numbering s y s t e m and a t h r e e d i m e n s i o n a l r e p r e s e n t a t i o n i s shown i n F i g u r e I I I - 7 . The compound e x i s t s as t h e z w i t t e r i o n shown i n t h e s o l i d form w i t h one water of c r y s t a l l i z a t i o n . Bond l e n g t h s and a n g l e s a r e shown i n T a b l e s 111-1, 2, 3 and 4. E s t i m a t e d s t a n d a r d d e v i a t i o n s a r e i n p a r e n t h e s e s . (3) 3 , 5 - D i a m i n o - 7 - q u i n o l i n e s u l p h o n i c A c i d The t i t l e compound c a n be i s o l a t e d from t h e p r o d u c t m i x t u r e formed from t h e r e a c t i o n o f c a t e c h i n w i t h ammonium s u l p h i t e i n c o n c e n t r a t e d ammonia. I t was c h o s e n f o r i s o l a t i o n b a s e d on t h e i n t e n s i t y of i t s s p o t on a TLC p l a t e , i t was t h e compound 78 F i g u r e 111-7. S t r u c t u r a l and T h r e e - D i m e n s i o n a l R e p r e s e n t a t i o n s of 3 - A m i n o - 5 - h y d r o x y - 7 - q u i n o l i n e s u l p h o n i c A c i d p r e s e n t i n t h e t h i r d l a r g e s t c o n c e n t r a t i o n a f t e r c a t e c h o l and AHQSA. T h i s compound was i s o l a t e d as t h e ammonium s a l t by p r e p a r a t i v e TLC, b e c a u s e i t would not p a s s t h r o u g h an i o n exchange column. a d s o r p t i o n t o t h e column would be e x p e c t e d i f i t had a l o c a l i z e d p o s i t i v e c h a r g e s i m i l a r t o t h e p r o t o n a t e d amino g r o u p o f a 2-amino c a r b o x y l i c a c i d i n t h e z w i t t e r i o n f o r m . Proton-NMR a n a l y s i s showed t h a t t h i s compound must have a s i m i l a r c a r b o n framework and s u b s t i t u t i o n p a t t e r n t o AHQSA. 79 Bond U n c o r r . C o r r . Bond U n c o r r . C o r r . S-0(1 ) S-0(2) S-0(3) S-C(7) 1.450(2) 1.449(2) 1.447(2) 1 .779(3) 1 .461 1 .460 1 .459 1 .787 C ( 3 ) - C ( 4 ) C ( 4 ) - C ( 4 a ) C ( 4 a ) - C ( 5 ) C ( 4 a ) - C ( 8 a ) 1 . 384(4) 1.402(4) 1.428(4) 1.407(4) 1 .387 1 .405 1 .432 1.412 1 .431 1 .370 1.413 1 .367 1 .408 0 ( 4 ) - C ( 5 ) N ( 1 ) - C ( 2 ) N ( 2 ) - C ( 3 ) N ( 2 ) - C ( 3 ) C ( 2 ) - C ( 3 ) 1 .346(4) 1 .324(4) 1 . 372( 4) 1 . 375( 4) 1 .390(5) 1 .349 1 .326 1 . 375 1 .377 1 .395 C ( 5 ) - C ( 6 ) C ( 6 ) - C ( 7 ) C ( 7 H C ( 8 ) C ( 8 ) - C ( 8 a ) 1.368(4) 1.408(4) 1.364(4) 1.406(4) T a b l e 111 — 1 . Non-Hydrogen C o n t a i n i n g Bond L e n g t h s of AHQSA ( i n An g s t r o m s ) Bonds A n g l e ( d e g ) Bonds A n g l e ( d e g ) 0( 1 - S - 0 ( 2 ) 111. 84(14) C ( 4 ) - C ( 4 a ) - C ( 8 a ) 1 19. 7(3) 0 ( T - S -0(3) 112. 86(14) C ( 5 ) - C ( 4 a ) - C ( 8 a ) 118. 0(3) 0( 1 -S-C(7) 106. 24(14) 0 ( 4 ) - C ( 5 ) - C ( 4 a ) 115. 3(3) 0 ( 2 - S -0(3) 113. 49(15) 0 ( 4 ) - C ( 5 ) - C ( 6 ) 1 25. 2(3) 0 ( 2 -S-C(7) 105. 45(14) C ( 4 a ) - C ( 5 ) - C ( 6 ) 1 19. 5(3) 0 ( 3 -S-C(7) 1 06. 23(13) C ( 5 ) - C ( 6 ) - C ( 7 ) 1 20. 6(3) C(2 - N ( 1 ) - C ( 8 a ) 1 24. 4(3) S - C ( 7 ) - C ( 6 ) 117. 9(2) N( 1 i - C ( 2 ) - C ( 3 ) 120. 7(3) S - C ( 7 ) - C ( 8 ) 1 19. 9(2) N(2 - C ( 3 ) - C ( 2 ) 1 20. 1 (3) C ( 6 ) - C ( 7 ) - C ( 8 ) 122. 1(3) N(2 - C ( 3 ) - C ( 4 ) 1 22. 1 (3) C ( 7 ) - C ( 8 ) - C ( 8 a ) 117. 6(3) C(2' - C ( 3 ) - C ( 4 ) 1 17. 8 ( 3 ) N ( 1 ) - C ( 8 a ) - C ( 4 a ) 1 T6. 5(3) C(3 - C ( 4 ) - C ( 4 a ) 1 20. 9(3) N(1 ) - C ( 8 a ) - C ( 8 ) 121. 2(3) C(4 - C ( 4 a ) - C ( 5 ) 1 22. 3(3) C ( 4 a ) - C ( 8 a ) - C ( 8 ) 122. 2(3) T a b l e 111-2 . Non H y d r o g e n - C o n t a i n i n g Bond A n g l e s of AHQSA ( D e g r e e s ) A g a i n , f o u r i s o l a t e d n o n - l a b i l e s i g n a l s were o b s e r v e d w i t h s m a l l o r no s p l i t t i n g , and w i t h c h e m i c a l s h i f t s s i m i l a r t o AHQSA. The IR s p e c t r u m showed the c h a r a c t e r i s t i c s t r o n g a b s o r b a n c e s of a s u l p h o n i c a c i d group and a r a t h e r b r o a d d o u b l e t i n t h e 3300 t o 80 Bond L e n g t h Bond L e n g t h ( A ) 0 ( 4 ) - H ( 0 4 ) 0 ( 5 ) - H ( 0 5 a ) 0 ( 5 ) - H ( 0 5 b ) N(1)-H(N1) N(2)-H(N2a) 0.78(4) 1.00(5) 0.85(4) 0.84(4) 0.95(4) N(2)-H(N2b) C ( 2 ) - H ( 2 ) C ( 4 ) - H ( 4 ) C ( 6 ) - H ( 6 ) C ( 8 ) - H ( 8 ) 0.91(5) 0.99(3) 0.87(3) 0.89(3) 0.88(3) T a b l e 111-3 . AHQSA Bond L e n g t h s I n v o l v i n g Hydrogen Atoms ( i n Ang s t r o m s ) Bonds A n g l e ( d e g ) Bonds A n g l e ( d e g ) C ( 5 ) - 0 ( 4 ) - H ( 0 4 ) 111(3) C ( 3 ) - C ( 2 ) - H(2) 121(2') H ( 0 5 a ) - 0 ( 5 ) - H ( 0 5 b ) 105(4) C ( 3 ) - C ( 4 ) - H(4) 120(2) C ( 2 ) - N ( 1 ) - H ( N 1 ) 119(3) C ( 4 a ) -C(4) -H(4) 118(2) C ( 8 a ) - N ( 1')-H(n1 ) 117(3) C ( 5 ) - C ( 6 ) - H(6) 118(2) C ( 3 ) - N ( 2 ) - H ( N 2 a ) 118(2) C ( 7 ) - C ( 6 ) - H(6) 121(2) C ( 3 ) - N ( 2 ) - H ( N 2 b ) 113(3) C ( 7 ) - C ( 8 ) - H(8) 120(2) H(N2a)-N(2)-H(N2b) 127(4) C ( 8 a ) -C(8) -H(8) 122(2) N( 1 ) - C ( 2 ) - H ( 2 ) 118(2) T a b l e I I I - 4 . AHQSA Bond A n g l e s I n v o l v i n g Hydrogen Atoms ( D e g r e e s ) 3500 cm" 1 r e g i o n t h a t i s t y p i c a l of am i n e s . One o b v i o u s d i f f e r e n c e between t h e IR s p e c t r a of t h i s compound and AHQSA, was t h a t t h e s t r o n g C-0 a r o m a t i c p h e n o l a b s o r b a n c e a t 1400 cm"' p r e s e n t i n t h e l a t t e r was not o b s e r v e d i n t h e f o r m e r . On t h e b a s i s of t h e above i n f o r m a t i o n i t was c o n c l u d e d t h a t t h i s c o - p r o d u c t must e i t h e r have two s u l p h o n i c a c i d g r o u p s and one amino g r o u p , o r one s u l p h o n i c a c i d and two amines as s u b s t i t u e n t s on a q u i n o l i n e r i n g s y s t e m . The p a t t e r n of s u b s t i t u t i o n would have t o be 3, 5 and 7 a g a i n i n o r d e r t o g i v e 81 t h e o b s e r v e d NMR s p e c t r u m . Two s u l p h o n i c a c i d g r o u p s were u n l i k e l y , b e c a u s e t h e r e l a t i v e i n t e n s i t y of t h e s u l p h o n i c a c i d IR a b s o r b a n c e s t o t h e a r o m a t i c a b s o r b a n c e s were a b o u t t h e same a s t h e s e p a r a m e t e r s m e a s u r e d i n t h e AHQSA s p e c t r u m . The 3,5 d i a m i n o , 7 - s u l p h o n i c a c i d a r r a n g e m e n t was d e c i d e d on, b e c a u s e t h i s i s v e r y s i m i l a r i n s t r u c t u r e t o AHQSA. T h e , r e p l a c e m e n t o f t h e h y d r o x y l g r o u p by an amine i s v e r y r e a s o n a b l e a n d w o u l d e v e n be e x p e c t e d u n d e r t h e r e a c t i o n c o n d i t i o n s ( s e e s e c t i o n I I I -C ( 1 ) ) . The s t r u c t u r e o f 3,5 d i a m i n o , 7 - q u i n o l i n e s u l p h o n i c a c i d a s i s o l a t e d , a n d a f t e r a c i d i f i c a t i o n i s shown i n F i g u r e 111-8. F i g u r e I I I - 8 . Ammonium S a l t and A c i d Forms o f 3 , 5 - D i a m i n o - 7 -q u i n o l i n e s u l p h o n a t e I I I - B . The R e a c t i o n o f Some M o d e l Compounds w i t h ( N H a ) j , S 0 3 i n C o n c e n t r a t e d N H „ O H J u s t a s c a t e c h i n was u s e d a model o f c o n i f e r b a r k p o l y f l a v a n o i d s , i t was f o u n d n e c e s s a r y t o u s e -models and 82 a n a l o g u e s of c a t e c h i n , i n o r d e r t o f u r t h e r u n d e r s t a n d t h e n a t u r e of t h e r e a c t i o n w i t h ( N H 4 ) 2 S 0 3 . F o r example, t h e b e h a v i o u r of p h l o r o g l u c i n o l under the c l e a v a g e r e a c t i o n c o n d i t i o n s would g i v e i n f o r m a t i o n on how t h e c a t e c h i n A - r i n g i s m o d i f i e d . I t was f o u n d t h a t an u n d e r s t a n d i n g of a r e p l a c e m e n t r e a c t i o n named a f t e r B u c h e r e r was i n i t i a l l y n e c e s s a r y . A d i s c u s s i o n o f t h i s r e a c t i o n i s p r e s e n t e d f i r s t . (1) The B u c h e r e r R e a c t i o n on R e s o r c i n o l and P h l o r o g l u c i n o l In t h e p r e s e n c e o f s u l p h i t e or b i s u l p h i t e i o n s and h e a t i n ammonia s o l u t i o n , c e r t a i n h y d r o x y l a t e d a r o m a t i c compounds can be c o n v e r t e d t o a m i n e s . The r e v e r s e r e a c t i o n a l s o o c c u r s ; i . e . , a n i l i n e d e r i v a t i v e s can be c o n v e r t e d to p h e n o l s i n a l k a l i n e s u l p h i t e s o l u t i o n . T hese i n t e r c o n v e r s i o n s p r o c e e d by t h e B u c h e r e r r e a c t i o n . Compounds t h a t w i l l u ndergo t h i s p r o c e s s a r e l i m i t e d t o d e r i v a t i v e s o f n a p h t h a l e n e ( 1 1 0 ) , q u i n o l i n e ( 1 11,112), r e s o r c i n o l (113,114) and r e l a t e d compounds. Com m e r c i a l a p p l i c a t i o n s of t h e B u c h e r e r r e a c t i o n have been r e s t r i c t e d t o t h e s y n t h e s i s of n a p h t h a l e n e d e r i v a t i v e s used i n t h e m a n u f a c t u r e of d yes ( 1 1 0 ) . A c c o r d i n g l y , much of t h e more modern work on t h e mechanism of t h i s r e a c t i o n has been done u s i n g n a p h t h a l e n e and n a p h t h y l a m i n e s r a t h e r t h a n m o n o c y c l i c p h e n o l s . The c o n d i t i o n s r e q u i r e d f o r t h e c o n v e r s i o n of a s u i t a b l e 83 p h e n o l t o an a n i l i n e d e r i v a t i v e - a h o t ammonia s o l u t i o n c o n t a i n i n g s u l p h i t e i o n - a r e t h e same t h a t a r e needed f o r t h e c l e a v a g e of t a n n i n s o r c a t e c h i n i n t o c a t e c h o l and o t h e r p r o d u c t s . A s t u d y of t h e l a t t e r r e a c t i o n i s t h e main s u b j e c t of t h i s t h e s i s . In f a c t , t h e c l e a v a g e r e a c t i o n was f i r s t o b s e r v e d d u r i n g an e x p e r i m e n t t o d e t e r m i n e whether t h e p h l o r o g l u c i n o l i c A - r i n g of c a t e c h i n c o u l d be a m i n a t e d by t h i s r e a c t i o n . I t i s o b v i o u s t h a t an u n d e r s t a n d i n g of t h e B u c h e r e r r e a c t i o n c o u l d be h e l p f u l i n d e t e r m i n i n g t h e mechanism of t h e c l e a v a g e r e a c t i o n s t u d i e d h e r e . O r i g i n a l l y , i t was t h o u g h t t h a t t h e B u c h e r e r r e a c t i o n p r o c e e d e d by f o r m a t i o n of t h e b i s u l p h i t e a d d i t i o n p r o d u c t of t h e k e t o f o r m of a p h e n o l , w h i c h t h e n decomposed t o t h e amine ( F i g u r e I I I - 9 ) . T h i s mechanism was o r i g i n a l l y p r o p o s e d by F u c h s (115, 116). A l l t h e r e a c t i o n s t e p s a r e e q u i l i b r i a so t h e r e v e r s e t r a n s f o r m a t i o n , a n i l i n e t o p h e n o l d e r i v a t i v e , would go by t h e same mechanism, o n l y i n r e v e r s e . The most i m p o r t a n t e v i d e n c e t h a t s u p p o r t e d t h i s mechanism was t h e i s o l a t i o n of k e t o n e - d e r i v e d b i s u l p h i t e a d d i t i o n p r o d u c t s from p h l o r o g l u c i n o l ( 1 1 7 ) , r e s o r c i n o l (113) and o t h e r compounds. In t h e c a s e of r e s o r c i n o l , a c t i o n of t h e b i s u l p h i t e l e a d s t o t h e i n t r o d u c t i o n of a s u l p h o n a t e r e s i d u e i n a d d i t i o n t o t h e ones a t t h e c a r b o n y l c a r b o n s ( F i g u r e 111 — 10) . The ' mechanism d e s c r i b e d above was l a t e r q u e s t i o n e d by R i e c h e and S e e b o t h , a t l e a s t f o r t h e 2 - n a p h t h o l s ( 1 1 8 , 1 1 9 ) . They showed t h a t t h e b i s u l p h i t e a d d u c t t h a t can be i s o l a t e d from n a p h t h o l s a r e not 1,1-hydroxy s u l p h o n a t e s t r u c t u r e s , but a r e i n 84 F i g u r e 111-9. The Mechanism of t h e B u c h e r e r R e a c t i o n A c c o r d i n g t o F u c h s (116) F i g u r e 111 — 10. S t r u c t u r e of t h e B i s u l p h i t e A d d i t i o n P r o d u c t s of P h l o r o g l u c i n o l and R e s o r c i n o l f a c t /3-keto s u l p h o n a t e s . A summary of t h e mechanism a c c o r d i n g t o t h e s e w o r k e r s i s shown i n F i g u r e 111 — 11 . The e v i d e n c e used t o s u p p o r t t h i s mechanism does not e x c l u d e t h e p o s s i b i l i t y of an i n t e r m e d i a t e l i k e t h e s u l p h i t e 85 F i g u r e 111 — 11 . The Mechanism o f t h e B u c h e r e r R e a c t i o n on N a p h t h o l s A c c o r d i n g t o S e e b o t h (119) a d d i t i o n p r o d u c t shown i n F i g u r e 111-9. T h e r e has been no d i r e c t e v i d e n c e f o r t h e gem-amino, h y d r o x y i n t e r m e d i a t e ( S t r u c t u r e 3, F i g u r e 111 — 11) p o s t u l a t e d by S e e b o t h . The compound t h a t was i s o l a t e d i s a t e t r a l o n e -s u l p h o n i c a c i d ( s t r u c t u r e 2, F i g u r e 111 — 11). In t h e r e a c t i o n s o l u t i o n , t h i s t y p e of compound p r o b a b l y e x i s t s a s t h e b i -b i s u l p h i t e a d d u c t w h i c h decomposes t o t h e k e t o form d u r i n g t h e i s o l a t i o n p r o c e d u r e . One s t e p i n t h e workup of t h e s e compounds i s t r e a t i n g w i t h HC1 gas t o d r i v e o f f S 0 2 ( 1 1 9 ) . S i n c e b i s u l p h i t e a d d i t i o n p r o d u c t s of k e t o n e s decompose i n even m i l d a c i d ( 1 2 0 ) , t h i s i s p r o b a b l y t h e p o i n t a t w h i c h th e f o r m a t i o n of t h e f r e e t e t r a l o n e s u l p h o n i c a c i d s o c c u r s . The e x a c t n a t u r e of t h e i n t e r m e d i a t e i n which t h e oxygen g r o u p i s r e p l a c e d by a n i t r o g e n g r o u p , has not y e t been d e t e r m i n e d . 86 The r a t e a t w h i c h t h e B u c h e r e r r e a c t i o n p r o c e e d s , and i n f a c t whether i t p r o c e e d s a t a l l , w i l l depend' on t h e r a t e of t h e s t e p i n which t h e a r o m a t i c i t y of t h e s u b s t i t u t e d r i n g i s l o s t . T a b l e 111-5 shows t h e r e s o n a n c e e n e r g y ( r . e . ) o f some a r o m a t i c o r g a n i c compounds. T h i s number p r o v i d e s a measure o f t h e d e g r e e of a r o m a t i c s t a b i l i z a t i o n of a g i v e n compound. Th e s e v a l u e s a r e d e t e r m i n e d by t a k i n g t h e d i f f e r e n c e between th e c a l c u l a t e d and o b s e r v e d h e a t s of c o m b u s t i o n . A l t h o u g h t h e r e a r e p r o b l e m s w i t h t h e a s s u m p t i o n s r e q u i r e d i n c a l c u l a t i n g t h e t h e o r e t i c a l h e a t of c o m b u s t i o n f o r an a r o m a t i c compound, the s t a b i l i z a t i o n e n e r g y can be u s e d t o o b t a i n a good q u a l i t a t i v e i d e a of t h e d e g r e e of e l e c t r o n d e r e a l i z a t i o n ( 1 2 1 ) . S u b s t a n c e Resonance E n e r g y ( K c a l / m o l e ) Benzene 36.0 n - P r o p y l Benzene 35.4 S t y r e n e 38. 1 N a p h t h a l e n e 61 .0 Pyr i d i n e 23.0 Q u i n o l i n e 47.3 P h e n o l 36.0 A n i 1 i n e 38.0 2 - N a p h t h o l 61.0 R e s o r c i n o l 36.0 P h l o r o g l u c i n o l 36.0 T a b l e I I I - 5 . Resonance E n e r g i e s of Some A r o m a t i c Compounds (122) K i n e t i c s t u d i e s have shown t h a t t h e r a t e of t h e B u c h e r e r r e a c t i o n f o r n a p h t h o l s depends on t h e a d d i t i o n of b i s u l p h i t e t o a C=C and not a C-0 l i n k a g e ( 1 2 4 , 1 2 5 ) . T h i s e v i d e n c e s u p p o r t s 87 S e e b o t h ' s mechanism, where b i s u l p h i t e adds f i r s t t o t h e s u b s t i t u t e d r i n g and d e s t r o y s i t s a r o m a t i c i t y . The r e s u l t i n g e n o l t a u t o m e r i z e s t o a k e t o n e ( F i g u r e 111 — 12). The a d d i t i o n of th e s e c o n d b i s u l p h i t e t o t h e c a r b o n y l c a r b o n would h e l p s t a b i l i z e t h e compound and push t h e e q u i l i b r i a t o t h e non-a r o m a t i c s i d e . The change i n r e s o n a n c e e n e r g y i n t h i s r e a c t i o n s e r i e s would be about t h e same as t h e d i f f e r e n c e i n r . e . ' s f o r 2 - n a p h t h o l and n - p r o p y l b e n z e n e : 61-35.4 = 25.6 K c a l / m o l e . T h i s i s s t i l l a s u b s t a n t i a l e n e r g y b a r r i e r , but t h e r e i s a n o t h e r f a c t o r t h a t has t o be t a k e n i n t o a c c o u n t . Summation of bond e n e r g i e s shows t h a t t h e k e t o form of a ta u t o m e r p a i r , >CH-C=0, i s 10 t o 16 k c a l / m o l e more s t a b l e t h a n t h e e n o l , >C=C-OH, d e p e n d i n g on t h e method of c a l c u l a t i o n ( 1 2 3 , 1 2 6 ) . I f we assume an a v e r a g e e n e r g y d i f f e r e n c e between k e t o and e n o l forms of 13 K c a l / m o l e , t h e e n e r g y change between 2 - n a p h t h o l and t h e t e t r a l o n e s u l p h o n i c a c i d would be 61-35.4-13 = 12.6 K c a l / m o l e . Of c o u r s e , a l l t h e s e numbers a r e a p p r o x i m a t i o n s and can o n l y be us e d i n a s e m i q u a n t i t a t i v e manner. However t h i s does i n d i c a t e why a mononaphthol w i l l r e a c t but p h e n o l w i l l n o t . In t h e l a t t e r c a s e t h e d i f f e r e n c e i n e n e r g y between t h e a r o m a t i c e n o l and n o n - a r o m a t i c ketone forms would be 36-13 = 23 K c a l / m o l e , a v a l u e a l m o s t t w i c e as l a r g e as c a l c u l a t e d f o r 1 - n a p h t h o l . The g r e a t e r s t a b i l i t y of t h e k e t o form e x p l a i n s t h e r e l a t i v e r e a c t i v i t i e s of p h e n o l , r e s o r c i n o l and p h l o r o g l u c i n o l under B u c h e r e r r e a c t i o n c o n d i t i o n s . P h e n o l i s u n r e a c t i v e , r e s o r c i n o l i s r e l a t i v e l y r e a c t i v e and p h l o r o g l u c i n o l i s v e r y r e a c t i v e . F o r a r e a c t i o n t i m e of 2 h o u r s a t 175° C, about 50% 88 F i g u r e 111- 12. A d d i t i o n of B i s u l p h i t e t o 2 - N a p h t h o l o f t h e r e s o r c i n o l p r e s e n t i s c o n v e r t e d i n t o 3-amino p h e n o l and a b o u t 5% i n t o t h e d i a m i n o d e r i v a t i v e . Under th e same c o n d i t i o n s p h l o r o g l u c i n o l i s c o n v e r t e d t o 1 , 3 , 5 - t r i a m i n o b e n z e n e i n a b o u t 80% y i e l d . The e n e r g y d i f f e r e n c e between th e e n o l and k e t o forms of r e s o r c i n o l i s 36-13-13=10 K c a l / m o l e . T h i s v a l u e i s c o m p a r a b l e t o n a p h t h o l , and t h e r e a c t i v i t y o f t h e s e two compounds i s s i m i l a r . A 95% y i e l d o f 2 - n a p h t h y l a m i n e i s o b t a i n e d a f t e r r e a c t i o n a t 150° C f o r 8 h o u r s ( 1 1 0 ) . The b i s u l p h i t e a d d u c t of r e s o r c i n o l ( F i g u r e 111 — 10) a l s o had a d d i t i o n of b i s u l p h i t e t o t h e r i n g i n t h e 5 p o s i t i o n w h i c h i s s i m i l a r t o t h e i s o l a t e d a d d u c t of 1 - n a p h t h o l . Whether th e b i s u l p h i t e added f i r s t t o t h e r i n g o r t o a c a r b o n y l of t h e r e s o r c i n o l , i s not known. P h l o r o g l u c i n o l has t h r e e e n o l s so t h e e n e r g y d i f f e r e n c e i n t h i s c a s e w i l l be n e g a t i v e , 36—13—13—13=—3 K c a l / m o l e . The n e g a t i v e v a l u e i n d i c a t e s t h a t a t room t e m p e r a t u r e a l a r g e 89 p r o p o r t i o n o f t h e p h l o r o g l u c i n o l m o l e c u l e s s h o u l d be i n t h e k e t o f o r m . T h i s i s not o b s e r v e d i n t h e s o l i d or i n s o l u t i o n a l t h o u g h many r e a c t i o n s of p h l o r o g l u c i n o l r e q u i r e t h a t i t f i r s t t a u t o m e r i z e t o t h e k e t o form ( 1 2 6 ) . The s e m i q u a n t i t a t i v e n a t u r e o f t h i s t y p e of c a l c u l a t i o n i s shown h e r e . O t h e r f a c t o r s s u c h as t h e e x t e n t and s t r e n g t h of s o l v e n t - p h e n o l h y d r o g e n - b o n d i n g u n d o u b t e d l y have an e f f e c t b ut a r e not t a k e n i n t o a c c o u n t . From t h i s a n a l y s i s , t h e r e a p p e a r t o be two f a c t o r s t h a t can make an a r o m a t i c compound amenable t o a m i n a t i o n v i a t h e B u c h e r e r r e a c t i o n . F i r s t , i f t h e a r o m a t i c r i n g t o w h i c h t h e h y d r o x y l i s bonded has s u f f i c i e n t l y low a r o m a t i c c h a r a c t e r , b i s u l p h i t e can add t o t h e r i n g , d e s t r o y i n g i t s a r o m a t i c i t y and a l l o w i n g t h e e n o l t o t a u t o m e r i z e t o i t s k e t o form. The k e t o n e can t h e n r e a c t t o form t h e i m i n e , and, a f t e r l o s s of t h e b i s u l p h i t e , an a n i l i n e d e r i v a t i v e . T h i s s i t u a t i o n o c c u r s w i t h m o n o n a p h t h o l s . F o r p h l o r o g l u c i n o l and r e l a t e d compounds, t h e l o s s of a r o m a t i c i t y i s c a u s e d by t h e a d d i t i o n o f s u l p h i t e t o a c a r b o n y l c a r b o n of t h e k e t o form of t h e p h e n o l . T h i s i n t e r m e d i a t e goes on t o form t h e a m i n a t e d p r o d u c t . Whether or not a m i n a t i o n a t t h e c a r b o n y l s p r o c e e d s by an a m i n o - s u l p h o n i c a c i d i n t e r m e d i a t e i s not known. However, i t has been o b s e r v e d t h a t p h l o r o g l u c i n o l can be a m i n a t e d i n t h e a b s e n c e of s u l p h i t e when kept a t room t e m p e r a t u r e i n ammonia s o l u t i o n f o r s e v e r a l d a y s ( 1 2 3 ) . The p r e s e n c e of s u l p h i t e does s p e e d t h e r e a c t i o n up. However, i t may do t h i s s i m p l y by d e s t r o y i n g t h e a r o m a t i c i t y of t h e r i n g and not f o r m i n g t h e a c t u a l r e a c t i v e i n t e r m e d i a t e . F o r t h i s t y p e o f p h e n o l a m i n a t i o n t o o c c u r , t h e k e t o form of t h e p h e n o l must be 90 r e l a t i v e l y s t a b l e . I f n e i t h e r of t h e s e c o n d i t i o n s a r e met -t h a t i s , t h e h y d r o x y l i s a s u b s t i t u e n t on a r i n g w i t h a h i g h r e s o n a n c e e n e r g y and i t has a weak ke t o n e c h a r a c t e r - t h e n a m i n a t i o r i d o e s n ' t o c c u r . P h e n o l i t s e l f i s an example of t h i s t y p e of compound. Of c o u r s e t h e s e same arguments would be t r u e f o r c o n v e r s i o n o f a r o m a t i c amines t o p h e n o l s . The q u e s t i o n of what i s t h e a c t u a l mechanism f o r t h e s u b s t i t u t i o n of a h y d r o x y l by an amino f u n c t i o n i s s t i l l l e f t u n r e s o l v e d . T h e r e i s no f i r m e v i d e n c e f o r e i t h e r r o u t e (summarized i n F i g u r e I I I — 1 3 ) . However, mechanism A seems t o O H ^ C ^ E M H N H 2 A. = X = 5<OH=s5<N^ X = A Mechan i sm A ? H M W N H 2 Mechan ism B F i g u r e 111 — 13. Two P o s s i b l e S u b s t i t u t i o n Mechanisms have been b a s e d s o l e l y on t h e f a c t t h a t gem-hydroxy, s u l p h i t e a d d i t i o n p r o d u c t s of p h l o r o g l u c i n o l and r e s o r c i n o l can be i s o l a t e d . The o b s e r v a t i o n t h a t a p h e n o l w i t h s t r o n g k e t o n e 91 c h a r a c t e r l i k e p h l o r o g l u c i n o l c a n be a m i n a t e d i n t h e a b s e n c e o f s u l p h i t e s u g g e s t s t h a t t h e s u l p h i t e may a c t as a c a t a l y s t by d e s t r o y i n g t h e r i n g a r o m a t i c i t y b u t not p a r t i c i p a t e i n t h e a c t u a l a m i n a t i o n . The a d d i t i o n o f ammonia t o a l d e h y d e s t o f o r m a d d u c t s and t h e r e a c t i o n o f a m i n e s w i t h k e t o n e s t o f o r m i m i n e s a r e w e l l known t r a n s f o r m a t i o n s ( F i g u r e 1 1 1 - 1 4 ) . T h i s e v i d e n c e s u p p o r t s mechanism B as t h e method by w h i c h a r o m a t i c h y d r o x y l s a r e r e p l a c e d by an amino f u n c t i o n . O H e o o I // I ^ I R C + N H 3 ' R C — N H 3 ' » R C N H , \ H H H R ' R ' O H R ' H R ' \ : = 0 + N H 2 — R " = • « N C = N ^ © ^ V = N R X R y N H R " R ' R " R X N R " F i g u r e 111-14. The R e a c t i o n o f Ammonia and Amines w i t h C a r b o n y l Compounds (120) (2) C a t e c h o l B a s e d on t h e s t r u c t u r a l s i m i l a r i t i e s between c a t e c h o l and r e s o r c i n o l , i t w o u l d be r e a s o n a b l e t o assume t h a t t h e s e two 92 compounds w i l l behave i n a s i m i l a r manner u n d e r B u c h e r e r r e a c t i o n c o n d i t i o n s . I n f a c t , t h e e x t e n t o f a m i n a t i o n was f o u n d t o be q u i t e d i f f e r e n t . W h i l e r e s o r c i n o l i s a p p r o x i m a t e l y 50% a m i n a t e d when r e a c t e d f o r 0.5 h o u r s a t 175° C, c a t e c h o l d o e s n o t r e a c t a t a l l . T h i s d i f f e r e n c e c a n n o t be e x p l a i n e d i n t e r m s o f r e s o n a n c e v e r s u s k e t o n e s t a b i l i z a t i o n e n e r g y , a s b o t h compounds have t h e same r e s o n a n c e s t a b i l i z a t i o n and two h y d r o x y l s c a p a b l e o f e n o l i z i n g t o k e t o n e s . The d i f f e r e n c e a p p e a r s t o l i e i n t h e i n h e r e n t s t a b i l i t i e s o f t h e k e t o f o r m s o f t h e two p h e n o l s ( F i g u r e 1 1 1 - 1 5 ) . F i g u r e 111-15. K e t o - e n o l E q u i l i b r i a o f C a t e c h o l a n d R e s o r c i n o l T h i s d i f f e r e n c e c a n be s e e n i n a c o m p a r i s o n o f 1,3 and 1,2 c y c l o h e x a d i o n e s ( T a b l e I I I - 6 ) . I n a q u e o u s s o l u t i o n , t h e f o r m e r i s a l m o s t e n t i r e l y e n o l i c w h i l e t h e l a t t e r i s m a i n l y i n t h e k e t o f o r m . The same t r e n d c a n be s e e n i n t h e a l i c y c l i c compounds 93 Compound Percent Enol Ketone Enol in Dilute Water Solution Ref. o OH ^ JL -0 127 0 o A A O PH XX 20 128 40 129 o o & -100 130 ^ ^ O H O u Cr or -100 129 T a b l e 111 — 6. C o n c e n t r a t i o n of t h e E n o l T a u t o m e r s of Some D i k e t o n e s i n Aqueous S o l u t i o n 94 a c e t y l a c e t o n e and b i a c e t y l . I t seems p r o b a b l e t h a t t h e same s i t u a t i o n o c c u r s i n t h e monoketo t a u t o m e r of c a t e c h o l and r e s o r c i n o l . S t r u c t u r e V would be more s t a b l e t h a n I I . In t h e a n a l y s i s done i n t h e p r e v i o u s s e c t i o n f o r r e s o r c i n o l , i t was assumed t h a t t h e most s t a b l e n o n - a r o m a t i c form would be t h e d i k e t o n e . S i n c e i t seems t h a t t h e monoketo form of 1,3 d i k e t o n e s i s more s t a b l e , t h e e n e r g y d i f f e r e n c e between th e a r o m a t i c and n o n - a r o m a t i c t a u t o m e r s must be even l e s s t h a n t h e 10 K c a l / m o l e c a l c u l a t e d above f o r r e s o r c i n o l . T h i s shows t h e r e l a t i v e c r u d e n e s s of t h e s e c a l c u l a t i o n s . The f a c t o r t h a t has been i g n o r e d i s t h e r e s o n a n c e s t a b i l i z a t i o n i n th e n o n - a r o m a t i c monoketo i s o m e r . F o r r e s o r c i n o l , t h e r e s o n a n c e s t a b i l i z a t i o n e n e r g y o f t h e mono-enol must be g r e a t e r t h a n t h e a p p r o x i m a t e l y ' 13 K c a l / m o l e t h a t would be g a i n e d by t a u t o m e r i z i n g t o t h e d i k e t o i s o m e r . In c o m p a r i n g r e s o r c i n o l and c a t e c h o l f o r th e s a t u r a t e d d i k e t o n e s , t h e r e s o n a n c e s t a b i l i z a t i o n e n e r g y of th e mono-enol forms s h o u l d be a b o u t the same. S i n c e i t i s o b s e r v e d t h a t t h i s i s not t r u e , t h e r e must be a n o t h e r f a c t o r i n v o l v e d h e r e . One p o s s i b l e e x p l a n a t i o n f o r t h e d i f f e r e n t s t a b i l i t i e s of t h e monoketo forms of t h e two d i h y d r o x y p h e n o l s i n v o l v e s t h e e l e c t r o s t a t i c r e p u l s i o n of the d i p o l e moments of t h e 1,2 c a r b o n y l o r a l c o h o l g r o u p s when t h e y a r e c o p l a n a r . F o r b i a c e t y l , t h i s r e p u l s i o n seems t o be g r e a t e r t han t h e s t a b i l i z a t i o n o f t h e mono-enol form w i t h h y d r o g e n b o n d i n g between t h e oxygen g r o u p s ( F i g u r e I I I — 1 6 ) , and e x p l a i n s why t h i s compound has no e n o l i c c h a r a c t e r a t a l l . 95 O p V / C — C H / \ C H 3 C H 3 F i g u r e 111 — 1 6. H y d r o g e n - B o n d i n g i n t h e Mono-Enol T a u t o m e r s of A c y c l i c D i k e t o n e s In 1 , 2 - c y c l o h e x a n e d i o n e t h e c a r b o n y l s a r e f o r c e d t o be a p p r o x i m a t e l y c o p l a n a r . To r e d u c e t h e e l e c t r o s t a t i c r e p u l s i o n , one of t h e c a r b o n y l s c an t a u t o m e r i z e t o t h e e n o l form, i n w h i c h th e a l c h o h o l g r o u p would have a s m a l l e r d i p o l e moment t h a n >C=0. ' The h y d r o g e n - b o n d i n g p o s s i b l e i n t h i s t a u t o m e r w i l l a l s o h e l p s t a b i l i z e i t . The r e s u l t i s t h a t , i n s o l u t i o n , a bout 40% of t h i s compound i s i n t h e mono-enol form. F o r 1,2-c y c l o p e n t a d i o n e , where t h e r i n g i s v e r y c l o s e t o b e i n g p l a n a r , t h e r e p u l s i o n between t h e c a r b o n y l s w i l l be even g r e a t e r and a l a r g e r p r o p o r t i o n of t h e compound w i l l be f o r c e d i n t o t h e e n o l f o r m . As n o t e d b e f o r e ( T a b l e I I I - 6 ) , 1 , 2 - c y c l o p e n t a d i o n e i s e n t i r e l y i n t h e mono-enol form i n s o l u t i o n . From t h i s r e a s o n i n g , i t f o l l o w s t h a t c a t e c h o l i s l e s s r e a c t i v e t h a n r e s o r c i n o l t o a m i n a t i o n v i a t h e B u c h e r e r r e a c t i o n b e c a u s e t h e most s t a b l e n o n - a r o m a t i c c a t e c h o l t a u t o m e r i s not as II I C H 3 C C H 3 1 F o r example, t h e d i p o l e moments of f o r m a l d e h y d e and m e t h a n o l i n th e gas phase a r e 2.33 and 1.70 d e b y e s , r e s p e c t i v e l y ( 1 31 ) . 96 s t a b l e as t h e c o r r e s p o n d i n g r e s o r c i n o l i s o m e r . The g r e a t e r s t a b i l i t y o f t h e l a t t e r means t h a t t h e e n e r g y b a r r i e r t o t h e n o n - a r o m a t i c s u l p h o n a t e d i n t e r m e d i a t e i s s m a l l . Thus, r e s o r c i n o l i s more r e a c t i v e under t h e s e c o n d i t i o n . (3) W a t t l e Bark E x t r a c t As shown i n F i g u r e 1-18, w a t t l e bark p o l y f l a v a n o i d s have a d i f f e r e n t h y d r o x y l s u b s t i t u t i o n p a t t e r n from c a t e c h i n o r w e s t e r n hemlock b a r k f l a v a n o i d s . I n s t e a d of t h e p h l o r o g l u c i n o l i c A-r i n g , t h i s p a r t of t h e monomeric u n i t of t h e w a t t l e t a n n i n i s d e r i v e d from r e s o r c i n o l . R e a c t i o n of w a t t l e b a r k e x t r a c t w i t h ( N H „ ) 2 S 0 3 / N H 3 a t 175° C f o r two h o u r s not o n l y p r o d u c e d c a t e c h o l as e x p e c t e d , b u t a l s o r e s o r c i n o l and some h y d r o x y a n i l i n e d e r i v a t i v e s . A n a l y s i s of t h e v o l a t i l e a r o m a t i c s p r o d u c e d i n t h i s r e a c t i o n was done by GC-MS. The c o m p u t e r i z e d s p e c t r a s e a r c h r o u t i n e used t o i d e n t i f y t h e p r o d u c t s c o u l d not d i s t i n g u i s h between 3-aminophenol and 2 - a m inophenol o r t h e c o r r e s p o n d i n g d i a m i n a t e d p r o d u c t s . In o r d e r t o d e t e r m i n e whether t h e s e a n i l i n e d e r i v a t i v e s were o r t h o or meta s u b s t i t u t e d , t h e GC r e t e n t i o n t i m e s were compared t o the p r o d u c t s o b t a i n e d from t h e a m i n a t i o n of r e s o r c i n o l . The r e t e n t i o n t i m e s were a p p r o x i m a t e l y t h e same, i n d i c a t i n g t h a t t h e h y d r o x y - a n i 1 i n e and d i a m i n o b e n z e n e i s o l a t e d from t h e w a t t l e e x t r a c t r e a c t i o n were meta s u b s t i t u t e d and so d e r i v e d from r e s o r c i n o l . T h i s c o n c l u s i o n was v e r i f i e d by c o - i n j e c t i o n of t h e 97 a c e t y l a t e d p r o d u c t s from b o t h r e a c t i o n s . At t h e a p p r o p r i a t e r e t e n t i o n t i m e s o n l y one peak was o b s e r v e d . The r a t i o of t h e peak a r e a s due t o r e s o r c i n o l , 3 -amino-phenol and 1,3-d i a m i n o p h e n o l were a p p r o x i m a t e l y t h e same i n b o t h r e a c t i o n s . The c o n c l u s i o n t h a t can be drawn from t h e s e d a t a i s t h a t , i n w a t t l e t a n n i n p o l y f l a v a n o i d s , b o t h th e A- and B - r i n g s can be c l e a v e d o f f . T h i s o b s e r v a t i o n p r o v i d e d v a l u a b l e c l u e s i n t h e d e t e r m i n a t i o n of t h e mechanism of t h e c l e a v a g e r e a c t i o n . I I I - C . A Mechanism f o r t h e C l e a v a g e of C a t e c h i n i n t o C a t e c h o l and Q u i n o l i n e D e r i v a t i v e s The p r o d u c t s t h a t have been i s o l a t e d from t h e c l e a v a g e of c a t e c h i n a r e shown i n F i g u r e 111-1 7. Compound I can be i s o l a t e d i n l a r g e r q u a n t i t i e s t h an II and i s assumed t o be t h e major c o -p r o d u c t of c a t e c h o l . I t i s o b v i o u s t h a t t h e c a t e c h o l must be d e r i v e d from t h e B - r i n g and t h e two q u i n o l i n e p r o d u c t s from the A- and C - r i n g s of c a t e c h i n . In l i g h t o f t h e d i s c u s s i o n on t h e B u c h e r e r r e a c t i o n , t h e r e l a t i o n s h i p between I and ,11 i s q u i t e c l e a r . A m i n a t i o n of t h e p h l o r o g l u c i n o l i c A - r i n g has s i m p l y p r o c e e d e d t o a g r e a t e r e x t e n t i n I I . The l a t t e r compound c a n n o t be d i r e c t l y p r o d u c e d from the 5-hydroxy d e r i v a t i v e ( s e e F i g u r e 111 — 18 f o r numbering s y s t e m ) , as i t was o b s e r v e d t h a t h e a t i n g p u r e I w i t h s u l p h i t e i n ammonia does not p r o d u c e I I . In r e t r o s p e c t , t h i s r e s u l t s h o u l d have been e x p e c t e d , s i n c e t h e benzene r i n g of t h e q u i n o l i n e c o u l d e n o l i z e o n l y a t t h e 5-98 O H HO-O H O H HOjS-+ O H N H 2 O H I N H 2 n F i g u r e 111 — 17 . Major P r o d u c t s from t h e C l e a v a g e of C a t e c h i n p o s i t i o n so i t s k e t o t a u t o m e r would be r e l a t i v e l y u n s t a b l e . The p o s i t i o n meta t o t h e h y d r o x y l ( C - 7 ) , where t h e s u l p h i t e would add i n a n a p h t h a l e n e - t y p e mechanism, i s a l r e a d y o c c u p i e d by a s u l p h o n i c a c i d g r o u p . A s e c o n d s u l p h u r g r o u p a d d i n g t o t h i s p o s i t i o n would be v e r y u n l i k e l y due t o s t e r i c h i n d r a n c e . I t i s e v i d e n t t h a t t h e 7 - a m i n a t i o n must o c c u r a t some i n t e r m e d i a t e s t a g e i n t h e c l e a v a g e r e a c t i o n . The p r o b a b l e p o i n t i n the r e a c t i o n s e quence where t h i s a m i n a t i o n would o c c u r i s m e n t i o n e d below. In t h e c o n v e r s i o n of c a t e c h i n t o I and c a t e c h o l , t h e r e a r e some s u b s t i t u t i o n s and o t h e r r e a c t i o n s t h a t must o c c u r : (1) B r e a k i n g of the C2-C9 e t h e r bond. (2) S u b s t i t u t i o n of t h e C9 h y d r o x y l by an amino g r o u p . (3) F o r m a t i o n of a s e c o n d a r y amine between C2 and C9. (4) B r e a k i n g of t h e C2-C1' bond. 99 e 1 4 F i g u r e 111 — 18. S t a n d a r d N u m b e r i n g S y s t e m F o r Q u i n o l i n e D e r i v a t i v e s (5) S u b s t i t u t i o n o f t h e C7 h y d r o x y l by a s u l p h o n i c a c i d g r o u p . (6) D e h y d r o g e n a t i o n t o f o r m a d o u b l e bond between C3 and C4. (7) S u b s t i t u t i o n o f t h e C3 h y d r o x y l by an amino g r o u p . T h e s e s t e p s a r e n o t n e c e s s a r i l y p r e s e n t e d i n t h e o r d e r i n w h i c h t h e y w o u l d o c c u r i n t h e c o m p l e t e r e a c t i o n . The b r e a k i n g o f t h e c a t e c h i n e t h e r l i n k a g e p r o b a b l y o c c u r s f i r s t . T h i s r e a c t i o n h a s been i n v e s t i g a t e d by o t h e r w o r k e r s and p r o b a b l y p r o c e e d s by t h e m echanism shown i n F i g u r e 111 — 1 t o f o r m a C2 s u l p h o n a t e d d e r i v a t i v e . As m e n t i o n e d e a r l i e r , i t was d e m o n s t r a t e d t h a t t h i s compound i s an i n t e r m e d i a t e i n t h e c l e a v a g e r e a c t i o n t o c a t e c h o l . I t c o u l d be i s o l a t e d when c a t e c h i n was r e a c t e d w i t h s u l p h i t e i n ammonia s o l u t i o n a t low t e m p e r a t u r e . I f a p o r t i o n o f t h e s o l u t i o n c o n t a i n i n g t h e r i n g -o p e n e d compound was t h e n r e h e a t e d a t 175° C, c a t e c h o l and t h e q u i n o l i n e compounds a r e o b t a i n e d i n y i e l d s c o m p a r a b l e t o t h e d i r e c t r e a c t i o n o f c a t e c h i n w i t h ( N H „ ) 2 S 0 3 / N H 3 . 1 00 (1) A m i n a t i o n on t h e P h l o r o g l u c i n o l i c A - R i n g The a m i n a t i o n a t C9 c o u l d o n l y o c c u r a f t e r t h e p y r a n B - r i n g had been opened. At t h i s p o i n t t h e A - r i n g would t a k e on many of t h e c h a r a c t e r i s t i c s of p h l o r o g l u c i n o l i n c l u d i n g i t s s t r o n g k e t o n e c h a r a c t e r . The i n i t i a l a d d i t i o n o f s u l p h i t e would p r o b a b l y o c c u r a t t h e l e a s t s t e r i c a l l y h i n d e r e d p o s i t i o n - p a r a t o t h e a l k y l g r o u p . A m i n a t i o n c o u l d t h e n p r o c e e d a t t h e o t h e r two s i t e s ( s e e F i g u r e I I I — 1 9 ) . T h i s i s t h e p o i n t a t w h i c h t h e C5 a m i n a t i o n may o c c u r and d e t e r m i n e s whether t h e f i n a l q u i n o l i n e p r o d u c t i s 3 - a m i n o - 5 - h y d r o x y - 7 - q u i n o l i n e s u l p h o n i c a c i d ( I ) o r 3,5 d i a m i n o , 7 - q u i n o l i n e s u l p h o n i c a c i d ( I I ) . (2) A m i n a t i o n a t C3 L o o k i n g backwards from t h e f i n a l p r o d u c t s , t h e most l i k e l y p o i n t f o r t h e a m i n a t i o n a t C3 t o o c c u r would be a t t h e end of t h e s equence a f t e r t h e a r o m a t i c q u i n o l i n e s t r u c t u r e has been formed. The B u c h e r e r r e a c t i o n has been r e p o r t e d t o o c c u r w i t h q u i n o l i n e d e r i v a t i v e s , a l t h o u g h o n l y compounds w i t h t h e h y d r o x y l on t h e benzene r i n g have been i n v e s t i g a t e d (111, 112). In t h i s c a s e , t h e h y d r o x y l i s on t h e p y r i d i n e r i n g . C a l c u l a t i o n of t h e e n e r g y d i f f e r e n c e between the a r o m a t i c and k e t o forms of a j3-h y d r o x y q u i n o l i n e u s i n g v a l u e s from T a b l e 111-5 g i v e s a v a l u e of -1.1 K c a l / m o l e : 101 NH 2 F i g u r e 111- 19. I n t r o d u c t i o n of t h e C5 and C9 Amino Groups 102 4 7 . 3 ( r . e . of q u i n o l i n e ) - 3 5 . 4 ( r . e . of B e n z e n e ) - 1 3 ( K e t o n e s t a b i l i z a t i o n e n e r g y ) = -1.1 K c a l / m o l e The s m a l l n e g a t i v e number i n d i c a t e s t h a t t h e k e t o form would be r e l a t i v e l y s t a b l e . In f a c t , i t has been r e p o r t e d t h a t b i s u l p h i t e e a s i l y adds t o p y r i d i n e i t s e l f a t t h e 4 p o s i t i o n ( 1 3 2 ) . W i t h t h i s i n f o r m a t i o n , t h e a m i n a t i o n can be e n v i s a g e d t o o c c u r as shown i n F i g u r e 111-20. F i g u r e 111-20. A Mechanism F o r t h e A m i n a t i o n a t C3 1 03 (3) D e h y d r o g e n a t i o n a t C3-C4 When t h e s t r u c t u r e o f t h e q u i n o l i n e p r o d u c t i s compared t o th e c a t e c h i n s t a r t i n g m a t e r i a l , i t i s e v i d e n t t h a t a d e h y d r o g e n a t i o n must o c c u r a t some p o i n t i n i t s f o r m a t i o n . One of t h e d o u b l e bonds i n t h e h e t e r o c y c l i c r i n g c o u l d r e s u l t from t h e e l i m i n a t i o n of t h e B - r i n g , b u t t h e o t h e r c o u l d o n l y be formed i n some o x i d a t i o n s t e p , s i n c e t h e r e i s no o t h e r change i n th e s u b s t i t u t i o n p a t t e r n i n t h e A- and C- r i n g r e s i d u e s . T h e r e a r e a t l e a s t t h r e e ways i n w h i c h - t h i s d e h y d r o g e n a t i o n c o u l d o c c u r : (a) O x i d a t i o n by an i n o r g a n i c c o n s t i t u e n t o f t h e r e a c t i o n s o l u t i o n . (b) O x i d a t i o n by m o l e c u l a r o x ygen. (c) D i s p r o p o r t i o n a t i o n . In s t r o n g l y b a s i c s o l u t i o n , t h e s u l p h i t e i o n has a s t r o n g r e d u c i n g a c t i o n ( 1 3 3 ) . Of c o u r s e , s u l p h a t e c an a c t as an S O „ - 2 + H 20 + 2e" - S 0 3 - 2 + 20H~ E = -0.92 o x i d i z i n g a g e n t by t h e r e v e r s e o f t h i s h a l f - r e a c t i o n . However, s u l p h a t e i s p r e s e n t o n l y as a v e r y minor i m p u r i t y i n t h e ( N H „ ) 2 S 0 3 u s e d as t h e r e a g e n t and c o u l d o n l y a c t w i t h a r e l a t i v e l y s t r o n g r e d u c i n g a g e n t . The p o s s i b i l i t y of an i n o r g a n i c o x i d a t i o n c an be r u l e d o u t . A t m o s p h e r i c oxygen has been known t o a c t as an o x i d i z i n g a g ent of a l k e n e s ( 1 3 4 ) . T h i s p o s s i b i l i t y was t e s t e d u s i n g d i f f e r e n t r e a c t i o n c o n d i t i o n s . In one c a s e , t h e s o l u t i o n 1 04 c o n t a i n i n g c a t e c h i n , s u l p h i t e and ammonia was s a t u r a t e d w i t h n i t r o g e n by s l o w l y b u b b l i n g t h e gas t h r o u g h t h e r e a c t i o n s o l u t i o n . An N 2 atmosphere was k ept i n t h e t u b e w h i l e i t was f l a m e - s e a l e d . In t h i s way t h e e x t e n t of t h e r e a c t i o n i n t h e a b s e n c e o f oxygen c o u l d be t e s t e d . A n o t h e r t u b e was p r e p a r e d i n t h e same way but u s i n g oxygen g a s . In t h i s c a s e t h e r e a c t i o n would p r o c e e d i n t h e p r e s e n c e of a l a r g e q u a n t i t y o f o x y g e n . A t h i r d c o n t r o l tube was a l s o p r e p a r e d i n t h e u s u a l manner w i t h no gas b u b b l i n g done a t a l l . T h e r e was no s i g n i f i c a n t d i f f e r e n c e i n t h e amount of c a t e c h o l p r o d u c e d from t h e t h r e e e x p e r i m e n t a l s o l u t i o n s a f t e r r e a c t i o n a t 175° C. The o b v i o u s c o n c l u s i o n i s t h a t oxygen does not p a r t i c i p a t e i n t h e c l e a v a g e of c a t e c h i n t o c a t e c h o l and q u i n o l i n e d e r i v a t i v e s . D i s p r o p o r t i o n a t i o n . i s an a u t o - o x i d a t i o n r e a c t i o n whereby one m o l e c u l e of a compound o x i d i z e s a n o t h e r i d e n t i c a l o r c l o s e l y r e l a t e d m o l e c u l e . The r e s u l t i s two p r o d u c t s , one w i t h a h i g h e r and t h e o t h e r w i t h a l o w e r o x i d a t i o n s t a t e t h a n t h e s t a r t i n g m a t e r i a l . Some examples of d i s p r o p o r t i o n a t i o n a r e g i v e n i n F i g u r e 111 — 21 . In t h e t h i r d example the q u i n o n e s t a r t i n g m a t e r i a l o x i d i z e s i t s a d d i t i o n p r o d u c t t o form t h e s u b s t i t u t e d n a p h t h o q u i n o n e . The p o t e n t i a l of t h e s u b s t i t u t e d q u i n o n e p r o d u c t i s much l e s s t h a n t h a t o f t h e s t a r t i n g m a t e r i a l , so t h e r e a c t i o n i s e s s e n t i a l l y q u a n t i t a t i v e ; two moles of n a p h t h o q u i n o n e a r e r e q u i r e d t o p r o d u c e one mole of t h e s u b s t i t u t e d p r o d u c t . Q u i n o n e s can a c t as v e r y e f f i c i e n t d e h y d r o g e n a t i n g a g e n t s . The i n t e r m e d i a t e formed i n t h e s u l p h o n a t i o n of c a t e c h i n 1 05 g u r e 111-21. Examples of D i s p r o p o r t i o n a t i o n 1 06 ( s e e F i g u r e 111 — 1) i s c a l l e d a q u i n o n e m e t h i d e . T h i s t y p e of •compound u n d e r g o e s many of t h e r e a c t i o n s of q u i n o n e s and c o u l d a l s o be. e x p e c t e d t o a c t i n a s i m i l a r manner i n s e l f - o x i d a t i o n r e a c t i o n s . D i s p r o p o r t i o n a t i o n seems t o be t h e most l i k e l y mechanism f o r t h e o x i d a t i o n s t e p i n t h e c l e a v a g e p r o c e s s . L i k e l y p o i n t s a t w hich t h i s s t e p c o u l d o c c u r a r e p r e s e n t e d l a t e r . (4) C l e a v a g e o f t h e C2-C1' Bond T h i s i s t h e most i m p o r t a n t s t e p i n t h e c l e a v a g e mechanism, s i n c e i t i s t h e p o i n t a t w h i c h t h e c a t e c h o l m o l e c u l e i s formed. Methods f o r t h e b r e a k i n g of c a r b o n - c a r b o n bonds a r e r e l a t i v e l y few i n number and u s u a l l y o c c u r o n l y w i t h a good l e a v i n g g r o u p . At f i r s t g l a n c e , t h e c a t e c h o l B - r i n g of c a t e c h i n a p p e a r s t o be a p o or c a n d i d a t e f o r t h i s f u n c t i o n . However, a t t h e h i g h t e m p e r a t u r e and b a s i c c o n d i t i o n s r e q u i r e d f o r t h i s c l e a v a g e r e a c t i o n , t h e c a t e c h o l r i n g w i l l t a u t o m e r i z e r a p i d l y . One of t h e t a u t o m e r i c forms ( I I I , F i g u r e 111-2 2) would be a r e l a t i v e l y good e l e c t r o n - a c c e p t o r and l e a v i n g - g r o u p . One p o s s i b l e mechanism f o r b r e a k i n g t h e C2-C1' bond i s a s i m p l e / 3 - e l i m i n a t i o n as shown i n F i g u r e 111-23. The d e h y d r o g e n a t i o n a t C3-C4 would have t o o c c u r f i r s t , so t h e d r i v i n g f o r c e f o r the e l i m i n a t i o n would be t h e f o r m a t i o n of t h e s t a b l e q u i n o l i n e a r o m a t i c s t r u c t u r e . However, t h i s mechanism i s u n l i k e l y b e c a u s e i t w i l l not work f o r e l i m i n a t i o n o f t h e A - r i n g F i g u r e 111 — 23 . F o r m a t i o n of C a t e c h o l by 0 - E l i m i n a t i o n as was o b s e r v e d i n the w a t t l e b a r k t a n n i n . I t i s n o t p o s s i b l e <> 108 t o end up w i t h an a r o m a t i c p r o d u c t from A - r i n g e l i m i n a t i o n s i n c e t h e c a t e c h o l B - r i n g does not have a h y d r o x y l g r o u p o r t h o t o t h e C2-C1' bond t h a t can be a m i n a t e d t o e v e n t u a l l y f o r m t h e n i t r o g e n i n t h e q u i n o l i n e h e t e r o c y c l i c r i n g . A n o t h e r mechanism would have t o be p r o p o s e d f o r A - r i n g c l e a v a g e t h a t would a l s o e x p l a i n why p h l o r o g l u c i n o l ( o r 1 , 3 , 5 - t r i a m i n o b e n z e n e ) i s n o t formed from c a t e c h i n . A l s o , / 3 - e l i m i n a t i o n does n o t s u g g e s t how t h e r a t h e r anomolous s u b s t i t u t i o n s of t h e h y d r o x y l a t C7 w i t h s u l p h i t e o c c u r s . The b r e a k i n g of t h e C2-C1' bond and t h e s u b s t i t u t i o n r e a c t i o n a r e b o t h u n e x p e c t e d and l i k e l y t o be l i n k e d i n some way. T h i s makes an e l i m i n a t i o n mechanism l i k e t h i s u n l i k e l y . The o b s e r v a t i o n t h a t t h e c l e a v a g e can go e i t h e r way i n w a t t l e t a n n i n t o form r e s o r c i n o l and c a t e c h o l i s a v e r y i m p o r t a n t one. i f t h e c o m p l i c a t i o n o f two d i f f e r e n t mechanisms f o r A- and B - r i n g c l e a v a g e s i s t o be a v o i d e d , t h e n t h e c l e a v a g e w i l l have t o o c c u r a t a r a t h e r s y m m e t r i c a l i n t e r m e d i a t e . The 1, 3 - d i a r e n e - p r o p a n e s t r u c t u r e of s u l p h o n a t e d c a t e c h i n f u l f i l l s t h i s r e q u i r e m e n t . The e q u i v a l e n t s u l p h o n a t e d w a t t l e monomer (f i s e t i n i d o l ) . i s even more s y m m e t r i c a l s i n c e t h e two a r o m a t i c r i n g s a r e more s i m i l a r i n r e a c t i v i t y and s t r u c t u r e ( F i g u r e I I I -2 4 ) . As was m e n t i o n e d i n t h e p r e v i o u s s e c t i o n , t h e q u i n o n e -m e t h i d e i n t e r m e d i a t e i n t h e s u l p h o n a t i o n of c a t e c h i n c o u l d a c t as t h e o x i d i z i n g a g ent i n a d i s p r o p o r t i o n a t i o n r e a c t i o n . I f t h e s e l f - o x i d a t i o n was t o happen a t t h i s p o i n t , two p r o d u c t s would be formed, one of w h i c h would have an e x t e n d e d c o n j u g a t e d s t r u c t u r e ( F i g u r e I I I — 2 5 ) . S u l p h o n a t i o n of t h i s compound i s 1 09 SObH F i g u r e 111-24. S u l p h o n a t e d F i s e t i n i d o l most l i k e l y t o o c c u r a t t h e c a r b o n a l p h a t o t h e c a t e c h o l r i n g , b e c a u s e of t h e s t e r i c h i n d r a n c e of t h e h y d r o x y l g r o u p s o r t h o t o t h e c a r b o n c h a i n on t h e p h l o r o g l u c i n o l r i n g . W i t h a r e s o r c i n o l i c A - r i n g , t h e r e i s o n l y one o r t h o h y d r o x y l , so s u l p h o n a t i o n a t t h e A - r i n g a l p h a c a r b o n would p r o c e e d more r e a d i l y i n w a t t l e t a n n i n s . An e x t e n d e d t y p e of e l i m i n a t i o n can be e n v i s a g e d t o o c c u r i n t h e d e h y d r o g e n a t e d , C 2 - s u l p h o n a t e d c a t e c h i n (Route A, F i g u r e 1 1 1 - 2 6 ) . T h i s c l e a v a g e mechanism i s c l o s e l y r e l a t e d t o h e t e r o l y t i c f r a g m e n t a t i o n as d e s c r i b e d by G rob (138,139,140). In t h i s c l a s s of r e a c t i o n s , a m o l e c u l e s y m b o l i z e d by a-b-c-d-x c l e a v e s i n t o t h r e e f r a g m e n t s : a-b, c=d and x. The l e t t e r s a, b, c and d r e p r e s e n t a s equence of atoms s u c h as C, 0, N, S, P or B. B a s i c a l l y , t h e mechanism i n v o l v e s e l e c t r o n - d o n a t i o n from one end of t h e m o l e c u l e (a-b) t o a l e a v i n g g r o u p (x) w i t h t h e f o r m a t i o n of an u n s a t u r a t e d i n t e r m e d i a t e f r agment ( c = d ) . a-b-c-d-x *• a-b + c=d + x Some examples o f t h e t y p e s of compounds and t h e f r a g m e n t s 1 10 F i g u r e 111-25. D i s p r o p o r t i o n a t i o n o f t h e C a t e c h i n S u l p h o n a t i o n I n t e r m e d i a t e t h e y form d u r i n g h e t e r o l y t i c f r a g m e n t a t i o n a r e shown i n T a b l e 111 — 7. In t h e c a s e of t h e m o d i f i e d c a t e c h i n r e a c t i o n , t h e p h l o r o g l u c i n o l r i n g a c t s as t h e e l e c t r o n - d o n a t i n g g r o u p and t h e c a t e c h o l r i n g as t h e l e a v i n g g r o u p . The m i d d l e g r o u p does n o t p h y s i c a l l y s e p a r a t e from th e A - r i n g ; t h e r e i s j u s t a s h i f t i n t h e d o u b l e bonds. F o r c a t e c h i n , t h e c l e a v a g e a t t h e A - r i n g (Route B, F i g u r e 111-26) i s l e s s l i k e l y b e c a u s e o f : (1) S t e r i c h i n d r a n c e t o s u l p h o n a t i o n a t C4. (2) A h i g h e r e n e r g y b a r r i e r i n Route B. The a r o m a t i c i t y of t h e c a t e c h o l r i n g i s l o s t w hich r e q u i r e s a l a r g e r ' i n p u t of 111 . O H C o o, O H r < = 0 ^ O H F i g u r e 111-26. F o r m a t i o n of C a t e c h o l and P h l o r o g l u c i n o l by an E x t e n d e d E l i m i n a t i o n from S u l p h i t e d , D e h y d r o g e n a t e d C a t e c h i n e n e r g y as compared t o r o u t e A where t h e a r o m a t i c i t y o f t h e p h l o r o g l u c i n o l r i n g i s l o s t ( s e e s e c t i o n s 111-B.(1) and ( 2 ) ) . (3) The i n a b i l i t y of t h e n o n - a r o m a t i c p r o d u c t o f Route B t o s t a b i l i z e by r e a r r a n g e m e n t t o an a r o m a t i c p r o d u c t ( s e e b e l o w ) . The f i r s t two r e a s o n s l i s t e d do not a p p l y w i t h a r e s o r c i n o l i c A - r i n g , and so e x p l a i n why more of t h e Route B t y p e Electron-Donating Groups Middle Groups Leaving Groups a — b — a — b — c — d — c=-d — X X 1 H O — C -1 o = c ' \ 1 1 — C — C — 1 1 — C l C l 1 RjN — C — 1 © / R „ N = C \ 1 — o— c— 1 o=cy — O H 2 H 2 0 1 H O — C II O o=c=o 1 -c—o— 1 — OS0 2Ar i e S 0 3 A r 1 Ar — C — 1 / Ar — C © \ \ 1 N — C — / | — O C O R e O C O R e 1 —c—c— 1 /c \ Vc' — C s C — © — N R 3 N R 3 a — b — c — d — x — a — b + c =d + x T a b l e I I I - 7 . E x a m p l e s o f Some Common E l e c t r o n - D o n a t i n g , M i d d l e a n d L e a v i n g G r o u p s F o u n d i n Compounds U n d e r g o i n g H e t e r o l y t i c F r a g m e n t a t i o n ( 1 3 8 , 1 3 9 ) 113 r e a c t i o n t o c l e a v e o f f t h e A - r i n g o c c u r s i n t h e c l e a v a g e of w a t t l e t a n n i n . (5) Rearrangement of t h e N o n - A r o m a t i c C a t e c h i n C l e a v a g e P r o d u c t As m e n t i o n e d p r e v i o u s l y , k e t o n e s form an a d d i t i o n p r o d u c t v e r y r e a d i l y i n c o n c e n t r a t e d s u l p h i t e s o l u t i o n . T h i s i s a l s o l i k e l y t o happen w i t h t h e q u i n o n e m e t h i d e c l e a v a g e p r o d u c t . A mechanism f o r t h e a d d i t i o n and s u b s e q u e n t r e a r r a n g e m e n t of t h e a m i n a t e d n o n - a r o m a t i c c l e a v a g e p r o d u c t t o a s u l p h o n a t e d q u i n o l i n e i s p r e s e n t e d i n F i g u r e 111-27. At C7, t h e h y d r o x y l i s l o s t , r a t h e r t h a n t h e s u l p h i t e , b e c a u s e t h e l a t t e r i s a l r e a d y n e g a t i v e l y c h a r g e d . T h e r e would be a s t r o n g e l e c t r o s t a t i c r e p u l s i o n t o t h e a d d i t i o n of a n o t h e r e l e c t r o n p a i r t o t h e s u l p h i t e g r o u p . The d r i v i n g f o r c e f o r t h e f i n a l e l i m i n a t i o n of b i s u l p h i t e ( s t e p 3) i s t h e s u b s e q u e n t f o r m a t i o n of t h e a r o m a t i c q u i n o l i n e s y s t e m . A r e l a t e d r e a c t i o n has been d e s c r i b e d by L a u e r and Langkammerer ( 1 4 1 ) . T h e s e a u t h o r s d e m o n s t r a t e d t h e f o r m a t i o n o f 3 - p h e n o l s u l p h o n i c a c i d from t h e a c t i o n o f sodium b i s u l p h i t e on r e s o r c i n o l ( s e e F i g u r e 111-28). A summary showing th e key i n t e r m e d i a t e s i n t h e p r o p o s e d mechanism f o r t h e c l e a v a g e of c a t e c h i n t o c a t e c h o l and 3-amino-5 - h y d r o x y - 7 - q u i n o l i n e s u l p h o n i c a c i d i s p r e s e n t e d i n F i g u r e I I I -29. 1 1 4 F i g u r e 111-27. Rearrangement of t h e N o n - A r o m a t i c C l e a v a g e P r o d u c t t o a S u b s t i t u t e d Q u i n o l i n e (6) C l e a v a g e of D i h y d r o q u e r c e t i n In an a t t e m p t t o t e s t t h e c l e a v a g e mechanism d e s c r i b e d above f o r c a t e c h i n , a r e l a t e d compound, d i h y d r o q u e r c e t i n (DHQ), was s u b j e c t e d t o t h e same r e a c t i o n c o n d i t i o n s , and t h e n a t u r e and y i e l d o f t h e p r o d u c t s examined. The C - r i n g o f DHQ i s i n a h i g h e r o x i d a t i o n s t a t e t h a n t h e c o m p a r a b l e p a r t of t h e c a t e c h i n m o l e c u l e s i n c e t h e r e i s a k e t o n e a t C4. I t was t h o u g h t t h a t i n t h i s c a s e t h e C4 k e t o n e would t a u t o m e r i z e t o an e n o l , making d i s p r o p o r t i o n a t i o n u n n e c e s s a r y t o g e t t o a c l e a v a b l e i n t e r m e d i a t e . I f t h i s d i d o c c u r , th e y i e l d o f c a t e c h o l s h o u l d d o u b l e , s i n c e i t would not be n e c e s s a r y f o r h a l f of t h e s t a r t i n g m a t e r i a l t o a c t as an o x i d i z i n g a g e n t . The r e d u c e d p r o d u c t o f t h e d i s p r o p o r t i o n a t i o n shown i n F i g u r e 111-29 c a n n o t p r o c e e d by t h e p r o p o s e d mechanism t o form c a t e c h o l . I t was e x p e c t e d t h a t 1 1 5 F i g u r e 111-28. The F o r m a t i o n o f 3 - P h e n o l s u l p h o n i c A c i d From R e s o r c i n o l (141) DHQ would r e a c t as shown i n F i g u r e 111-30. In f a c t , no c a t e c h o l a t a l l was o b s e r v e d i n t h e p r o d u c t m i x t u r e . The o n l y s o l v e n t - e x t r a c t a b l e p r o d u c t o b s e r v e d was 1 , 3 , 5 ~ t r i a m i n o b e n z e n e , t h e B u c h e r e r r e a c t i o n p r o d u c t of p h l o r o g l u c i n o l . What a p p e a r s t o have happened i s t h a t t h e k e t o n e formed a s u l p h i t e a d d i t i o n p r o d u c t f i r s t t h a t p r e v e n t e d any p o s s i b l e e n o l i z a t i o n . Even i n i t s u n d e r i v a t i z e d form, the k e t o n e p r o b a b l y has v e r y l i t t l e e n o l i c c h a r a c t e r due t o t h e h y d r o g e n b o n d i n g p o s s i b i l i t i e s w i t h a h y d r o x y l on t h e A - r i n g . In t h e a d d u c t form, a d o u b l e bond c a n n o t form between C3 and C4, so t h e mechanism f o r c a t e c h o l f o r m a t i o n d e s c r i b e d above i s not p o s s i b l e . However A - r i n g c l e a v a g e i s p o s s i b l e and does appear t o o c c u r . A mechanism f o r p h l o r o g l u c i n o l f o r m a t i o n from DHQ i s 1 1 6 F i g u r e 111-29. Key I n t e r m e d i a t e s i n t h e P r o p o s e d Mechanism f o r the C l e a v a g e of C a t e c h i n t o C a t e c h o l and 3-Amino-5-hydroxy-7-q u i n o l i n e s u l p h o n i c A c i d 1 1 7 F i g u r e 111-30. The E x p e c t e d R e a c t i o n Sequence of D i h y d r o q u e r c e t i n w i t h ( N H a ) 2 S 0 3 / N H 3 1 18 F i g u r e 111-31. A Mechanism f o r t h e P r o d u c t i o n of P h l o r o g l u c i n o l from D i h y d r o q u e r c e t i n 1 19 o u t l i n e d i n F i g u r e 1 1 1 — 31 . (7) C l e a v a g e of W e s t e r n Hemlock Bark T a n n i n The r e a c t i o n mechanism d e s c r i b e d above f o r t h e c l e a v a g e of c a t e c h i n s h o u l d a l s o a p p l y t o t h e c l e a v a g e of c a t e c h i n - b a s e d t a n n i n s due t o t h e i r s t r u c t u r a l s i m i l a r i t i e s . However, the p o l y m e r i c n a t u r e of t h e l a t t e r , m a t e r i a l w i t h t h e i r g l o b u l a r , t i g h t l y p a c k e d c o n f o r m a t i o n c o u l d c a u s e a c c e s s i b i l i t y p r o b l e m s . S u l p h i t e has t o be a b l e t o r e a c h C2 and C7 and t h e d i s p r o p o r t i o n a t i o n s t e p would have s t e r i c r e q u i r e m e n t s as w e l l . T h ese f a c t o r s would c o n t r i b u t e t o t h e o b s e r v e d l o w e r y i e l d of c a t e c h o l from w e s t e r n hemlock t a n n i n s . I t i s w e l l known t h a t c o n i f e r t a n n i n s r a p i d l y d e g r a d e a f t e r t r e e h a r v e s t i n g and d r y i n g of t h e b a r k o r a f t e r e x t r a c t i o n by o r g a n i c s o l v e n t s . The d e g r a d a t i o n a p p e a r s t o be due t o p o l y m e r i z a t i o n r e a c t i o n s t h a t r a i s e t h e a v e r a g e t a n n i n m o l e c u l a r w e i g h t . T h i s was t h e c a u s e of t h e r e d u c e d c a t e c h o l y i e l d s .from aged b a r k . The b e s t r e s u l t s were o b t a i n e d w i t h f r e s h m a t e r i a l . I s o l a t i o n by s o l v e n t e x t r a c t i o n a l s o seems t o a f f e c t t h e p o l y m e r s t r u c t u r e as t h e h i g h e s t c a t e c h o l y i e l d (see C h a p t e r I I ) was o b t a i n e d u s i n g f r e s h whole bark r a t h e r t h a n an e t h a n o l e x t r a c t . GC-MS a n a l y s i s of t h e s o l v e n t - e x t r a c t a b l e p h e n o l i c s formed from t h e c l e a v a g e of w e s t e r n hemlock b a r k t a n n i n s , showed the major p r o d u c t s t o be c a t e c h o l and p h e n o l . M i n o r p r o d u c t s o b s e r v e d were m e t h y l p h e n o l , m e t h o x y p h e n o l and d i m e t h o x y p h e n o l . 1 20 P a r a - h y d r o x y b e n z o i c a c i d has been r e p o r t e d t o be an a l k a l i f u s i o n p r o d u c t of w e s t e r n hemlock b a r k t a n n i n (17) wh i c h i m p l i e s t h a t a c e r t a i n p r o p o r t i o n of t h e B - r i n g s i n t h e t a n n i n polymer a r e m o n o - h y d r o x y l a t e d . P h e n o l would be p r o d u c e d from t h e s e g r o u p s d u r i n g t h e c l e a v a g e r e a c t i o n r a t h e r t h a n c a t e c h o l . T h i s e x p l a i n s t h e p h e n o l o b s e r v e d i n t h e r e a c t i o n p r o d u c t m i x t u r e . The o t h e r p h e n o l i c s , a s w e l l as a c e r t a i n p r o p o r t i o n of t h e c a t e c h o l and p h e n o l , a r e p r o b a b l y p r o d u c e d from t h e d e c a r b o x y l a t i o n of t h e c o r r e s p o n d i n g p a r a - h y d r o x y c a r b o x y l i c a c i d s , most of wh i c h have been r e p o r t e d t o be a component of w e s t e r n hemlock bark ( s e e F i g u r e 1-3). Under t h e c l e a v a g e r e a c t i o n c o n d i t i o n s , p r o t o c a t e c h u i c a c i d d e c a r b o x y l a t e s t o form c a t e c h o l i n h i g h y i e l d . I I I - D . Summary A mechanism f o r t h e c l e a v a g e r e a c t i o n o f c a t e c h i n was p r o p o s e d p a r t i a l l y b a s e d on t h e s t r u c t u r e s of an i n t e r m e d i a t e and two c a t e c h o l c o - p r o d u c t s . A low t e m p e r a t u r e r e a c t i o n of c a t e c h i n w i t h ammonium s u l p h i t e formed 1 - ( 3 , 4 - d i h y d r o x y p h e n y l ) -2 - h y d r o x y - 3 - ( 1 , 3 , 5 - t r i h y d r o x y p h e n y l ) p r o p a n e s u l p h o n i c a c i d . I f h e a t e d t o 175° C w i t h t h e ammonium s u l p h i t e r e a g e n t , t h i s compound r e a c t s f u r t h e r t o g i v e c a t e c h o l , showing t h a t i t i s an i n t e r m e d i a t e i n t h e c l e a v a g e of c a t e c h i n . The two c o - p r o d u c t s i s o l a t e d a l o n g w i t h c a t e c h o l were 3-amino-5-hydroxy-7-q u i n o l i n e s u l p h o n i c a c i d and 3 , 5 - d i a m i n o - 7 - q u i n o l i n e s u l p h o n i c 121 a c i d . O t h e r i n f o r m a t i o n on t h e r e a c t i o n mechanism o f c a t e c h i n came from t h e i d e n t i f i c a t i o n o f r e a c t i o n p r o d u c t s o b t a i n e d undpr t h e same c o n d i t i o n s from r e l a t e d compounds s u c h as p h l o r o g l u c i n o l , d i h y d r o q u e r c e t i n and w a t t l e t a n n i n . The r e a c t i o n r e q u i r e m e n t s o f h i g h t e m p e r a t u r e , h i g h c o n c e n t r a t i o n of ammonia and t h e p r e s e n c e of s u l p h i t e i o n a r e t h e same as t h o s e needed f o r t h e B u c h e r e r r e a c t i o n , a c l a s s i c s u b s t i t u t i o n r e a c t i o n by w h i c h c e r t a i n h y d r o x y l a t e d a r o m a t i c compounds can be c o n v e r t e d t o a n i l i n e d e r i v a t i v e s and v i c e  v e r s a . An u n d e r s t a n d i n g of t h i s r e a c t i o n p r o v e d t o be c r i t i c a l i n u n d e r s t a n d i n g th e c l e a v a g e of c a t e c h i n . The r e a c t i o n mechanism e n v i s a g e d f o r t h e c l e a v a g e of c a t e c h i n i n t o c a t e c h o l i s summarized below (See F i g u r e 111-29). (1) O p e n i n g of t h e c a t e c h i n C - r i n g t o g i v e t h e i s o l a t e d 2-s u l p h o n i c a c i d i n t e r m e d i a t e . (2) D i s p r o p o r t i o n a t i o n of t h e q u i n o n e - m e t h i d e i n e q u i l i b r i u m w i t h t h e s u l p h o n i c a c i d t o g i v e two p r o d u c t s w i t h t h e same c a r b o n backbone but i n d i f f e r e n t o x i d a t i o n s t a t e s . (3) A m i n a t i o n of t h e p h l o r o g l u c i n o l i c A - r i n g of t h e h i g h e r o x i d a t i o n s t a t e p r o d u c t v i a t h e B u c h e r e r r e a c t i o n . (4) C l e a v a g e t o form c a t e c h o l and a 9-carbon q u i n o n e m e t h i d e by a mechanism r e l a t e d t o h e t e r o l y t i c f r a g m e n t a t i o n . (5) C y c l i z a t i o n t o form a p a r t i a l l y a r o m a t i c b i c y c l i c compound. (6) L o s s of b i s u l p h i t e t o g i v e t h e f u l l y a r o m a t i c q u i n o l i n e s t r u c t u r e . 1 22 CHAPTER IV. FORMULATION OF ADHESIVES AND BOND EVALUATION The u n d e r l y i n g p u r p o s e of t h e r e s e a r c h p r e s e n t e d i n t h i s t h e s i s was t o d e v e l o p a c o m m e r c i a l l y f e a s i b l e a d h e s i v e from w e s t e r n hemlock b a r k . T h i s aim was a c c o m p l i s h e d i n t h a t c a t e c h o l , p r o d u c e d h e r e from t h e c l e a v a g e o f w e s t e r n hemlock t a n n i n , has been used s u c c e s s f u l l y i n a d h e s i v e a p p l i c a t i o n s by o t h e r w o r k e r s (101, 142). S i m p l y i s o l a t i n g c a t e c h o l from t h e r e a c t i o n m i x t u r e and t e s t i n g i t as an a d h e s i v e base would not have been u s e f u l as t h i s k i n d of work has a l r e a d y been done. I n s t e a d , t h e a d h e s i v e p r o p e r t i e s of t h e e n t i r e complex p r o d u c t m i x t u r e was e v a l u a t e d . I t was hoped t h a t t h e c a t e c h o l and o t h e r s i m p l e p h e n o l s p r o d u c e d would a c t as c r o s s l i n k i n g a g e n t s . The most s u c c e s s f u l t a n n i n - b a s e d a d h e s i v e s use a l o w - m o l e c u l a r w e i g h t PF r e s i n as a f o r t i f i e r ; m e t h y l o l a t e d - c a t e c h o l c o u l d f u l f i l l a s i m i l a r f u n c t i o n . The a p p r o a c h t o a d h e s i v e d e v e l o p m e n t u s e d i n t h i s work was t o f i r s t d e v e l o p t h e p r e p a r a t i o n c o n d i t i o n s and f o r m u l a t i o n components u s i n g a f a s t q u a l i t a t i v e method of bond e v a l u a t i o n . When good r e s u l t s were o b t a i n e d on a c o n s i s t e n t b a s i s , t h e n " f i n e - t u n i n g " was done u s i n g q u a n t i t a t i v e b o n d - t e s t i n g . In o r d e r t o m i n i m i z e t h e number of v a r i a b l e s , t h e same b a t c h of bark was u s e d i n a l l t h e b o n d i n g work. A f t e r c o l l e c t i o n , t h e bark was g r o u n d as q u i c k l y as p o s s i b l e and s t o r e d a t 0° C t o m a i n t a i n t h e q u a l i t y of t h e b a r k . 1 23 (1) Q u a l i t a t i v e A d h e s i v e Development The b a s i c t e c h n i q u e u s e d h e r e was t o bond two 10cm X 30cm s t r i p s of v e n e e r t o g e t h e r a t r i g h t a n g l e s so t h a t t h e r e was 100 cm 2 of g l u e l i n e . A f t e r c o o l i n g , t h e a s s e m b l y was m a n u a l l y t w i s t e d a p a r t and t h e q u a l i t y o f t h e bond e v a l u a t e d b a s e d on t h e e x t e n t of wood f a i l u r e . A 175° C p r e s s t e m p e r a t u r e and 2 m i n u t e p r e s s - t i m e were c h o s e n . T h e s e r a t h e r e x t r e m e p r e s s c o n d i t i o n s s h o u l d a l l o w f o r m a t i o n o f a good bond i f i t i s a t a l l p o s s i b l e , t h u s r e d u c i n g t h e number o f v a r i a b l e s i n v o l v e d . I f t h e r e s u l t s were e n c o u r a g i n g , t h e n m i l d e r c o n d i t i o n s c o u l d be i n v e s t i g a t e d . The c r u d e , a l k a l i - s o l u b l e r e a c t i o n m i x t u r e o b t a i n e d from t h e f i l t r a t i o n of t h e r e a c t e d b a r k s l u r r y was not u s e d 'as i s ' b e c a u s e of t h e low s o l i d s c o n t e n t and h i g h c o n c e n t r a t i o n of i n o r g a n i c i o n s ( ( N H , ) 2 S 0 3 ) . As w e l l as r e m o v i n g w a t e r , e v a p o r a t i o n o f t h e s o l u t i o n a l s o r e s u l t e d i n t h e l o s s of NH 3 and n e u t r a l i z a t i o n t o a b o u t pH 7.5. An a l k a l i - s o l u b l e p r e c i p i t a t e formed a t t h i s pH was f i l t e r e d o u t . T h i s m a t e r i a l was d e s i g n a t e d as t h e h i g h m o l e c u l a r w e i g h t f r a c t i o n (HMWF). To remove t h e e x c e s s ( N H „ ) 2 S 0 3 from t h e f i l t r a t e , e i t h e r e t h a n o l or a h o t aqueous s o l u t i o n of B a ( O H ) 2 was added and t h e p r e c i p i t a t e f i l t e r e d o u t . The a l c o h o l r e d u c e d t h e s o l u b i l i t y of t h e ( N H « ) 2 S 0 3 i n s o l u t i o n w h i l e t h e B a ( O H ) 2 formed B a S 0 3 w h i c h i s o n l y s l i g h t l y s o l u b l e i n c o l d w ater ( 0 . 0 2 g / l 0 0 m l a t 20° C, 143). The f i l t r a t e was e v a p o r a t e d t o g i v e t h e c a t e c h o l - c o n t a i n i n g o r g a n i c f r a c t i o n c a l l e d t h e low m o l e c u l a r w e i g h t f r a c t i o n (LMWF). In a d h e s i v e f o r m u l a t i o n , t h e two f r a c t i o n s were used i n t h e same r a t i o i n w h i c h t h e y were p r o d u c e d . 1 24 The g l u e f o r m u l a t i o n d e s c r i b e d by S t e i n e r and Chow (48) was u s e d as a s t a r t i n g p o i n t f o r t h e a d h e s i v e d e v e l o p m e n t : Bark E x t r a c t i v e s 70g (35% S o l i d s ) Modal 8g Wheat F l o u r 6g Water 1Og P a r a f o r m a l d e h y d e 6g pH - 6.5-7.0 Modal was not a v a i l a b l e , so CoCob was us e d as a f i l l e r i n s t e a d . U s i n g a f o r m u l a t i o n s i m i l a r t o t h e one above, t h e e f f e c t of pH on bond q u a l i t y was i n v e s t i g a t e d . I t was fo u n d t h a t t h e b e s t bond was o b t a i n e d w i t h a pH between 10 and 11. However, under t h e s e b a s i c c o n d i t i o n s i t was fo u n d t h a t p a r a -f o r m a l d e h y d e c o u l d not be us e d a s t h e f o r m a l d e h y d e s o u r c e , b e c a u s e i t c a u s e d r a p i d g e l l a t i o n of t h e a d h e s i v e . The l e s s r e a c t i v e f o r m a l d e h y d e s o u r c e , hexamine, had t o be used i n s t e a d . V a r y i n g t h e a s s e m b l y time showed t h a t t h e b e s t r e s u l t s were o b t a i n e d w i t h an open a s s e m b l y t i m e o f 20 t o 25 m i n u t e s . C l o s e d a s s e m b l y t i m e s were not i n v e s t i g a t e d . The l a s t i m p o r t a n t f o r m u l a t i o n p a r a m e t e r i n v e s t i g a t e d i n t h i s phase was t h e e f f e c t of a p r e - r e a c t i o n w i t h f o r m a l d e h y d e b e f o r e b o n d i n g . I t was hoped t h a t a p r e - r e a c t i o n of t h e low m o l e c u l a r w e i g h t f r a c t i o n would p r o d u c e m e t h y l o l a t e d c a t e c h o l and low m o l e c u l a r w e i g h t c a t e c h o l p o l y m e r s t h a t would a c t as c r o s s l i n k i n g a g e n t s between t h e l a r g e t a n n i n and t a n n i n r e s i d u e m o l e c u l e s . The LMWF was h e a t e d a t 100° C f o r v a r i o u s t i m e s up t o one hour w i t h about 20% 1 25 of t h e t o t a l f o r m a l d e h y d e t o be added (as p a r a f o r m a l d e h y d e ) a t pH 10.5. The r e s u l t i n g m e t h y l o l a t e d p h e n o l i c s o l u t i o n was th e n combined w i t h t h e HMWF, f i l l e r and hexamine, and t h e n t e s t e d . A p r e - r e a c t i o n t i m e of 1 hour gave t h e h i g h e s t bond s t r e n g t h . The b e s t a d h e s i v e , p r e p a r a t i o n p r o c e d u r e and f o r m u l a t i o n d e t e r m i n e d q u a l i t a t i v e l y was as f o l l o w s : 2 ml LMWF + 0.1 g NaOH + 0.14 g P a r a f o r m a l d e h y d e ( h e a t e d t o 100° C f o r 1 hour) 10 g HMWF 1 g H 20 1.2 g Hexamine 2 g Cocob 0.4 g Wheat F l o u r pH = 10.5, s o l i d s c o n t e n t - 4 5 % , A ssembly Time - 25 min Two-ply samples g l u e d w i t h t h i s a d h e s i v e gave v e r y good d r y s t r e n g t h ( a b o u t 95% wood f a i l u r e ) and wet s t r e n g t h w i t h some wood f a i l u r e . (2) Q u a n t i t a t i v e A d h e s i v e Development W i t h t h e q u a l i t a t i - v e d e v e l o p m e n t of t h e a d h e s i v e t o a r e a s o n a b l e l e v e l , t h e next s t e p was t o e v a l u a t e i t s s t r e n g t h and d e v e l o p i t f u r t h e r q u a n t i t a t i v e l y . Work on t h i s phase began a b o u t one month a f t e r t h e end of t h e de v e l o p m e n t d e s c r i b e d i n th e p r e v i o u s s e c t i o n ( a p p r o x i m a t e l y two months a f t e r c o l l e c t i o n 1 26 of t h e b a r k ) . A 1 2 X 1 8 i n c h t h r e e p l y p a n e l was p r e p a r e d u s i n g a l a r g e r s c a l e p r e p a r a t i o n of t h e a d h e s i v e f o r m u l a t i o n above, and t e s t e d f o r d r y and wet s h e a r s t r e n g t h . The r e s u l t s a r e summarized i n T a b l e I V - I . T h e s e were not t h e f i n d i n g s e x p e c t e d . The d r y s t r e n g t h was v e r y low and t h e s h e a r samples f e l l a p a r t w h i l e s o a k i n g i n w a t e r . Q u a l i t a t i v e t e s t i n g of t h i s f o r m u l a t i o n a l s o gave p o o r r e s u l t s . Dry S t r e n g t h Wet S t r e n g t h S h e a r Wood Shear Wood S t r e n g t h ( p s i ) F a i l u r e ( % ) S t r e n g t h ( p s i ) F a i l u r e ( % ) 1 25 1 0 0 0 1 05 1 0 0 0 80 0 0 0 85 0 0 0 90 0 0 0 1 70 20 0 0 90 5 0 0 95 5 0 0 1 45 20 0 0 90 0 0 0 80 0 0 0 T a b l e I V - 1 . R e s u l t s of Shear T e s t s On a T h r e e - P l y P a n e l A t f i r s t i t was t h o u g h t t h a t an e r r o r had been made e i t h e r i n t h e r e a c t i o n and p r e p a r a t i o n c o n d i t i o n s or i n t h e f o r m u l a t i o n . A n o t h e r b a t c h of a d h e s i v e was p r e p a r e d but a g a i n gave t h e same poor r e s u l t s . The b e s t e x p l a n a t i o n was t h a t t h e bark had d e g r a d e d i n s t o r a g e even though i t was k e p t i n a s e a l e d 1 2 7 . bag a t 0°' C. T h i s c o n c l u s i o n was c o n f i r m e d by t e s t i n g a s m a l l sample f o r c a t e c h o l y i e l d . O n l y about one q u a r t e r of t h e y i e l d from f r e s h bark was o b s e r v e d . I t was a l s o f o u n d t h a t p a r a f o r m a l d e h y d e c o u l d be u s e d i n s t e a d of hexamine i n t h e a d h e s i v e f o r m u l a t i o n . T h i s was a n o t h e r i n d i c a t i o n of t h e l o w e r r e a c t i v i t y o f t h e p r o d u c t s o b t a i n e d from t h e d e g r a d e d , o l d e r b a r k . More q u a n t i t a t i v e bond e v a l u a t i o n was done u s i n g t h e d e g r a d e d b a r k i n o r d e r t o g a i n more i n f o r m a t i o n a b o u t th e s y s t e m . In a l l c a s e s no wet s t r e n g t h was o b s e r v e d . The f i g u r e s r e p o r t e d a r e f o r d r y s t r e n g t h s o n l y . The r e s u l t s , w i t h a s t a t i s t i c a l a n a l y s i s a r e g i v e n i n t h e A p p e n d i x . F i r s t , r e a c t i o n p r o d u c t i s o l a t i o n s were done u s i n g d i f f e r e n t amounts o f B a ( O H ) 2 (30, 40 and 50 grams) t o p r e c i p i t a t e out t h e s u l p h i t e . U n i f o r m l y p o o r r e s u l t s were o b t a i n e d w i t h v e r y l i t t l e wood f a i l u r e . Next, the q u a l i t y of bonds p r o d u c e d u s i n g t h e e n t i r e r e a c t i o n p r o d u c t m i x t u r e , i n c l u d i n g u n r e a c t e d ammonium s u l p h i t e , were t e s t e d . A g a i n , poor r e s u l t s were o b t a i n e d , but i t was i n t e r e s t i n g t h a t t h e l a r g e s t amount of ammonium s u l p h i t e i n t h e r e a c t i o n m i x t u r e a l s o gave the b e s t bond s t r e n g t h . I t seems t h a t t h e a d d i t i o n a l s t r e n g t h r e s u l t i n g from t h e h i g h e r c o n c e n t r a t i o n of low m o l e c u l a r w e i g h t p r o d u c t s o b t a i n e d from t h e c l e a v a g e r e a c t i o n w i t h t h e h i g h e r ( N H „ ) 2 S 0 3 c o n c e n t r a t i o n overcame t h e d i s a d v a n t a g e of t h e h i g h e r i n o r g a n i c s a l t c o n c e n t r a t i o n . F i n a l l y , g l u e l i n e l o a d i n g s and p a r a f o r m a l d e h y d e • c o n t e n t s were e v a l u a t e d u s i n g a s m a l l e r number of s h e a r s a m p l e s . Lower a d h e s i v e l o a d i n g and s m a l l e r p a r a f o r m a l d e h y d e 1 28 c o n c e n t r a t i o n s t h a n had been used p r e v i o u s l y were f o u n d t o g i v e s i g n i f i c a n t l y b e t t e r r e s u l t s . In t h e b e s t s i t u a t i o n , w i t h a g l u e l i n e l o a d i n g of 1.94 g/100cm 2 and 0.2 g p a r a f o r m a l d e h y d e per 5.9 g o f a d h e s i v e , an a v e r a g e d r y s h e a r s t r e n g t h of 220 p s i w i t h 60% wood f a i l u r e was o b s e r v e d , but no wet s t r e n g t h was e v i d e n t . (3) Summary Q u a l i t a t i v e and q u a n t i t a t i v e t e s t i n g of a d h e s i v e f o r m u l a t i o n s b a s e d on t h e m i x t u r e o f o r g a n i c compounds p r o d u c e d from t h e c l e a v a g e of w e s t e r n hemlock bark t a n n i n s were done u s i n g s t a n d a r d t e c h n i q u e s . A l t h o u g h e a r l y r e s u l t s from t h e q u a l i t a t i v e t e s t i n g were p r o m i s i n g , t h e y c o u l d not be d u p l i c a t e d l a t e r q u a n t i t a t i v e l y . I t was f o u n d t h a t t h e q u a l i t y of t h e bark u s e d and i t s c o r r e s p o n d i n g a b i l i t y t o undergo t h e c l e a v a g e r e a c t i o n , d e g r a d e d r a p i d l y d u r i n g s t o r a g e . A d h e s i v e s made w i t h b a r k s t o r e d f o r more than two months d i d not have any wet s t r e n g t h a t a l l . A ssembly t i m e , m e t h y l o l a t i o n of low m o l e c u l a r w e i g h t p h e n o l i c s , p a r a f o r m a l d e h y d e c o n t e n t and a d h e s i v e l o a d i n g were f o u n d t o be f a c t o r s i m p o r t a n t i n d e t e r m i n i n g t h e s t r e n g t h of a bond made w i t h t h i s t y p e of b a r k - b a s e d a d h e s i v e . 129 CHAPTER V. SUMMARY Over t h e p a s t 35 y e a r s a g r e a t d e a l o f r e s e a r c h has been done w o r l d - w i d e on t h e p r o b l e m o f u s i n g t r e e b a r k t a n n i n s as s u b s t i t u t e s f o r t h e p e t r o l e u m d e r i v e d a d h e s i v e s w i d e l y u s e d i n t h e m a n u f a c t u r e of f o r e s t p r o d u c t s . In some s i t u a t i o n s , p a r t i c u l a r l y i n S o u t h A f r i c a w i t h w a t t l e t a n n i n s , t h e r e have been s u c c e s s f u l a p p l i c a t i o n s . In B r i t i s h C o l u m b i a , t h e t a n n i n s from w e s t e r n hemlock bark have a t t r a c t e d t h e most a t t e n t i o n . The p r o b l e m s f o u n d w i t h u s i n g t a n n i n from t h i s s p e c i e s as a d h e s i v e s , and from c o n i f e r s i n g e n e r a l , a r e : (1) Low bond s t r e n g t h due t o t h e h i g h a v e r a g e m o l e c u l a r w e i g h t of t h e b a r k t a n n i n s and r e l a t i v e l y few c r o s s l i n k i n g s i t e s . (2) O v e r l y h i g h r e a c t i v i t y w i t h f o r m a l d e h y d e making t h e p o l y m e r i z a t i o n r e a c t i o n s r a t h e r d i f f i c u l t t o c o n t r o l and r e s u l t i n g i n a s h o r t a d h e s i v e p o t - l i f e . (3) V a r i a b l e bark q u a l i t y , r e s u l t i n g i n v a r i a b l e bond s t r e n g t h s f o r a c o n i f e r - t a n n i n b a s e d a d h e s i v e . F o r w e s t e r n hemlock i n p a r t i c u l a r , t h e bond q u a l i t y seems t o depend on t h e age and p a s t h i s t o r y of t h e bark from w h i c h i t i s e x t r a c t e d . Some a p p r o a c h e s t a k e n by o t h e r w o r k e r s t o s o l v e t h e s e p r o b l e m s have been: (1) U l t r a f i l t r a t i o n t o i s o l a t e t h e optimum m o l e c u l a r w e i g h t range o f t h e t a n n i n s . (2) Breakdown of t h e t a n n i n p o l y m e r i n t o s u l p h i t e d lower m o l e c u l a r w e ight o l i g o m e r s and monomers. (3) U s i n g s p e c i a l t a n n i n i s o l a t i o n and a d h e s i v e f o r m u l a t i o n 1 30 t e c h n i q u e s such as slow f o r m a l d e h y d e - r e l e a s e a g e n t s , s p e c i a l i z e d e x t r a c t i o n t e c h n i q u e s and h i g h p r e s s -t e m p e r a t u r e s . The a p p r o a c h t o t h e p r o b l e m t a k e n h e r e was t o b r e a k down the t a n n i n i n t o s i m p l e r p h e n o l i c m o l e c u l e s t h a t would be e a s i e r t o u t i l i z e a s an a d h e s i v e b a s e . A r e a c t i o n was i n v e s t i g a t e d t h a t c l e a v e s c a t e c h i n (a model compound f o r c o n i f e r t a n n i n s ) i n t o c a t e c h o l and q u i n o l i n e d e r i v a t i v e s . T h i s r e a c t i o n c an a l s o be a p p l i e d t o w e s t e r n hemlock b a r k e x t r a c t s , i n w h i c h c a s e some p h e n o l i s p r o d u c e d as w e l l . The p r o p e r t i e s of c a t e c h o l and p h e n o l i n a d h e s i v e m i x t u r e s " w i t h f o r m a l d e h y d e a r e w e l l known. I f t h e s e p r o d u c t s were i s o l a t e d from t h e p r o d u c t m i x t u r e t h e y c o u l d be u s e d t o make e x c e l l e n t a d h e s i v e s . A f t e r d e v e l o p m e n t of a q u i c k GC-based a s s a y p r o c e d u r e f o r c a t e c h o l , t h e optimum r e a g e n t and c o n d i t i o n s f o r p r o d u c t i o n of c a t e c h o l from c a t e c h i n were d e t e r m i n e d t o be a s o l u t i o n of 30% ammonium s u l p h i t e i n c o n c e n t r a t e d ammonium h y d r o x i d e h e a t e d t o 175° C f o r 2 h o u r s . Under t h e s e c o n d i t i o n s a 35% m o l a r y i e l d of c a t e c h o l was o b t a i n e d . A mechanism f o r t h e c l e a v a g e r e a c t i o n of c a t e c h i n was p r o p o s e d p a r t i a l l y b ased on t h e s t r u c t u r e s o f an i n t e r m e d i a t e and two c a t e c h o l c o - p r o d u c t s . The compound 1 — (3,4 — d i h y d r o x y p h e n y l ) - 2 - h y d r o x y - 3 - ( 1 , 3 , 5 -t r i h y d r o x y p h e n y l ) p r o p a n e s u l p h o n i c a c i d was formed from a low t e m p e r a t u r e r e a c t i o n of c a t e c h i n w i t h ammonium s u l p h i t e . I f h e a t e d t o 175° C w i t h t h e ammonium s u l p h i t e r e a g e n t , t h i s compound r e a c t s f u r t h e r t o g i v e c a t e c h o l . The two c o - p r o d u c t s 131 3 - a m i n o - 5 - h y d r o x y - 7 - q u i n o l i n e s u l p h o n i c a c i d and 3 , 5 ~ d i a m i n o - 7 -q u i n o l i n e s u l p h o n i c a c i d . O t h e r i n f o r m a t i o n on t h e r e a c t i o n mechanism of c a t e c h i n came from t h e i d e n t i f i c a t i o n o f r e a c t i o n p r o d u c t s from r e l a t e d compounds s u c h as p h l o r o g l u c i n o l , d i h y d r o q u e r c e t i n and w a t t l e t a n n i n , o b t a i n e d under t h e same c o n d i t i o n s . The r e a c t i o n r e q u i r e m e n t s of h i g h t e m p e r a t u r e , h i g h c o n c e n t r a t i o n o f ammonia and t h e p r e s e n c e of s u l p h i t e i o n a r e t h e same as t h o s e needed f o r t h e B u c h e r e r r e a c t i o n , a c l a s s i c s u b s t i t u t i o n r e a c t i o n by w hich c e r t a i n h y d r o x y l a t e d a r o m a t i c compounds can be c o n v e r t e d t o a n i l i n e d e r i v a t i v e s and v i c e  v e r s a . An u n d e r s t a n d i n g of t h i s r e a c t i o n p r o v e d t o be c r i t i c a l i n u n d e r s t a n d i n g t h e c l e a v a g e o f c a t e c h i n . The r e a c t i o n mechanism e n v i s a g e d f o r t h e c l e a v a g e of c a t e c h i n i n t o c a t e c h o l i s summarized below (See F i g u r e 111-29). (1) O p e n i n g o f t h e c a t e c h i n C - r i n g t o g i v e t h e i s o l a t e d 2-s u l p h o n i c a c i d i n t e r m e d i a t e . (2) D i s p r o p o r t i o n a t i o n of t h e q u i n o n e - m e t h i d e i n e q u i l i b r i u m w i t h th e s u l p h o n i c a c i d t o g i v e two p r o d u c t s w i t h t h e same c a r b o n backbone but i n d i f f e r e n t o x i d a t i o n s t a t e s . (3) A m i n a t i o n of t h e p h l o r o g l u c i n o l i c A - r i n g of t h e h i g h e r o x i d a t i o n s t a t e p r o d u c t v i a t h e B u c h e r e r r e a c t i o n . (4) C l e a v a g e t o f o r m c a t e c h o l and a 9 - carbon q u i n o n e m e t h i d e by a mechanism r e l a t e d t o h e t e r o l y t i c f r a g m e n t a t i o n . (5) C y c l i z a t i o n t o form a p a r t i a l l y a r o m a t i c b i c y c l i c compound. (6) L o s s of b i s u l p h i t e t o g i v e t h e f u l l y a r o m a t i c q u i n o l i n e s t r u c t u r e . 1 3 2 A d h e s i v e f o r m u l a t i o n s b a s e d on t h e m i x t u r e of o r g a n i c compounds p r o d u c e d from t h e c l e a v a g e of w e s t e r n hemlock bark t a n n i n s were q u a l i t a t i v e l y and q u a n t i t a t i v e l y t e s t e d f o r s t r e n g t h u s i n g s t a n d a r d t e c h n i q u e s . A l t h o u g h e a r l y r e s u l t s from t h e q u a l i t a t i v e t e s t i n g were p r o m i s i n g , t h e y c o u l d not be d u p l i c a t e d l a t e r q u a n t i t a t i v e l y . T h i s was t h e r e s u l t of t h e q u a l i t y o f t h e bark u s e d and i t s a b i l i t y t o undergo t h e c l e a v a g e r e a c t i o n , d e g r a d i n g f a i r l y r a p i d l y d u r i n g s t o r a g e . A d h e s i v e s made w i t h b a r k s t o r e d f o r more t h a n two months d i d not have any wet s t r e n g t h a t a l l . Some f a c t o r s f o u n d t o be i m p o r t a n t i n d e t e r m i n i n g t h e s t r e n g t h of a bond made w i t h t h i s t y p e of b a r k -b a s e d a d h e s i v e were a s s e m b l y t i m e , m e t h y l o l a t i o n of low m o l e c u l a r w e i g h t p h e n o l i c s , p a r a f o r m a l d e h y d e c o n t e n t and a d h e s i v e l o a d i n g . The r e s u l t s of t h e b o n d i n g e x p e r i m e n t s were not as good as t h e y m i g h t have been. In r e t r o s p e c t , t h e s e poor bond s t r e n g t h s c o u l d have been f o r e s e e n . I t i s l i k e l y t h a t t h e c l e a v a g e r e a c t i o n i n t a n n i n s p r o c e e d s by t h e same mechanism as w i t h c a t e c h i n . I f t h i s i s t r u e , t h e r e s h o u l d be s u l p h o n a t i o n of t h e r e m a i n i n g t a n n i n a r o m a t i c r i n g s a f t e r t h e c a t e c h o l B - r i n g has been s p l i t o f f . The s u l p h o n i c a c i d g r o u p i s a s t r o n g e l e c t r o p h i 1 i c s u b s t i t u e n t , and on an a r o m a t i c r i n g would have a d e a c t i v a t i n g e f f e c t on e l e c t r o p h i l i c a r o m a t i c s u b s t i t u t i o n . T h i s means t h e s u b s t i t u t e d r i n g would be l e s s r e a c t i v e t o f o r m a l d e h y d e than might be e x p e c t e d . I f t h e a r o m a t i c r i n g i s a l s o a m i n a t e d and i n t h e z w i t t e r i o n form as was o b s e r v e d w i t h AHQSA, t h e m a t e r i a l w i l l be even l e s s r e a c t i v e , as t h e -NH 3+ 1 33 s u b s t i t u e n t has a v e r y s t r o n g d e a c t i v a t i n g e f f e c t . P r o b a b l y t h e bond s t r e n g t h t h a t was o b s e r v e d was o n l y due t o t h e f r e e c a t e c h o l , p h e n o l and u n r e a c t e d t a n n i n m o l e c u l e s . I t i s u n l i k e l y t h a t good bond s t r e n g t h s can be a c h i e v e d u s i n g t h e whole m i x t u r e of o r g a n i c compounds p r o d u c e d from t h e c l e a v a g e o f w e s t e r n hemlock bark t a n n i n s . The p o s s i b i l i t y s t i l l r e m a i n s of u s i n g o n l y t h e c a t e c h o l and p h e n o l p r o d u c e d by t h e r e a c t i o n a s an a d h e s i v e b a s e . These compounds can be i s o l a t e d v e r y e a s i l y from t h e r e a c t i o n m i x t u r e by s o l v e n t e x t r a c t i o n . However, a t t h e p r e s e n t s t a t e of d e v e l o p m e n t , t h e r e a c t i o n p r o b a b l y does not have a h i g h enough y i e l d t o make i t c o m m e r c i a l l y f e a s i b l e . B ased on t h e mechanism o f t h e c l e a v a g e r e a c t i o n p r o p o s e d , t h e r e a p p e a r s t o be two i m p o r t a n t f a c t o r s ' 1 i m i t i n g t h e p h e n o l i c y i e l d from b a r k t a n n i n . F i r s t , by t h e n a t u r e of t h e p r o d u c t s formed from c a t e c h i n , i t i s n e c e s s a r y t h a t t h e r e be an o x i d a t i o n s t e p i n t h e r e a c t i o n sequence l e a d i n g up t o t h e e l i m i n a t i o n of c a t e c h o l . The most l i k e l y o x i d i z i n g a g e n t i s a q u i n o n e m e t h i d e as d i s c u s s e d i n s e c t i o n I I I - C ( 3 ) . A f t e r t h e m e t h i d e has been r e d u c e d i t c o u l d not r e a r r a n g e f u r t h e r and e l i m i n a t e c a t e c h o l by t h e t y p e of mechanism d e s c r i b e d . T h i s c o u l d a c c o u n t f o r t h e y i e l d from c a t e c h i n b e i n g l e s s t h a n 50%; h a l f of t h e p o t e n t i a l c a t e c h o l - p r o d u c i n g m a t e r i a l i s not r e a c t i v e a f t e r b e i n g r e d u c e d . I t i s p o s s i b l e , t h a t i f a r e a g e n t c a p a b l e of p e r f o r m i n g t h i s o x i d a t i o n s t e p was added t o t h e r e a c t i o n m i x t u r e , t h e y i e l d of c a t e c h o l from c a t e c h i n ( o r t a n n i n ) c o u l d be d o u b l e d . The s e c o n d p r o b l e m c o n c e r n s t h e n a t u r e of t h e b a r k t a n n i n 1 34 m o l e c u l e . As d i s c u s s e d e a r l i e r , t h e t a n n i n p o l y m e r p r o b a b l y has > a r a n d o m l y - o r i e n t e d , g l o b u l a r c o n f i g u r a t i o n i n s o l u t i o n , w i t h s t r o n g i n t r a m o l e c u l a r h y d r o g e n - b o n d i n g and p e r h a p s some c o v a l e n t c r o s s l i n k i n g as w e l l . Not o n l y w i l l a c o n f o r m a t i o n of t h i s t y p e l i m i t a c c e s s i b i l i t y of t h e r e a g e n t s t o t h e i n t e r i o r of t h e m o l e c u l e , but t h e r o t a t i o n a l f r e e d o m ' o f some bonds would be s e v e r e l y l i m i t e d and may not a l l o w r e a c t i v e c e n t e r s t o a p p r o a c h c l o s e enough t o p e r m i t t h e c l e a v a g e r e a c t i o n t o o c c u r . I f t h e t a n n i n p o lymer c o u l d be b r o k e n down i n t o s m a l l e r u n i t s , t h e r e a c t i o n would p r o b a b l y go more r e a d i l y and t o a g r e a t e r e x t e n t . R e c e n t l y , Foo e t a l . (144) r e p o r t e d t h a t P i n u s t a e d a L. bark t a n n i n was c l e a v e d a t t h e i n t e r f l a v a n o i d bonds by NaHS0 3 when r e f l u x e d f o r 24 h o u r s i n w a t e r . A 20% y i e l d of monomeric s u l p h i t e d t a n n i n was r e p o r t e d . I f t h i s t y p e o f r e a c t i o n a l s o o c c u r s w i t h w e s t e r n hemlock b a r k t a n n i n s , p r e - r e a c t i o n of t h e t a n n i n w i t h NaHS0 3 b e f o r e a t t e m p t i n g t h e c l e a v a g e r e a c t i o n may improve t h e y i e l d of s i m p l e p h e n o l s . The c o m b i n a t i o n o f an added o x i d i z i n g a g e n t and p r e -c l e a v a g e of some i n t e r f l a v a n o i d bonds may b r i n g t h e y i e l d of s i m p l e p h e n o l s d e r i v e d from s o f t w o o d bark by t h i s r e a c t i o n t o c o m m e r c i a l l y a c c e p t a b l e l e v e l s . E x p e r i m e n t s i n v e s t i g a t i n g t h e s e a p p r o a c h e s were n o t done h e r e . They a r e a l o g i c a l ' s e c o n d p h ase' t o t h e p r e l i m i n a r y i n v e s t i g a t i o n s d i s c u s s e d " i n t h i s t h e s i s . 1 35 CHAPTER V I . EXPERIMENTAL VI-A. G e n e r a l I n f o r m a t i o n (1) S p e c t r o s c o p y and Chromatography I n f r a r e d (IR) s p e c t r a were o b t a i n e d u s i n g a P e r k i n E l m e r 681 I n f r a r e d S p e c t r o p h o t o m e t e r . Samples were p r e p a r e d e i t h e r a s a t h i n s o l i d f i l m on an A g C l p l a t e o r as a KBr p e l l e t . The p r o t o n n u c l e a r m a g n e t i c r e s o u r c e (P-NMR) s p e c t r a were t a k e n on V a r i a n A s s o c i a t e s s p e c t r o m e t i c models XL-100 or HA-100(100 MHz) and a B r u k e r WP-80 (80 MHz) i n s t r u m e n t s . DMSO-d6 (Sigma, 100% d e u t e r a t e d ) and a c e t o n e - d 6 (Sigma, 95% d e u t e r a t e d ) were t h e d e u t e r a t e d s o l v e n t s n o r m a l l y u s e d , w i t h t e t r a m e t h y l s i l a n e (TMS) as an i n t e r n a l s t a n d a r d . S i g n a l p o s i t i o n s a r e g i v e n i n p a r t s p e r m i l l i o n (ppm) d o w n f i e l d from t h e i n t e r n a l s t a n d a r d s i g n a l ( d e l t a ) . 1 3C-NMR s p e c t r a were d e t e r m i n e d on a V a r i a n CFT-20 s p e c t r o m e t e r . U l t r a v i o l e t (UV) a b s o r p t i o n s p e c t r a were o b t a i n e d on a Unicam SP8000 UV R e c o r d i n g S p e c t r o p h o t o m e t e r . Low r e s o l u t i o n mass s p e c t r o g r a m s were c a r r i e d o ut on a Varian/MAT CH4B mass s p e c t r o m e t e r w h i l e GC-MS work was done on a H e w l e t t P a c k a r d 5985B s y s t e m . The c a p i l l a r y column u s e d i n GC-MS a n a l y s i s c o n t a i n e d a SE-54 l i q u i d p h a s e . The components o f p r o d u c t m i x t u r e s a n a l y s e d by t h i s t e c h n i q u e were i d e n t i f i e d by use of a c o m p u t e r i z e d mass s p e c t r u m l i b r a r y s e a r c h r o u t i n e and c o n v e n t i o n a l a n a l y s i s of t h e i n d i v i d u a l mass s p e c t r u m . S p e c t r a a r e l i s t e d as m/e ( r e l a t i v e a b u n d a n c e ) . A n a l y t i c a l gas l i q u i d c h r o m a t o g r a p h y was done on a H e w l e t t P a c k a r d 7620A R e s e a r c h C h r o m a t o g r a p h e q u i p p e d w i t h a 2 f t . l o n g , 0.25 i n c h O.D. g l a s s column p a c k e d w i t h CSP-633 1 36 ( C h r o m a t o g r a p h i c S p e c i a l t i e s ) . I n t e g r a t i o n of p e a k s was p e r f o r m e d by an a t t a c h e d H e w l e t t P a c k a r d 3370B I n t e g r a t o r . An on-column i n j e c t i o n s y s t e m was us e d i n t h i s c a s e . T h i s s y s t e m was us e d f o r a n a l y s i s o f m i x t u r e s c o n t a i n i n g p o l a r compounds s u c h as p h e n o l s . F o r n o n - p o l a r compounds, a 6 f t . X 0.125 i n c h s t a i n l e s s s t e e l column c o n t a i n i n g 5% OV-17 on Chromosorb W was u s e d . A n a l y t i c a l t h i n - l a y e r c h r o m a t o g r a p h y (TLC) was c a r r i e d o ut on Whatman K5F p r e - c o a t e d s i l i c a g e l p l a t e s c o n t a i n i n g a f l u o r e s c e n t i n d i c a t o r . V i s u a l i z a t i o n was done by s t a i n i n g w i t h I 2 v a p o r or v i s u a l i z a t i o n w i t h s h o r t - w a v e l e n g t h u l t r a v i o l e t l i g h t . The 20 cm X 20 cm p l a t e s were n o r m a l l y c u t i n t o 4 cm X 10 cm p i e c e s f o r a n a l y t i c a l work. P r e p a r a t i v e TLC was done on f u l l - s i z e Whatman PLK5F p l a t e s . U n l e s s o t h e r w i s e n o t e d , t h e d e v e l o p i n g s o l v e n t s y s t e m was e t h y l a c e t a t e / i s o p r o p a n o l / w a t e r i n p r o p o r t i o n s of 50:25:11. S o l v e n t r a t i o s a r e volume t o volume. A l l s o l v e n t s f o r c h r o m a t o g r a p h i c o r r e a c t i o n medium a p p l i c a t i o n s were d i s t i l l e d b e f o r e u s e . E l e m e n t a l a n a l y s e s were done by C a n a d i a n M i c r o a n a l y t i c a l S e r v i c e s . (2) G e n e r a l Methods S m a l l p lywood p a n e l s were made w i t h an Elmes E n g i n e e r i n g Works 15 i n c h X 15 i n c h h o t p r e s s . The p a n e l s were c u t i n t o s t a n d a r d 1 i n c h X 3 i n c h s h e a r t e s t samples w i t h a 1 i n 2 t e s t a r e a . The s h e a r samples were c u t su c h t h a t i n h a l f of t h e t e s t 1 37 p i e c e s , t h e l a t h e c h e c k s were p u l l e d c l o s e d upon t e s t i n g w h i l e i n t h e o t h e r h a l f t h e l a t h e c h e c k s were p u l l e d open. M o i s t u r e c o n t e n t s (M.C.) a r e r e p o r t e d on a n e t b a s i s , e.g. MC=weight of H 2 0 / w e i g h t of H 2 0 + o v e n - d r y w e i g h t o f b a r k . E v a p o r a t i o n of s o l v e n t s was done u s i n g a r o t a r y e v a p o r a t o r w i t h a b a t h t e m p e r a t u r e of a b o u t 43° C M e l t i n g p o i n t s were d e t e r m i n e d u s i n g a F i s h e r - J o h n s M e l t i n g P o i n t A p p a r a t u s and a r e u n c o r r e c t e d . (3) M a t e r i a l s W e s t e r n hemlock b a r k was c o l l e c t e d on two o c c a s i o n s . On May 5, 1982, a p p r o x i m a t e l y 20 kg o f b a r k was c o l l e c t e d from two l o g s a b o u t 60 cm i n d i a m e t e r t h a t had been f e l l e d 10 d a y s p r e v i o u s l y a t t h e UBC R e s e a r c h F o r e s t , Haney, B.C.. A f t e r s t r i p p i n g from t h e l o g s , t h e bark was c o a r s e l y c hopped i n t o p i e c e s not e x c e e d i n g 25 cm 2 i n a r e a and l e t a i r - d r y f o r 72 h r s . No a t t e m p t was made t o s e p a r a t e i n n e r and o u t e r bark l a y e r s . The d r i e d b a r k was t h e n p a s s e d t h r o u g h a #2 W i l e y M i l l u s i n g a s c r e e n w i t h 5 mm o p e n i n g s . A f t e r f u r t h e r a i r - d r y i n g o v e r n i g h t , th e b a r k was g r o u n d i n a P a l l m a n g r i n d e r t o a b o u t 200 mesh. At t h i s p o i n t , t h e m o i s t u r e c o n t e n t was 10.87%. The g r o u n d w e s t e r n hemlock b a r k was s t o r e d i n a f r e e z e r a t -10° C. T h i s m a t e r i a l was u s e d i n t h e work d e s c r i b e d i n C h a p t e r s II and I I I . The s e c o n d b a t c h of w e s t e r n hemlock bark was c o l l e c t e d on M a r c h 13, 1983 from a 45 cm DBH t r e e t h a t had been blown down 1 38 two days p r e v i o u s l y a t t h e UBC R e s e a r c h F o r e s t . The 50 kg of ba r k was d r i e d and gro u n d i n t h e same manner as d e s c r i b e d above. A f t e r p r o c e s s i n g , t h e m o i s t u r e c o n t e n t of t h e g r o u n d bark was 17.5%. The b o n d i n g e x p e r i m e n t s i n C h a p t e r IV were done u s i n g t h i s m a t e r i a l . V e n e e r (0.1 i n c h e s t h i c k ) u s e d i n t h e b o n d i n g e x p e r i m e n t s had been p e e l e d a t F o r i n t e k Canada C o r p . from D o u g l a s f i r l o g s . The v e n e e r had a m o i s t u r e c o n t e n t o f 6% when u s e d . C a t e c h i n u s e d i n t h i s work was o b t a i n e d from Sigma and c o n t a i n e d two and one h a l f moles of water of c r y s t a l l i z a t i o n p e r mole of c a t e c h i n . V I - B . C h a p t e r II (1) A c e t y l a t e d C a t e c h o l A s s a y P r o c e d u r e One gram o f r e a c t i o n m i x t u r e c o n t a i n i n g c a t e c h o l was added t o 10 ml o f d i s t i l l e d w a ter a l o n g w i t h 1.00 ml o f p h l o r o g l u c i n o l s t a n d a r d s o l u t i o n (3.50 mg/ml i n w a t e r ) . The s o l u t i o n was t h e n e x t r a c t e d w i t h t h r e e 15 ml p o r t i o n s of d i e t h y l e t h e r . A f t e r d r y i n g w i t h M g S O „ , t h e combined e t h e r l a y e r s were f i l t e r e d and th e n e v a p o r a t e d i n an a i r s t r e a m . The r e s i d u e of c a t e c h o l and p h l o r o g l u c i n o l was r e d i s s o l v e d i n 3 ml of 1:1 p y r i d i n e / a c e t i c a n h y d r i d e and h e a t e d t o 60° C f o r 1 hour i n a water b a t h . A f t e r c o o l i n g , 10 ml of d i s t i l l e d water was added and t h e r e s u l t i n g s o l u t i o n e x t r a c t e d w i t h 40 ml of d i e t h y l e t h e r . The e t h e r l a y e r was washed by s h a k i n g w i t h c o n c e n t r a t e d aqueous NaHC0 3, f o l l o w e d 1 39 by two w a s h i n g s w i t h d i s t i l l e d w a t e r . T h i s s t e p removed any a c e t i c a c i d p r e s e n t , and most of t h e p y r i d i n e , from t h e e t h e r l a y e r . A f t e r d r y i n g w i t h MgSO u, t h e e t h e r was e v a p o r a t e d t o abo u t 2 ml, a p o r t i o n of w h i c h , (2 u l ) , was t h e n a n a l y s e d on a gas c h r o m a t o g r a p h u s i n g an 0V-17 column. The t e m p e r a t u r e p r o g ram u s e d was: T e m p e r a t u r e Time a t That Temp. H e a t i n g Rate t o Next Temp. 120° C 4 min. 30° C/min. 225° C 10 mins. 30° C/min. 290° C 10 m i n s . r e c o v e r t o 120° C The peaks i n t h e r e s u l t i n g chromatogram were i n t e g r a t e d and the r a t i o of t h e c a t e c h o l a c e t a t e t o p h l o r o g l u c i n o l a c e t a t e peak a r e a s d e t e r m i n e d . T h i s r a t i o was t h e n r e l a t e d t o a c o n c e n t r a t i o n of c a t e c h o l i n t h e o r i g i n a l r e a c t i o n s o l u t i o n by u s i n g a c a l i b r a t i o n e q u a t i o n . (2) U n d e r i v a t i z e d C a t e c h o l A s s a y P r o c e d u r e o - C r e s o l s t a n d a r d s o l u t i o n (0.500 ml, 10 mg/ml) was added t o 1.00 g of r e a c t i o n s o l u t i o n ( c o n t a i n i n g up t o 5 mg of c a t e c h o l ) . About 2 u l of t h e m i x t u r e was i n j e c t e d i n t o a gas c h r o m a t o g r a p h e q u i p p e d w i t h a CSP-633 g l a s s p r e p a r a t i v e column u s i n g on-column i n j e c t i o n . I n i t i a l T e m p e r a t u r e - 100° C 1 40 F i n a l T e m p e r a t u r e - 200° C H e a t i n g Rate - 20° C/min. Time At F i n a l Temp. - 10 min. A f t e r e a c h sample, water was i n j e c t e d u n t i l t h e r e s u l t i n g peak was s m a l l and of c o n s i s t e n t s i z e . When n e c e s s a r y , t h e column was m a n u a l l y c l e a n e d by w i p i n g o ut t h e n o n - v o l a t i l e d e p o s i t s c o n t a i n e d i n t h e f i r s t few c e n t i m e t e r s of column t u b i n g . The peaks i n t h e r e s u l t i n g c hromatogram were i n t e g r a t e d and t h e r a t i o o f t h e c a t e c h o l t o o - c r e s o l peak a r e a s r e l a t e d t o a w e i g h t of c a t e c h o l i n t h e one gram o f sample by u s i n g a c a l i b r a t i o n e q u a t i o n . (3) T y p i c a l P r o c e d u r e f o r I n v e s t i g a t i n g t h e Time-T e m p e r a t u r e - Y i e l d R e l a t i o n s h i p o f C a t e c h o l P r o d u c e d from C a t e c h i n C a t e c h i n (25.0 mg) was put i n ea c h o f t e n p y r e x i g n i t i o n t u b e s (ID-6mm, OD-l0mm, length-70mm, s o u r c e - F i s h e r ) . 1.00 grams of 30% ( N H u ) 2 S 0 3 i n c o n c e n t r a t e d ammonia s o l u t i o n was t h e n added t o e a c h t e s t - t u b e . The t u b e s were s e a l e d by h e a t i n g one end t o r e d h e a t i n a oxygen/methane f l a m e t h e n c r i m p i n g i t t o g e t h e r u s i n g pre-warmed f o r c e p s . The s e a l e d t u b e s were the n a n n e a l e d by h o l d i n g t h e m e l t e d end i n a methane f l a m e u n t i l a t h i c k c o a t i n g of c a r b o n was formed on t h e g l a s s . A f t e r a i r - c o o l i n g , t h e t u b e s were h e a t e d i n h o t t a p water and t h e n shaken u n t i l a l l t h e c a t e c h i n had d i s s o l v e d . The h e a t i n g t o r e a c t i o n 141 t e m p e r a t u r e was done i n a m o d i f i e d GC o v e n . T h i s a l l o w e d a c c u r a t e c o n t r o l o f t h e t e m p e r a t u r e , w h i l e t h e f o r c e d - a i r c i r c u l a t i o n r e s u l t e d i n r a p i d h e a t i n g of t h e r e a c t i o n t u b e s . F o r s p e c i f i c r e a c t i o n t i m e s a t t h e oven t e m p e r a t u r e , p a i r s of t u b e s were removed from t h e oven a t a p p r o p r i a t e i n t e r v a l s ( u s u a l l y 1 h o u r , 2 h o u r s , e t c . ) , l a b e l l e d and t h e n c o o l e d t o -5° C i n a f r e e z e r . N o r m a l l y , t h e r e a c t i o n t u b e s were s t o r e d o v e r n i g h t i n t h e f r e e z e r b e f o r e b e i n g a s s a y e d f o r c a t e c h o l c o n t e n t t h e nex t m o r n i n g . The c o n t e n t s o f t h e r e a c t i o n m i x t u r e s were a l s o examined by TLC. (4) C a t e c h o l Y i e l d of P r o d u c t s from t h e E x t r a c t i o n P r o c e d u r e of F r a s e r and Swan (32) Ground w e s t e r n hemlock b a r k (41.95 g, M.C.=12.9%, d r y wei g h t = 36.5 g) was s e q u e n t i a l l y e x t r a c t e d w i t h 200 ml e a c h of b e n z e n e / e t h a n o l ( 2 : 1 ) , e t h a n o l and water i n a S o x h l e t . I n d i v i d u a l e x t r a c t s o l u t i o n s were e v a p o r a t e d and d r i e d under vacuum w i t h P 2 0 5 o v e r n i g h t . A f t e r a i r - d r y i n g , t h e e x t r a c t e d b a r k was s t i r r e d w i t h 250 ml of 1% NaOH s o l u t i o n f o r 24 h o u r s . The s u s p e n s i o n was t h e n f i l t e r e d i n a Buchner f u n n e l t o g i v e 200 ml o f d a r k brown s o l u t i o n . The ba r k r e s i d u e was washed w i t h water and t h e d r i e d i n an oven (102° C) t o a c o n s t a n t w e i g h t of 23.51 g. The pH of t h e a l k a l i e x t r a c t s o l u t i o n was a d j u s t e d t o 3 and t h e s u s p e n s i o n f i l t e r e d t o g i v e a brown p r e c i p i t a t e . T h i s m a t e r i a l was washed t h r e e t i m e s by s u s p e n d i n g i n wat e r , 1 42 s e d i m e n t i n g t h e s u s p e n s i o n u s i n g a t a b l e - t o p c e n t r i f u g e and p o u r i n g o f f t h e wash w a t e r . The r e s i d u e was t h e n d r i e d o v e r n i g h t under vacuum. The e x t r a c t i o n t i m e s and y i e l d s a r e g i v e n i n T a b l e VI-1 w h i l e t h e major IR a b s o r b a n c e s (KBr p e l l e t ) a r e shown i n T a b l e V I - 2 . The t o t a l y i e l d of e x t r a c t s was 35.4%. E a c h e x t r a c t (30 mg) was t e s t e d f o r c a t e c h o l y i e l d u s i n g t h e same p r o c e d u r e as d e s c r i b e d above. S o l v e n t E x t r a c t i o n Time Weight Y i e l d P e r c e n t Y i e l d D e s c r i p t i o n B e n z e n e / E t h a n o l (2:1 ) 24 h r s . 7.051 19.3 P u r p l e S o l i d E t h a n o l 12 h r s . 2.743 7.5 P u r p l e S o l i d Water 72 h r s . 1 .572 4.3 P u r p l e S o l i d 1%NaOH 24 h r s . 1 .630 4.3 Brown S o l i d T a b l e V I - 1 . C o n d i t i o n s And Y i e l d Of P r o d u c t s From The E x t r a c t i o n P r o c e d u r e A c c o r d i n g To F r a s e r & Swan (32) (5) E x t r a c t i o n w i t h N e u t r a l S o l v e n t s and C a t e c h o l Y i e l d G r a n u l a t e d bark (49.38 g, MC=12.9%, d r y Weight=43.01 g ) , as d e s c r i b e d i n s e c t i o n V I - B . C h a p t e r 11(3) was s e q u e n t i a l l y e x t r a c t e d i n a S o x h l e t w i t h 200 ml e a c h of p e t r o l e u m e t h e r , 143 E x t r a c t M a j o r A b s o r b a n c e s B e n z e n e / E t n a n o l E t h a n o l Water 1% NaOH 3400,2900(weak),172 0(weak),1610,1510,1450 3400,1610,1515,1440 3400,1610,1515,1440 3400, 1-7 00 (weak) ,1610,1510 T a b l e V I - 2 . M a j o r IR A b s o r b a n c e s o f P r o d u c t s From t h e E x t r a c t i o n P r o c e d u r e A c c o r d i n g To F r a s e r And Swan (32) benzene, d i e t h y l e t h e r , a c e t o n e , e t h a n o l and w a t e r . The d r y w e i g h t of t h e b a r k a f t e r e x t r a c t i o n was 31.02 g, t o t a l y i e l d of e x t r a c t was 34.0%. The e x t r a c t s o l u t i o n s were e v a p o r a t e d t h e n put under vacuum o v e r P 2 0 5 o v e r n i g h t . The e x t r a c t i o n t i m e s , y i e l d s and a d e s c r i p t i o n of t h e s o l i d e x t r a c t a r e g i v e n i n T a b l e V I - 3 . IR s p e c t r a (KBr p e l l e t ) were t a k e n of e a c h e x t r a c t and a r e summarized i n T a b l e VT-4. E a c h e x t r a c t (30 mg) and 150 mg of t h e e x t r a c t e d bark were r e a c t e d w i t h ( N H 4 ) 2 S0 3/NH 3 f o r 4 h o u r s a t 175° C i n s e a l e d g l a s s t u b e s as d e s c r i b e d a b o v e . The y i e l d o f c a t e c h o l was t h e n d e t e r m i n e d u s i n g o - c r e s o l as a s t a n d a r d . (6) P r e p a r a t i o n of C a t e c h i n i c A c i d and R e a c t i o n w i t h 30% ( N H , ) 2 S 0 3 / N H 3 NaOH (0.25 g) was d i s s o l v e d i n 50 ml of water and t h e s o l u t i o n r e f l u x e d under a c o n t i n u o u s N 2 f l u s h . C a t e c h i n (0.5 g) was added and t h e s o l u t i o n r e f l u x e d f o r 45 m i n u t e s . The r e a c t i o n m i x t u r e was c o o l e d and t h e pH a d j u s t e d t o 4 w i t h d i l u t e So 1 vent E x t r a c t i o n T i m e ( h r s . ) Weight Y i e l d ( g ) P e r c e n t Y i e l d D e s c r i p t i o n of Dry E x t r a c t P e t . E t h e r 4 1.0572 2.46 Y e l l o w wax, m.p. - 25' C Benzene 6 0 .1556 0 . 36 Orange Gum D i e t h y l E t h e r 14 0.7482 1 . 74 P u r p l e s o l i d A c e t o n e 6 6.3262 14.71 P u r p l e s o l i d E t h a n o l 20 4.3968 10.71 B r o w n - P u r p l e S o l i d Water 20 1.7157 3 .99 B r o w n - P u r p l e S o l i d T a b l e V I - 3 . C o n d i t i o n s and Y i e l d s of P r o d u c t s From the N e u t r a l S o l v e n t E x t r a c t i o n S e r i e s 1 45 E x t r a c t M a j o r A b s o r b a n c e s P e t . E t h e r D i e t h y l E t h e r A c e t o n e E t h a n o l Water 2920,2850,1740,1510,1460,1370,1160 3400,1700(weak),1620,1510,1460,1360,1240 , 1 1 40 3400,1700(weak),1610,1515,1440,1360 3400,1610,1515,1440,1280 3400,1610,1515,1440,1280 T a b l e V I - 4 . M a j o r IR A b s o r b a n c e s Of P r o d u c t s From The N e u t r a l S o l v e n t E x t r a c t i o n S e r i e s HC1. Water was removed by e v a p o r a t i o n and t h e b r o w n i s h r e s i d u e d r i e d under vacuum o v e r n i g h t . The d r y s o l i d was t h e n t r i t u r a t e d w i t h d r y a c e t o n e and f i l t e r e d . TLC (40% m e t h a n o l i n CHC1 3) showed e s s e n t i a l l y one compound was p r e s e n t . IR (KBr p e l l e t ) -3 4 0 0 ( S ) , 1 7 0 0 ( S ) , 1 5 8 0 ( S ) , 1 5 0 0 ( S ) . NMR ( D 2 0 ) - 2 . l ( d , l , D , 2 . 7 ( d d d , 1 ) , 3 . 1 ( d d , 1 ) , 3.2(m,2), 4.5(m,1), 6.8(m,2). The p r e p a r e d c a t e c h i n i c a c i d (30 mg) was s e a l e d i n a g l a s s t u b e w i t h 1 g of 30% ( N H „ ) 2 S 0 3 / N H 3 and h e a t e d f o r 2 h o u r s a t 175° C. No c a t e c h o l was o b s e r v e d among t h e r e a c t i o n p r o d u c t s examined by TLC. (7) Maximum Y i e l d of C a t e c h o l from W e s t e r n Hemlock Bark Ten grams o f f r e s h l y c o l l e c t e d , f i n e l y g r o u n d , w e s t e r n hemlock b a r k ( t h e s e c o n d b a t c h d e s c r i b e d i n V I - A ( 3 ) , M.C.=11.92%, Dry Weight=8.81g) was h e a t e d w i t h 9 g o f ( N H „ ) 2 S 0 3 and 21 ml of c o n c e n t r a t e d NH aOH i n a s t a i n l e s s s t e e l r e a c t i o n 1 46 v e s s e l a t 175° C f o r 4 h o u r s . The r e s u l t i n g s u s p e n s i o n was f i l t e r e d t h r o u g h Buchner f u n n e l and t h e b a r k r e s i d u e washed w i t h t h r e e 25 ml p o r t i o n s of water t o g i v e 4.68 g of o v e n - d r i e d e x t r a c t e d b a r k . The aqueous s o l u t i o n s were combined, and e x t r a c t e d t h r e e t i m e s w i t h 100 ml of d i e t h y l e t h e r . A f t e r d r y i n g o v e r MgSO a, t h e combined e t h e r l a y e r s were e v a p o r a t e d , t h e n r e d i s s o l v e d i n water t o a volume of 10.00 ml. An a s s a y of t h i s s o l u t i o n f o r c a t e c h o l ( u n d e r i v a t i z e d p r o c e d u r e ) showed t h a t 98 mg of c a t e c h o l had been p r o d u c e d i n t h i s r e a c t i o n . V I - C . C h a p t e r I I I (1) I s o l a t i o n of 1 - ( 3 , 4 - D i h y d r o x y p h e n y l ) - 2 - h y d r o x y -3 - ( 1 , 3 , 5 - t r i h y d r o x y p h e n y l ) p r o p a n e s u l p h o n i c Ac i d C a t e c h i n (125 mg) was d i s s o l v e d i n 7 ml of water a l o n g w i t h 3 g o f ( N H 4 ) 2 S 0 3 . The s o l u t i o n was put i n t o a s c r e w t o p v i a l w i t h a t e f l o n s e a l i n t h e c a p , and h e a t e d t o 60° C i n a water b a t h . A f t e r 24 h o u r s , TLC showed one main p r o d u c t formed, and no c a t e c h i n p r e s e n t . M e t h a n o l (10 ml) was added w i t h s t i r r i n g t o t h e aqueous s o l u t i o n , t h e n t h e p r e c i p i t a t e d ( N H „ ) 2 S 0 3 f i l t e r e d o u t . The f i l t r a t e was e v a p o r a t e d , and t r i t u r a t e d w i t h m e t h a n o l . A f t e r f i l t r a t i o n and e v a p o r a t i o n of t h e f i l t r a t e , 100 mg of a w h i t e amorphous s o l i d was o b t a i n e d . The main component (60 mg) was i s o l a t e d by p r e p a r a t i v e TLC (4 p l a t e s , s o l v e n t s y s t e m - 75:25:7 e t h a n o l / C H C l 3 / H 2 0 ) . IR (KBr p e l l e t ) - 3 2 5 0 ( s ) , 1 47 1615(m), 1520(m), 1450(m), 1 1 4 5 ( s ) , 1 0 3 0 ( S ) , 650(m). NMR ( D 2 0 ) - 6.9(m,3), 6 . 8 5 ( s , 2 ) , 4.5(m,1), 3 . 9 ( d , 1 ) , 2 . 6 ( d , 2 ) . T h i s compound was i d e n t i c a l by IR and TLC a n a l y s i s t o t h e p r o d u c t p r o d u c e d by t h e r e a c t i o n o f c a t e c h i n w i t h NaHS0 3, p r e p a r e d and i s o l a t e d by t h e methods d e s c r i b e d above. (2) The R e a c t i o n of 1 - ( 3 , 4 - D i h y d r o x y p h e n y 1 ) - 2 -h y d r o x y - ( 1 , 3 , 5 - t r i h y d r o x y p h e n y l ) p r o p a n e s u l p h o n i c A c i d w i t h ( N H a ) 2 S 0 3 In Ammonia S o l u t i o n a t H i g h T e m p e r a t u r e s A s o l u t i o n of c a t e c h i n and ( N H 4 ) 2 S 0 3 i n c o n c e n t r a t e d N H „ O H was p r e p a r e d as d e s c r i b e d i n t h e p r e v i o u s s e c t i o n . A f t e r t h e r e a c t i o n a t 60° C, a p o r t i o n of t h e s o l u t i o n was r e s e a l e d i n a p y r e x i g n i t i o n t u b e and h e a t e d t o 175° C f o r two h o u r s . A n a l y t i c a l TLC showed the p r e s e n c e of t h e same p r o d u c t s ( i n c l u d i n g c a t e c h o l ) t h a t were o b s e r v e d from t h e d i r e c t r e a c t i o n of c a t e c h i n under t h e s e h i g h t e m p e r a t u r e c o n d i t i o n s . No a s s a y f o r c a t e c h o l y i e l d was done. (3) I s o l a t i o n of C a t e c h o l and 3-Amino-5-hydroxy-7-q u i n o l i n e s u l p h o n i c A c i d C a t e c h i n (4 g) was d i s s o l v e d i n 28 g of c o n c e n t r a t e d NH 4OH a l o n g w i t h 12 g of ( N H 4 ) 2 S 0 3 . The s o l u t i o n was s e a l e d i n a s t a i n l e s s s t e e l r e a c t i o n v e s s e l e q u i p p e d w i t h a p r e s s u r e gauge 1 48 and v a l v e . The r e a c t i o n v e s s e l was h e a t e d by p l a c i n g i n a t h e r m o s t a t i c a l l y c o n t r o l l e d g l y c e r i n b a t h s e t a t 175° C f o r 2 h o u r s . A f t e r c o o l i n g , t h e c l e a r , o r a n g e - c o l o r e d s o l u t i o n was e x t r a c t e d w i t h t h r e e 100 ml p o r t i o n s o f d i e t h y l e t h e r . The o r g a n i c l a y e r s were combined, d r i e d w i t h MgSO t t, t h e n e v a p o r a t e d t o g i v e 600 mg o f a r e s i d u e showing e s s e n t i a l l y one s p o t on a TLC p l a t e . T h i s m a t e r i a l was r e c r y s t a l l i z e d f r o m benzene and d r i e d under vacuum t o g i v e 454 mg of c a t e c h o l (35% m o l a r y i e l d ) . NMR (CDC1 3) - 6 . 4 7 ( s , 4 ) , 4 . 6 2 ( s , b r o a d , 2 ) . IR (KBr p e l l e t ) -3 4 5 0 ( s ) , 3 3 3 0 ( s ) , 1615(m), I600(m), 1 5 1 0 ( S ) , 1470(m), 1 3 6 0 ( s ) , I 2 5 0 ( s ) , 1 1 9 0 ( S ) , 1 0 9 5 ( S ) , 7 4 0 ( s ) . M.P. - 103° C. The i d e n t i t y was c o n f i r m e d by m e a s u r i n g t h e mixed m e l t i n g p o i n t w i t h a u t h e n t i c r e c r y s t a l l i z e d c a t e c h o l . T h e r e was no m e l t i n g p o i n t d e p r e s s i o n . M e t h a n o l (100 ml) was s t i r r e d i n t o t h e aqueous l a y e r . The p r e c i p i t a t e d ammonium s u l p h i t e was f i l t e r e d o u t , and t h e s o l u t i o n e v a p o r a t e d t o a s m a l l volume. The m e t h a n o l a d d i t i o n , f i l t r a t i o n and e v a p o r a t i o n was r e p e a t e d t w i c e more. TLC a n a l y s i s of t h e p r o d u c t (50:25:11, EtOAc/EtOH/H 20) showed a t l e a s t 5 d i f f e r e n t compounds were p r e s e n t . Two of t h e s p o t s were much more i n t e n s e than t h e o t h e r ( R f ' s - 0.57, 0.35). The o r g a n i c m a t e r i a l was d i s s o l v e d i n t h e minimum amount of water p o s s i b l e and d i v i d e d i n t o 4 p o r t i o n s . E a c h p o r t i o n was i n d i v i d u a l l y a p p l i e d t o a column made of 100 ml df A m b e r l i t e IR-120 i o n exchange r e s i n ( H + f o r m ) , and e l u t e d w i t h d i s t i l l e d w a t e r . S e v e r a l f r a c t i o n s were c o l l e c t e d and t h e s i m i l a r f r a c t i o n s from th e f o u r d i f f e r e n t e l u t i o n s c o m b i n e d . Compounds 1 49 w i t h a TLC Rf g r e a t e r t h a n 0.57 (TLC s o l v e n t s y s t e m d e f i n e d above) p a s s e d t h r o u g h t h e column f r e e l y and composed t h e o r g a n i c m a t e r i a l i n t h e f i r s t f r a c t i o n s c o l l e c t e d . The major component a t Rf=0.57 p a s s e d t h r o u g h t h e column s l o w l y , and a f t e r t h e few i n i t i a l h i g h l y c o l o r e d f r a c t i o n s a c l e a r , y e l l o w e l u a n t c o n t a i n i n g o n l y t h i s compound was o b t a i n e d . D i s t i l l e d water was c o n t i n u a l l y f l u s h e d t h r o u g h t h e column u n t i l t h e r e s u l t i n g s o l u t i o n was v e r y l i g h t l y c o l o r e d . The volume of e l u a n t s c o n t a i n i n g t h i s compound from t h e f o u r e l u a n t s e r i e s was about 3 l i t e r s . The compounds w i t h an Rf<0.57, i n c l u d i n g t h e major component a t Rf=0.35, were r e t a i n e d on t h e i o n - e x c h a n g e r e s i n , and c o u l d not be removed by e l u t i o n w i t h w a t e r . The t h r e e l i t e r s of s o l u t i o n c o n t a i n i n g t h e i s o l a t e d compound was e v a p o r a t e d t o g i v e a y e l l o w - o r a n g e amorphous s o l i d . R e c r y s t a l l i z a t i o n of t h e s o l i d from m e t h a n o l / w a t e r gave s m a l l n e e d l e - l i k e c r y s t a l s of t h e p u r e compound. IR (KBr p e l l e t ) - 3440(m), 3 3 5 0 ( s ) , I640(m), 1 6 l 5 ( m ) , 1 5 8 5 ( s ) , 1 5 7 0 ( s ) , 1 4 0 0 ( s ) , 1 2 9 5 ( s ) , 1260(m), 1 1 9 0 ( S ) , 1 0 4 0 ( S ) , 850(m), 6 4 0 ( s ) . NMR (DMSO) - 1 1 . 2 3 ( s , 1 , b r o a d , l a b i l e ) , 8.68(d,1,J=1.3 H z ) , 8.14(d,1,J=1.3 H z ) , 7 . 7 1 ( S , 1 ) , 7 . 3 0 ( S , 1 ) . UV ( H 2 0 ) - a b s o r b a n c e maxima a t 223 nm and 263 nm. T h e r e i s a b a t h o c h r o m i c s h i f t of b o t h a b s o r b a n c e s upon a d d i t i o n of a c i d or b a s e . MS - 1 4 9 ( 1 ) , 8 6 ( 4 . 6 ) , 8 5 ( 2 . 9 ) , 8 4 ( 9 0 ) , 6 8 ( 4 . 7 ) , 6 7 ( 2 . 0 ) , 6 6 ( 1 0 0 ) . 1 3C-NMR (DMSO-d6) - 162, 160, 152, 144, 140, 130, 126, 115, 113. E l e m e n t a l A n a l y s i s - f o u n d : C-43.11, H-3.87, N-10.87, O-30.91, 1 50 S-11.57. C a l c u l a t e d f o r C 9 H 1 0 N 2 0 5 S (MW=258): C-41.86, H-3.87, N-10.85, 0-31.01, S-12.40. T i t r a t i o n w i t h 0.0260 N NaOH showed a pKa a t pH 3.3 and a pKb a t pH 7.5. The m o l e c u l a r w e i g h t c a l c u l a t e d from t h e t i t r a t i o n d a t a was 247 g/m. C r y s t a l s f o r x - r a y a n a l y s i s o f t h i s compound were formed by d i s s o l v i n g 50 mg of t h e p u r i f i e d c r y s t a l l i z e d compound i n 50 ml of w a t e r , and t h e n s e e d i n g w i t h s m a l l c r y s t a l s p r e v i o u s l y s e l e c t e d f o r good form u s i n g a m i c r o s c o p e . The s o l u t i o n was c o n t a i n e d i n a 100ml E r l e n m e y e r f l a s k , p r o t e c t e d from t h e l i g h t by p l a c i n g i n an aluminum f o i l t u n n e l . A l o w - v e l o c i t y n i t r o g e n s t r e a m was i n t r o d u c e d from one end t o m a i n t a i n gas c i r c u l a t i o n w i t h i n t h e t u n n e l and i n d u c e a slow r a t e o f e v a p o r a t i o n . A f t e r two weeks t h e c r y s t a l s were f i l t e r e d o u t and washed w i t h c o l d d i s t i l l e d w a t e r . X-Ray c r y s t a l l o g r a p h i c a n a l y s i s was done a t th e Department o f C h e m i s t r y , UBC. (4) A c e t y l a t i o n of 3-Amino-5-hydroxy-7-q u i n o l i n e s u l p h o n i c A c i d The i s o l a t e d s u l p h o n i c a c i d (200 mg) was a c e t y l a t e d by d i s s o l v i n g i n 10 ml of 4:1 a c e t i c a n h y d r i d e / p y r i d i n e , and l e a v i n g o v e r n i g h t a t room t e m p e r a t u r e . M e t h a n o l was added w i t h c o o l i n g , u n t i l no more h e a t was g e n e r a t e d . The s o l u t i o n was t h e n s t i r r e d w i t h a d d i t i o n a l m e t h a n o l f o r an h o u r . A f t e r e v a p o r a t i o n of t h e m e t h y l a c e t a t e , t h e v i s c o u s r e s i d u e was put 151 under vacuum o v e r n i g h t t o remove t h e r e m a i n i n g p y r i d i n e . 190 mg of t h e r e s u l t i n g s o l i d was p u r i f i e d by p r e p a r a t i v e TLC on f o u r p l a t e s . The main component a t Rf=0.5l was i s o l a t e d . IR - 3 4 5 0 ( s ) , 1 7 6 5 ( S ) , 1 6 7 0 ( s ) , 1 6 l 0 ( m ) , 1 5 5 5 ( S ) , 1460(m), 1375(m), I280(m), 1 1 9 0 ( V S ) , 1 1 0 0 ( s ) , 1 0 5 0 ( s ) , 6 5 0 ( s ) . NMR - 1 0 . 5 5 ( S , 1 ) , 9.05(d,1,J=1.3 H z ) , 8.58(d,1,J=1.3 H z ) , 8 . 1 3 ( S , 1 ) , 7 . 6 2 ( S , 1 ) , 2.4.6(5,3), 2 . 1 8 ( S , 3 ) . (5) I s o l a t i o n o f 3 , 5 - D i a m i n o - 7 - q u i n o l i n e s u l p h o n i c Ac i d The o r g a n i c p r o d u c t s from t h e r e a c t i o n of 1 g o f c a t e c h i n w i t h 3 g of ( N H « ) 2 S 0 3 i n 7 ml of c o n c e n t r a t e d N H „ O H a t 175° C, were p r e p a r e d and i s o l a t e d i n t h e manner d e s c r i b e d i n V I - C . C h a p t e r 1 1 1 ( 2 ) . The p r o d u c t m i x t u r e (160 mg) was s e p a r a t e d on 4 p r e p a r a t i v e TLC p l a t e s . The bands c o n t a i n i n g t h e major component w i t h an Rf=0.35 were c o l l e c t e d . NMR - 8.36(d,1,J=1.4 H z ) , 7 . 3 6 ( S , 1 ) , 7.29(d,1,J=1.4 H z ) , 6 . 9 4 ( s , 1 ) . IR - 3 4 1 5 ( S ) , 3 3 6 0 ( s ) , 1 6 3 0 ( s ) , 1580(m), 1460(m), 1400(m), 1 1 9 0 ( s ) , 1 0 5 0 ( S ) , 6 5 0 ( s ) . 1 52 (6) R e a c t i o n o f P h l o r o g l u c i n o l w i t h ( N H „ ) 2 S 0 3 / N H 3 P h l o r o g l u c i n o l (2 g, r e c r y s t a l l i z e d from w a t e r ) was d i s s o l v e d w i t h ( N H „ ) 2 S 0 3 (6 g) i n 14 ml o f c o n c e n t r a t e d ammonia. The s o l u t i o n was s e a l e d i n a s t a i n l e s s s t e e l r e a c t i o n v e s s e l , and h e a t e d t o 175° C i n a g l y c e r i n b a t h f o r 2 h o u r s . A f t e r c o o l i n g , m e t h a n o l (100 ml) was added, and t h e p r e c i p i t a t e d s a l t f i l t e r e d o u t . The f i l t r a t e was e v a p o r a t e d t o d r y n e s s , t h e n t r i t u r a t e d w i t h m e t h a n o l . A f t e r f i l t e r i n g , t h e s o l u t i o n was e v a p o r a t e d , and t h e r e s u l t i n g r e s i d u e d r i e d under vacuum o v e r P 2 0 5 f o r 5 h o u r s t o g i v e 1.56 g of p r o d u c t . T h i s m a t e r i a l was a c e t y l a t e d by r e a c t i o n a t room t e m p e r a t u r e o v e r n i g h t w i t h 40 ml of 1:1 a c e t i c a n h y d r i d e / p y r i d i n e . U n r e a c t e d a c e t i c a n h y d r i d e was d e s t r o y e d by t h e a d d i t i o n o f e x c e s s m e t h a n o l , and t h e r e s u l t i n g s o l u t i o n was e v a p o r a t e d t o a s m a l l volume. Water and d i e t h y l e t h e r (50 ml each) were added. The e t h e r l a y e r was s e p a r a t e d , and washed w i t h s e v e r a l p o r t i o n s of w a t e r . The o r g a n i c l a y e r was d r i e d w i t h MgSO u and e v a p o r a t e d t o g i v e a w h i t e amorphous r e s i d u e . The m a t e r i a l (200 mg) was a n a l y z e d by s e p a r a t i o n on f o u r p r e p a r a t i v e TLC p l a t e s ( 9 : 1 , m e t h a n o l / c h l o r o f o r m ) . The t h r e e main bands were c o l l e c t e d and c h a r a c t e r i z e d . 1 , 3 , 5 - T r i a m i n o b e n z e n e t r i a c e t a t e (Rf=0.55, y i e l d = 5 4 . 3 mg). IR (KBr p e l l e t ) - 3 4 4 0 ( s ) , 3 3 1 0 ( S ) , 3 2 6 0 ( s ) , 1 6 6 0 ( s ) , 1610(s) , 1 5 6 0 ( S ) , 1 4 5 0 ( s ) , 1365(m), 1 2 8 5 ( s ) , 860(m). NMR (DMSO)-9 . 9 3 ( s , 3 ) , 7 . 6 2 ( s , 3 ) , 2 . 0 5 ( s , 9 ) . MS - 249, 207, 165, 123, 95, 59, 43. 1 - H y d r o x y - 3 , 5 - d i a m i n o b e n z e n e t r i a c e t a t e ( R f - 0 . 6 4 , 1 53 y i e l d = 1 1 . 2 mg). IR (KBr p e l l e t ) - 3450(m), 3260(m), 1755(m), 1 6 5 5 ( s ) , 1 6 1 0 ( s ) , 1 5 6 0 ( S ) , 1460(m), 1 4 2 0 ( s ) , 1365(m), 1275(s) 1 2 1 0 ( s ) . The l a s t component i s o l a t e d a p p e a r e d t o be i n c o m p l e t e l y a c e t y l a t e d , p r o b a b l y 1 , 3 , 5 - t r i a m i n o b e n z e n e d i a c e t a t e (Rf=0.32, y i e l d = 10.1 mg). IR (KBr p e l l e t ) - 3430(m), 3300(m), 1665(m), 1 6 1 0 ( s ) , 1 5 5 0 ( S ) , 1440(m), 1280(m), 1!95(m), 840(m). (7) R e a c t i o n of C a t e c h o l w i t h ( N H a ) 2 S 0 3 / N H 3 The r e a c t i o n p r o d u c t s of c a t e c h o l (1 g) w i t h 3 g o f ( N H f t ) 2 S 0 3 i n 7 g of c o n c e n t r a t e d N H „ O H were p r e p a r e d , a c e t y l a t e d and i s o l a t e d by t h e p r o c e d u r e o u t l i n e d i n s e c t i o n V I - C . C h a p t e r 1 1 1 ( 5 ) . The s i n g l e p r o d u c t o b t a i n e d was f o u n d t o be i n d i s t i n g u i s h a b l e from a u t h e n t i c 1, 2 - d i h y d r o x y b e n z e n e d i a c e t a t e when examined by a n a l y t i c a l TLC, GC (SE-30 c o l u m n ) ( s e p a r a t e and c o - i n j e c t i o n ) and mixed m e l t i n g p o i n t . (8) R e a c t i o n of R e s o r c i n o l w i t h ( N H 4 ) 2 S 0 3 / N H 3 The r e a c t i o n p r o d u c t s of r e s o r c i n o l (1 g) w i t h 3 g of ( N H a ) 2 S 0 3 i n 7 g of c o n c e n t r a t e d (NH4)OH were p r e p a r e d and a c e t y l a t e d by t h e p r o c e d u r e o u t l i n e d i n s e c t i o n V I - C . C h a p t e r I V ( 5 ) . The p r o d u c t m i x t u r e was t h e n a n a l y s e d by GC-MS. The 1 54 f o l l o w i n g compounds were i d e n t i f i e d by use of a c o m p u t e r i z e d mass s p e c t r u m l i b r a r y s e a r c h r o u t i n e and e x a m i n a t i o n of t h e i n d i v i d u a l mass s p e c t r a . 1 , 3 - D i h y d r o x y b e n z e n e d i a c e t a t e (major component) - MS -194(4) , 1 5 2 ( 1 6 ) , 110(100), 4 3 ( 6 1 ) . 1-Amino-3-hydroxybenzene d i a c e t a t e (major component) - MS -19 3 ( 6 ) , 1 5 1 ( 2 8 ) , 109(100), 8 1 ( 6 ) , 8 0 ( 8 ) , 4 3 ( 6 1 ) . 1,3-Diaminobenzene d i a c e t a t e (minor component) MS 192 ( 2 1 ) , 1 5 0 ( 3 0 ) , 1 4 9 ( 4 4 ) , 108(100), 8 1 ( 1 1 ) , 8 0 ( 1 7 ) , 4 3 ( 7 1 ) . (9) R e a c t i o n of W a t t l e Bark E x t r a c t w i t h (NH«) 2 SO 3 /NH 3. T h r e e grams of s p r a y - d r i e d w a t t l e b a r k e x t r a c t ( T a n n i n s and C h e m i c a l s I n c . ) was combined w i t h ( N H u ) 2 S 0 3 (6 g) and 14 g of c o n c e n t r a t e d N H„OH i n a s t a i n l e s s s t e e l r e a c t i o n v e s s e l w hich was t h e n h e a t e d t o 175° C f o r 2 h o u r s . The r e s u l t i n g s o l u t i o n was e x t r a c t e d t h r e e t i m e s w i t h 100 ml p o r t i o n s of d i e t h y l e t h e r . The o r g a n i c l a y e r s were combined, d r i e d w i t h MgSO a and e v a p o r a t e d . A c e t y l a t i o n was t h e n p e r f o r m e d w i t h 50 ml of 1:1 a c e t i c a n h y d r i d e / p y r i d i n e f o r 4 h r s . a t 50° C. E x c e s s a c e t i c a n h y d r i d e was d e s t r o y e d by a d d i n g m e t h a n o l . Water and d i e t h y l e t h e r (50 ml each) were t h e n added, shaken, and t h e o r g a n i c l a y e r i s o l a t e d . A f t e r e v a p o r a t i o n , t h e r e s u l t i n g r e s i d u e was a n a l y s e d by GC-MS. The p o s i t i o n s of t h e GC peaks were compared t o t h o s e of t h e compounds o b t a i n e d from r e s o r c i n o l t o d e t e r m i n e 1 55 s u b s t i t u t i o n p a t t e r n s . The i m p o r t a n t components i d e n t i f i e d a r e l i s t e d below. 1.2- d i h y d r o x y b e n z e n e d i a c e t a t e (major component) MS 1 9 4 ( 2 ) , 1 5 2 ( 1 8 ) , 110(100), 8 1 ( 4 ) , 6 4 ( 2 ) , 5 2 ( 6 ) , 4 3 ( 6 2 ) . 1.3- d i h y d r o x y b e n z e n e d i a c e t a t e (major component) - MS -1 9 4 ( 4 ) , 1 5 2 ( 1 5 ) , 110(100), 8 1 ( 3 ) , 8 0 ( 3 ) , 4 3 ( 6 3 ) . 2 , 6 - d i m e t h o x y p h e n o l a c e t a t e (minor component) MS 1 9 6 ( 5 ) , 1 5 4 ( 1 0 0 ) , 139(28), 1 1 1 ( 9 ) , 110(9),. 9 5 ( 8 ) , 9 3 ( 1 1 ) , 6 5 ( 9 ) , 4 3 ( 3 6 ) . 1-amino-3-hydroxybenzene d i a c e t a t e (major component) - MS -1 9 3 ( 5 ) , 1 5 1 ( 2 5 ) , 109(100), 8 1 ( 6 ) , 8 0 ( 8 ) , 4 3 ( 6 4 ) . 1,3-diaminobenzene d i a c e t a t e (minor component) MS 1 9 2 ( 2 2 ) , 1 5 0 ( 3 0 ) , 149(45), 1 0 8 ( 1 0 0 ) , 81(10 ) , 8 0 ( 1 6 ) , 7 7 ( 1 6 ) , 5 7 ( 1 3 ) , 4 3 ( 6 8 ) . (10), R e a c t i o n o f D i h y d r o q u e r c e t i n w i t h ( N H U ) 2 S 0 3 / N H 3 The r e a c t i o n p r o d u c t s of d i h y d r o q u e r c e t i n (200 mg) w i t h 1.2 g of ( N H a ) 2 S 0 3 i n c o n c e n t r a t e d N H„OH (2.8 ml) were p r e p a r e d , a c e t y l a t e d and i s o l a t e d by t h e p r o c e d u r e o u t l i n e d i n s e c t i o n V I -C. C h a p t e r 1 1 1 ( 8 ) , e x c e p t t h a t c h l o r o f o r m was u s e d f o r t h e i n i t i a l e x t r a c t i o n of o r g a n i c s from t h e r e a c t i o n s o l u t i o n . I n i t i a l TLC a n a l y s i s of t h e p r o d u c t s (9:1, c h l o r o f o r m / m e t h a n o l ) i n d i c a t e d t h a t t h e r e was no c a t e c h o l d i a c e t a t e p r e s e n t , a l t h o u g h a s p o t t h a t c o u l d have been due t o 1, 3, 5 - t r i a m i n o b e n z e n e t r i a c e t a t e was o b s e r v e d . GC a n a l y s i s (Carbowax 20M on 1 56 Chromosorb W) c o n f i r m e d t h e a b s e n c e o f t h e c a t e c h o l d e r i v a t i v e . C o - i n j e c t i o n of t h e r e a c t i o n p r o d u c t w i t h a u t h e n t i c t r i a m i n o b e n z e n e t r i a c e t a t e showed j u s t one peak. The major i s o l a t a b l e p r o d u c t from d i h y d r o q u e r c e t i n formed by t h i s r e a c t i o n and workup was 1,3,5 - t r i a m i n o b e n z e n e t r i a c e t a t e . (11) R e a c t i o n of P r o t o c a t e c h u i c A c i d w i t h ( N H , ) 2 S O 3 / N H 3 P r o t o c a t e c h u i c a c i d (20 mg) was s e a l e d i n an i g n i t i o n t u b e w i t h 300 mg of ( N H , ) 2 S 0 3 and 0.7 ml of c o n c e n t r a t e d NH,OH. The tu b e was h e a t e d i n a oven a t 175° C f o r two h o u r s . TLC a n a l y s i s o f t h e s o l u t i o n i n d i c a t e d t h e p r e s e n c e of c a t e c h o l . o - C r e s o l s t a n d a r d s o l u t i o n was added, and t h e amount of c a t e c h o l p r e s e n t a s s a y e d by t h e p r o c e d u r e o u t l i n e d i n s e c t i o n V I-B. C h a p t e r 1 1 ( 2 ) . The f o r m a t i o n o f c a t e c h o l was c o n f i r m e d by c o - i n j e c t i o n of a u t h e n t i c c a t e c h o l w i t h t h e r e a c t i o n p r o d u c t s . The m o l a r y i e l d was 82%. (12) The F o r m a t i o n of C a t e c h o l from C a t e c h i n i n t h e P r e s e n c e and Absence of 0 2 P y r e x r e a c t i o n t u b e s were made by f l a m e - s e a l i n g one end of f o u r p i e c e s of 15 cm l o n g , 7 mm O.D., 5 mm I.D: t u b i n g . A s o l u t i o n made from c a t e c h i n (25 mg), ( N H , ) 2 S 0 3 (150 mg) and 1 57 c o n c e n t r a t e d N H„OH (350 mg) was put i n e a c h t u b e . A d i s p o s a b l e p i p e t t e drawn t o a f i n e d i a m e t e r t i p was t h e n u s e d t o b u b b l e e i t h e r 0 2 , N 2 or a i r i n t o t h e s o l u t i o n i n one of t h e t u b e s . The u n t r e a t e d s o l u t i o n and t h e one b u b b l e d w i t h a i r were t h e c o n t r o l s a m p l e s . A f t e r b u b b l i n g t h e gas t h r o u g h t h e s o l u t i o n f o r 1 m i n u t e , t h e open end o f t h e r e a c t i o n t u b e was c l o s e d w i t h a p i p e t t e b u l b . Then the r e a c t i o n t u b e was s e a l e d by c r i m p i n g t h e f l a m e - h e a t e d t u b i n g 2 cm from t h e r u b b e r b u l b . A f t e r h e a t i n g i n an oven a t 150° C f o r 3 h o u r s , t h e r e a c t i o n s o l u t i o n s were a s s a y e d f o r c a t e c h o l c o n t e n t f o l l o w i n g t h e p r o c e d u r e o u t l i n e d i n s e c t i o n VI-B. C h a p t e r 1 1 ( 2 ) . No s i g n i f i c a n t d i f f e r e n c e s i n t h e y i e l d s of c a t e c h o l from t h e d i f f e r e n t r e a c t i o n c o n d i t i o n s c o u l d be d e t e r m i n e d . (13) I d e n t i f i c a t i o n o f P r o d u c t s from t h e R e a c t i o n of W e s t e r n Hemlock Bark P o l y p h e n o l s w i t h ( N H „ ) 2 S 0 3 / N H 3 F r e s h l y c o l l e c t e d , , c o a r s e l y g r o u n d bark (1466 g, MC=46.8%, Dry weight=779.9 g) was e x t r a c t e d w i t h e t h a n o l ( 4 - l i t e r s ) i n a S o x h l e t f o r 24 h r s . E v a p o r a t i o n o f t h e e t h a n o l s o l u t i o n gave 206.9 g of s o l i d (26.5% y i e l d ) . F i v e grams of e t h a n o l e x t r a c t p r e p a r e d above was h e a t e d t o 175° C f o r 2 h r s . w i t h ( N H „ ) 2 S 0 3 (5 g) and c o n c e n t r a t e d NH»OH (45 g) i n a s e a l e d s t a i n l e s s s t e e l r e a c t i o n v e s s e l . A f t e r c o o l i n g and b u b b l i n g w i t h N 2 t o remove most of t h e NH 3, the s o l u t i o n was e x t r a c t e d w i t h f o u r p o r t i o n s of d i e t h y l e t h e r (50 1 58 ml e a c h ) . The o r g a n i c l a y e r s were combined, d r i e d w i t h MgS0 4 and e v a p o r a t e d . The s o l i d s were, a n a l y s e d by GC-MS. B e s i d e s t h e a r o m a t i c compounds l i s t e d below, some f a t t y a c i d s and h y d r o c a r b o n s were i d e n t i f i e d . C a t e c h o l (major component) - MS - 110(100), 9 2 ( 1 1 ) , 8 2 ( 4 ) , 81 ( 1 0 ) , 6 4 ( 1 6 ) , 6 3 ( 1 4 ) . P h e n o l (major) - MS - 9 5 ( 7 ) , 9 4 ( 1 0 0 ) , 6 6 ( 2 1 ) , 6 5 ( 2 1 ) , 5 5 ( 9 ) , 5 0 ( 5 ) . M e t h y l p h e n o l ( m i n o r , p o s i t i o n of m e t h y l g r o u p u n c e r t a i n ) MS - 109 108(100), 1 0 7 ( 8 6 ) , 9 1 ( 8 ) , 9 0 ( 2 3 ) , 8 9 ( 1 4 ) , 7 9 ( 3 1 ) , 7 7 ( 3 5 ) , 5 3 ( 1 5 ) , 5 1 ( 1 7 ) . M e t h o x y p h e n o l (minor component, p o s i t i o n of t h e methoxy g r o u p u n c l e a r ) - MS - 1 2 5 ( 5 ) , 1 2 4 ( 7 5 ) , 1 0 9 ( 1 0 0 ) , 8 1 ( 6 1 ) , 6 5 ( 7 ) , 63(8) , 53(24) . D i m e t h o x y p h e n o l (minor component, p o s i t i o n o f methoxy g r o u p s u n c e r t a i n ) - MS - 1 5 5 ( 8 ) , 154(100), 1 3 9 ( 4 7 ) , 1 1 1 ( 2 7 ) , 9 6 ( 3 4 ) , 9 3 ( 2 3 ) , 7 9 ( 1 4 ) , 6 8 ( 1 4 ) , 6 5 ( 2 4 ) . VI-D. C h a p t e r IV (1) I s o l a t i o n of t h e O r g a n i c P r o d u c t s from t h e R e a c t i o n of W e s t ern Hemlock Bark w i t h ( N H „ ) 2 S 0 3 / N H 3 f o r A d h e s i v e F o r m u l a t i o n G r ound w e s t e r n hemlock bark (330 g, 17.5% MC, 247.5 g d r y w e i g h t ) , 100 g of ( N H 4 ) 2 S 0 3 and 1.2 l i t e r s of c o n c e n t r a t e d ammonia were p l a c e d i n a 2 l i t e r P a r r h y d r o g e n a t i o n a p p a r a t u s 1 59 e q u i p p e d w i t h a g l a s s l i n e r and a m e c h a n i c a l s t i r r e r . The m i x t u r e was s t i r r e d w i t h an aluminum r o d t o o b t a i n a s l u r r y of even c o n s i s t e n c y . A f t e r s e a l i n g t h e r e a c t i o n v e s s e l , i t was h e a t e d t o 175° C u s i n g an e x t e r n a l h e a t i n g j a c k e t and kept a t t h a t t e m p e r a t u r e , w i t h s t i r r i n g , f o r 2 h o u r s . A p r e s s u r e of a b o u t 400 p s i was g e n e r a t e d i n t h e r e a c t i o n v e s s e l . A f t e r c o o l i n g i n a l a r g e c o l d water b a t h , t h e a p p a r a t u s was opened and t h e . r e a c t i o n m i x t u r e f i l t e r e d t h r o u g h a l a r g e Buchner f u n n e l . Most of t h e l i q u i d was p r e s s e d out o f t h e bark r e s i d u e by u s i n g a r u b b e r s h e e t s e a l e d a c r o s s t h e t o p of t h e f u n n e l . The s o l i d was washed w i t h two 200 ml p o r t i o n s of c o n c e n t r a t e d ammonia s o l u t i o n and t h e n 500 ml of d i s t i l l e d w a t e r . The bark r e s i d u e was d r i e d i n an oven t o a c o n s t a n t w e i g h t of 157 g. A s s u m i n g t h a t no s u l p h i t e was " r e m a i n i n g i n t h e s o l i d , ' t h e e x t r a c t i o n / r e a c t i o n y i e l d was 36.5%. The i n i t i a l f i l t r a t e and w a s h i n g s from above were combined and e v a p o r a t e d t o a s o l i d . T h i s amorphous, dark-brown m a t e r i a l was s u s p e n d e d i n 200 ml o f d i s t i l l e d water (pH of t h e s o l u t i o n was 7.5) and vacuum f i l t e r e d . The s o l i d was washed s e v e r a l t i m e s w i t h water and r e f i l t e r e d t o g i v e 88.6 g of p r o d u c t (45% MC, 44 g d r y w e i g h t ) . E x c e s s (NH,,) 2S03 was removed from t h e c ombined f i l t r a t e and w a s h i n g s by one of two methods: (1) A f t e r e v a p o r a t i o n t o a b o u t 25 ml, 200 ml of e t h a n o l was added t o t h e s o l u t i o n w i t h s t i r r i n g . The p r e c i p i t a t e d s a l t s were f i l t e r e d out and t h e s o l u t i o n e v a p o r a t e d t o 15 m l . The e t h a n o l a d d i t i o n , f i l t r a t i o n and e v a p o r a t i o n was r e p e a t e d t o g i v e 15 g of a v i s c o u s , y e l l o w - b r o w n s o l u t i o n 160 ( 4 5 % s o l i d s , 7 g d r y w e i g h t ) . (2) A f t e r e v a p o r a t i o n t o about 100 ml, t h e s o l u t i o n was h e a t e d t o 50° C on a hot p l a t e w i t h m a g n e t i c s t i r r i n g . A c e r t a i n amount o f B a ( O H ) 2 (20 g t o 60 g) d i s s o l v e d i n ' 100 ml of b o i l i n g water was t h e n s l o w l y added, and t h e r e s u l t i n g s o l u t i o n was a l l o w e d t o c o o l t o room t e m p e r a t u r e . The p r e c i p i t a t e d B a S 0 3 was t h e n _ f i l t e r e d out and t h e f i l t r a t e was e v a p o r a t e d t o a s m a l l volume. (2) G e n e r a l Method of A d h e s i v e F o r m u l a t i o n U s u a l l y , two f r a c t i o n s r e s u l t e d from t h e i s o l a t i o n of o r g a n i c m a t e r i a l from t h e c l e a v a g e r e a c t i o n on hemlock b a r k o r g a n i c s s o l u b l e and i n s o l u b l e i n water a t pH 7.5. The r a t i o of the f r a c t i o n s i n t h e g l u e mix was t h e same as t h e r a t i o i n wh i c h t h e y were p r o d u c e d . The s o l u b l e f r a c t i o n (2 g, 45% s o l i d s ) was n o r m a l l y p r e - m e t h y l o l a t e d by r e a c t i n g w i t h p a r a f o r m a l d e h y d e , (0.13 g) and 0.4 g of 50% NaOH s o l u t i o n a t 100° C f o r 0.5 h r s . The pH of t h e s o l u t i o n was 10.5. A f t e r c o o l i n g , t h e s o l u t i o n was combined w i t h 10 g of t h e n e u t r a l - i n s o l u b l e m a t e r i a l (55% s o l i d s ) , more 50% NaOH s o l u t i o n (1.6 g ) , hexamine (1.0 g) or p a r a f o r m a l d e h y d e (0.8 g ) , CoCob f i l l e r (2 g ) , wheat f l o u r (0.4 g) and water (2 g ) . T h i s m i x t u r e was m a n u a l l y s t i r r e d u n t i l smooth. I f n e c e s s a r y , more water was added t o r e d u c e t h e v i s c o s i t y t o an e a s i l y s p r e a d a b l e l e v e l . The s o l i d s c o n t e n t of th e f i n a l g l u e mix was 45 t o 50%. 161 (3) Q u a l i t a t i v e T e c h n i q u e f o r A d h e s i v e Bond E v a l u a t i o n The a d h e s i v e m i x t u r e t o be t e s t e d was a p p l i e d w i t h a s p a t u l a t o a 10 cm by 10 cm a r e a on t h e t i g h t f a c e o f a p i e c e of v e n e e r (0.1 i n c h e s t h i c k ) w i t h d i m e n s i o n s o f 10 cm X 30 cm. The l o a d i n g was a p p r o x i m a t e l y 3 g/100 cm 2. A f t e r a m e a s u r e d open a s s e m b l y t i m e ( t y p i c a l l y 20 m i n . ) , a n o t h e r s i m i l a r p i e c e of v e n e e r was p l a c e d a t r i g h t a n g l e s o v e r t h e a d h e s i v e - s p r e a d a r e a . The s e c o n d p i e c e o f v e n e e r had i t s l o o s e s u r f a c e ( l a t h e - c h e c k e d ) f a c i n g downward and c o n t a c t i n g t h e a d h e s i v e i n t h e g l u e l i n e . T h i s a s s e m b l y was t h e n p r e s s e d u n d e r t h e f o l l o w i n g c o n d i t i o n s : ..Press T e m p e r a t u r e - 175 d e g r e e s C P r e s s Time ,- 2 m i n . P r e s s u r e - 200 p s i A f t e r l e t t i n g c o o l f o r a b o u t 30 m i n . , t h e q u a l i t y o f t h e g l u e l i n e was e v a l u a t e d by m a n u a l l y t w i s t i n g t h e p i e c e s o f v e n e e r a p a r t a t t h e g l u e l i n e . The q u a l i t a t i v e wet s t r e n g t h o f a bond was d e t e r m i n e d by s u b m e r g i n g t h e 10 cm X 10 cm sample u n d e r w a t e r i n a s m a l l d e s i c c a t o r . The a i r s p a c e was e v a c u a t e d u s i n g an a s p i r a t o r , and l e f t a t l e a s t 12 h o u r s u n d e r s u c t i o n . Bond q u a l i t y was e v a l u a t e d by manual b r e a k a g e . 1 62 (4) Q u a n t i t a t i v e E v a l u a t i o n of Bond S t r e n g t h T h r e e - p l y 8 X 1 2 i n c h p l y w o o d p a n e l s were made u s i n g t h e a d h e s i v e m i x t u r e t o be t e s t e d w i t h t h e l o n g i t u d i n a l d i r e c t i o n o f t h e f a c e and back v e n e e r s o r i e n t e d p a r a l l e l t o t h e s h o r t a x i s o f t h e p a n e l . T y p i c a l a s s e m b l y and p r e s s p a r a m e t e r s were a s f o l l o w s : A s s e m b l y Time - 20 - 25 min. A d h e s i v e L o a d i n g - 2.33 g/100 cm 2 ( s i n g l e g l u e l i n e ) P r e s s Time - 4 m i n . P r e s s T e m p e r a t u r e - 175° C P r e s s u r e - 200 p s i The 8 X 12 i n c h s i z e a l l o w e d t w e n t y 1 X 3 i n c h s h e a r s a m p l e s t o be c u t f r o m e a c h p a n e l . G r o o v i n g was done s u c h t h a t h a l f o f t h e s a m p l e s f r o m a g i v e n p a n e l were t e s t e d w i t h t h e l a t h e c h e c k s b e i n g p u l l e d open a n d t h e o t h e r h a l f w i t h t h e l a t h e c h e c k s , p u l l e d c l o s e d ( F i g u r e V I - 1 ) . Ten s a m p l e s ( f i v e o f e a c h l a t h e c h e c k o r i e n t a t i o n ) were t e s t e d d r y and t h e r e s u l t i n g s h e a r s t r e n g t h s and wood f a i l u r e d e t e r m i n e d . The o t h e r t e n s a m p l e s were s u b m e r g e d i n w a t e r i n a f i l t r a t i o n f l a s k w i t h s u c t i o n f r o m an a s p i r a t o r f o r 12 h o u r s . T h e s e wet s a m p l e s were a l s o t e s t e d f o r s h e a r s t r e n g t h . Some t e s t i n g was a l s o done w i t h 4 i n c h X 5 i n c h t e s t p a n e l s . In t h i s c a s e o n l y 4 s h e a r s a m p l e s c o u l d be c u t f r o m e a c h b o a r d . T h e i r t e s t i n g a n d a n a l y s i s were a s d e s c r i b e d above f o r s a m p l e s f r o m t h e l a r g e r p a n e l s . 1 6 3 l — 1 in Lathe Checks Lathe Checks Pulled Closed Pulled Open F i g u r e V I - 1 . S h e a r T e s t Samples 1 64 BIBLIOGRAPHY (1) P a n s h i n , A . J . and C. de Zeeuw. 1980. T e x t b o o k o f Wood T e c h n o l o g y . M c G r a w - H i l l , T o r o n t o , p. 49. (2) Chang, Y.-P. 1954. Anatomy o f Common N o r t h A m e r i c a n P u lpwood B a r k s . T a p p i Monograph S e r i e s - No. 14, New Y o r k . (3) S m i t h , J.H.G. and A. K o z a k . 1971. T h i c k n e s s , M o i s t u r e C o n t e n t a n d S p e c i f i c G r a v i t y o f I n n e r and O u t e r Bark o f Some P a c i f i c N o r t h w e s t T r e e s . F o r e s t P r o d . J . 2 1 ( 2 ) : 3 8 . (4) Chang, T.-P. 1954. B a r k S t r u c t u r e o f N o r t h A m e r i c a n C o n i f e r s . T e c h n i c a l B u l l e t i n 1095, USDA:45. (5) Meyer, R.W., R.M. K e l l o g g a n d W.G. W a r r e n . 1981. R e l a t i v e D e n s i t y , E q u i l i b r i u m M o i s t u r e C o n t e n t a n d D i m e n s i o n a l S t a b i l i t y o f W e s t e r n Hemlock B a r k . Wood and F i b e r 13(2):86. (6) B r a m h a l l , A.E., R.M. K e l l o g g , R.W. Meyer a n d W.G. W a r r e n . 1977. B a r k - T i s s u e T h i c k n e s s o f C o a s t a l W e s t e r n Hemlock i n B r i t i s h C o l u m b i a . Wood a n d F i b e r 9 ( 3 ) : 1 8 4 . (7) H a l l , J.A. 1971. U t i l i z a t i o n o f D o u g l a s F i r B a r k . P a c i f i c N o r t h w e s t F o r e s t a n d Range E x p e r i m e n t S t a t i o n , F o r e s t S e r v i c e , USDA, P o r t l a n d , O r e g o n . (8) H e r r i c k , F.W. and H.L. H e r g e r t . 1977. U t i l i z a t i o n o f C h e m i c a l s f r o m Wood: R e t r o s p e c t a n d P r o s p e c t . I n "R e c e n t A d v a n c e s i n P h y t o c h e m i s t r y " . F.A. Loewus a n d V.C. R u n e c k l e s e d s . Plenum P r e s s . New Y o r k . p. 445. (9) H e r g e r t , H.L., L . E . Van B l a r i c o m , J . C . S t e i n b e r g and K.R. G r a y . 1965. I s o l a t i o n a n d P r o p e r t i e s o f D i s p e r s a n t s f r o m W e s t e r n Hemlock B a r k . F o r e s t P r o d . J . 1 5 ( 1 1 ) : 4 8 5 . (10) S a r k a n e n , K.V. a n d H.L. H e r g e r t . 1971. C l a s s i f i c a t i o n a n d D i s t r i b u t i o n . I n " L i g n i n s ; O c c u r r e n c e , F o r m a t i o n , S t r u c t u r e and R e a c t i o n s " , K.V. S a r k a n e n and C.H. L u d w i g 1 65 e d s . , J . W i l e y and Sons, New Y o r k , Ch.3. (11) Swan, E.P. 1966. A S t u d y o f W e s t e r n Red C e d a r L i g n i n . P u l p Pap. Mag. Can. 67:456. (12) G a r d n e r , P.E. 1957. A S t u d y o f t h e C o m p l e t e l y E x t r a c t e d F i b r o u s P o r t i o n o f W h i t e S p r u c e B a r k . Ph. D. T h e s i s , M c G i l l U n i v e r s i t y , M o n t r e a l . (13) B i n n o t t o , A.P., W.K. Murphy and B.E. C u t t e r . 1971. X-Ray D i f f r a c t i o n S t u d i e s o f C e l l u l o s e From B a r k and Wood. Wood and F i b e r 3 ( 2 ) : 1 7 9 . (14) K i e f e r , H . J. and E . F . K u r t h . 1953. The C h e m i c a l C o m p o s i t i o n o f t h e B a s t F i b e r o f D o u g l a s - F i r B a r k . T a p p i 36:14. (15) Sogo, M., T. I s h i h a r o and K. H a t a . 1966. C h e m i c a l S t u d i e s on t h e B a r k . X I I I On t h e H y d r o g e n o l y s i s o f t h e O u t e r Bark L i g n i n o f P i n u s d e n s i f l o r a . J . J p n . Wood R e s . S o c . 12:96. (16) Sogo, M. and K. H a t a . 1968. C h e m i c a l S t u d i e s on t h e B a r k . XVI On t h e A r o m a t i c N u c l e i o f U n d i s s o l v a b l e B a r k L i g n i n . J . J p n . Wood Res.. S o c . 14:334. (17) H e r g e r t , H.L. 1971. The C h e m i s t r y and U t i l i z a t i o n o f Non-L i g n i n P h e n o l i c P o l y m e r s f r o m C o n i f e r s . P a p e r P r e s e n t e d t o t h e 1 61st N a t i o n a l ACS M e e t i n g , W a s h i n g t o n , D . C . (18) Roux, D.G. 1952. Improved D e g r a d a t i o n Methods f o r E x a m i n a t i o n o f B l a c k W a t t l e and A l l i e d T a n n i n s . J . S o c . L e a t h e r T r a d e s C h e m i s t s 36:393. (19) H e r g e r t , H.L. 1960. C h e m i c a l C o m p o s i t i o n o f T a n n i n s a n d P o l y p h e n o l s f r o m C o n i f e r Wood a n d B a r k . F o r e s t P r o d . J . 10:610. (20) Hemingway, R.W. 1981. B a r k : I t s C h e m i s t r y and P r o s p e c t s f o r C h e m i c a l U t i l i z a t i o n . I n " O r g a n i c C h e m i c a l s f r o m B i o m a s s " , I . S . G o l d s t e i n e d . , CRC P r e s s I n c . , Boca R a t o n , F l a . Ch. 10:189. 1 66 (21) S e a r s , K.D. and R.L. C a s e b i e r . 1970. The R e a c t i o n of T h i o g l y c o l i c A c i d w i t h P o l y f l a v a n o i d B a r k F r a c t i o n s o f T s u q a h e t e r o p h y 1 1 a . P h y t o c h e m i s t r y 9:1589. (22) F l e t c h e r , A.C., L . J . P o r t e r , E. H a s l a m and R.K. G u p t a . 1977. P l a n t P r o a n t h o c y a n i d i n s . P a r t 3 C o n f o r m a t i o n a l and C o n f i g u r a t i o n a l S t u d i e s o f N a t u r a l P r o c y a n i d i n s . J . C . S . P e r k i n T r a n s . 1 :1628 . (23) G u p t a , R.K. a n d E. H a s l a m . 1978. P l a n t P r o a n t h o c y a n i d i n s . P a r t 5 Sorghum P o l y p h e n o l s . J . C . S . P e r k i n T r a n s . 1:892. (24) H a s l a m , E . 1977. Symmetry and P r o m i s c u i t y i n P r o c y a n i d i n B i o c h e m i s t r y . P h y t o c h e m i s t r y 16:1625. (25) Hemingway, R.W., G.W. McGraw, J . J . K a r c h e s y , L.Y. Foo and L . J . P o r t e r . 1983. R e c e n t A v a n c e s i n t h e C h e m i s t r y o f C o n d e n s e d T a n n i n s . J . A p p l . S c i . Symp. 37:967. (26) Hemingway, R.W., L.Y. Foo a n d L . J . P o r t e r . 1982. L i n k a g e " i s o m e r i s m i n T r i m e r i c and P o l y m e r i c 2 , 3 - c i s -P r o c y a n i d i n s . J . Chem. S o c . P e r k i n T r a n s . 1:1209. (27) Hemingway, R.W., J . J . K a r c h e s y , G.W. McGraw and R.A. W i e l e s e k . 1983. H e t e r o g e n e i t y o f I n t e r f l a v a n o i d Bond L o c a t i o n i n L o b l o l l y P i n e B a r k P r o c y a n i d i n s . P h y t o c h e m . 2 2 ( 1 ) : 2 7 5 . (28) Hemingway, R.W., L.Y. Foo a n d L . J . P o r t e r . 1981. P o l y m e r i c P r o a n t h o c y a n i d i n s : I n t e r f l a v a n o i d L i n k a g e I s o m e r i s m i n ( E p i c a t e c h i n - 4 ) - • ( E p i c a t e c h i n - 4 ) - C a t e c h i n P r o c y a n i d i n s . J . Chem. S o c . Chem. Commun., 320. (29) H e r g e r t , H.L. 1962. E c o n o m i c I m p o r t a n c e o f F l a v a n o i d Compounds :Wood and B a r k . In "The C h e m i s t r y o f F l a v a n o i d Compounds". T.A. G e i s s m a n n E d . , M a c M i l l a n , New Y o r k , Ch. 17. (30) H e r r i c k , F.W. and H.L. H e r g e r t . 1977. U t i l i z a t i o n o f C h e m i c a l s f r o m Wood: R e t r o s p e c t and P r o s p e c t . I n " R e c e n t A d v a n c e s i n P h y t o c h e m i s t r y " . F.A. Loewus an d V.C. R u n e c k l e s e d s . Plenum P r e s s . New Y o r k . p. 465. 167 (31) H e r g e r t , H.L. 1958. Chemical Composition of Cork from White F i r bark. F o r e s t Prod. J . 8:335. (32) F r a s e r , H.S. and E.P. Swan. 1979. P h e n o l i c C h a r a c t e r of S e q u e n t i a l S o l v e n t E x t r a c t s from Western Hemlock and White Spruce B a r k s . Can. J . For.Res. 9(4):495. (33) Sears, K.D., R.L. C a s e b i e r , H.L. H e r g e r t , G.H. Stout and L.E. M c C a n d l i s h . 1974. The S t r u c t u r e of C a t e c h i n i c A c i d . A Base Rearrangement Product of C a t e c h i n . J . Org. Chem. 39(22):3244. (34) White, J.T. 1980. S t a t u s and F o r e c a s t f o r Supply, Demand and Cost of Wood Adhesive and B i n d e r s . In P r o c . of 1980 Symp., "Wood A d h e s i v e s - Research, A p p l i c a t i o n and Needs." USDA F o r e s t S e r v i c e , F o r e s t Products Lab, Madison, Wis., p. 9. (35) P i z z i , A., R.M. Horak, D. F e r r e i r a and D.G. Roux. 1979. Condensates of Phenol, R e s o r c i n o l , and P y r o g a l l o l as Model Compounds of F l a v a n o i d A- and B-Rings w i t h Formaldehyde. C e l l u l o s e Chem. T e c h n o l . 13:753. (36) Walker, J . F . 1964. Formaldehyde. ACS Monograph No. 159, 3rd Ed., R e i n h o l d , New York. (37) S t e i n e r , P.R. P e r s o n a l Communication (38) Kopf, P.W. and E.R. Wagner. 1973. Formation and Cure of Novolaks. NMR Study of T r a n s i e n t M o l e c u l e s . Polym. S c i . Polym. Chem. E d . I I , p. 939. (39) MacLean, H. and J.A.F. Gardner. 1952. Bark E x t r a c t i o n i n A d h e s i v e s . P u l p Pap. Mag. Can., Aug., p. 111. (40) H e r r i c k , F.W. and L.H. Bock. 1958. T h e r m o s e t t i n g , E x t e r i o r - P l y w o o d Type. Ad h e s i v e s from Bark E x t r a c t s . F o r e s t Prod. J . 8(10):269. (41) Brode, G.L. 1982. P h e n o l i c R e s i n s . In " E n c y c l o p e d i a of Chemical Technology", 3rd Ed., J . W i l e y and Sons, New York, V o l . 17, p. 384. 1 68 (42) Megson, N . J . L . 1958. P h e n o l i c R e s i n C h e m i s t r y , B u t t e r w o r t h s P u b l i c . , L o n d o n . (43) K n o p f , A. and W. S c h e i b . 1979. C h e m i s t r y and A p p l i c a t i o n o f P h e n o l i c R e s i n s , S p r i n g e r - V e r l a g P u b l i s h i n g Co., New Y o r k . (44) H e r r i c k , F.W. 1980. C h e m i s t r y and U t i l i z a t i o n o f W e s t e r n Hemlock Bark E x t r a c t i v e s . J . A g r i c . F o o d Chem. 2 8 ( 2 ) : 2 2 8 . (45) M c N u t t , L . L . 1976. O u t l o o k t o 1980 F o r P l y w o o d A d h e s i v e s . In "Modern P l y w o o d T e c h n i q u e s " . H.G. L a m b e r t E d . , M i l l e r Freeman 4:30. (46) H e r r i c k , F.W. and R . J . C o n c a . 1960. The Use o f B a r k E x t r a c t s i n C o l d s e t t i n g W a t e r p r o o f A d h e s i v e s . F o r e s t P r o d . J . 10(7) :361 . (47) A n d e r s o n , A.B., A. Wong and K.T. Wu. 1975. D o u g l a s F i r and W e s t e r n Hemlock Bark E x t r a c t s a s B o n d i n g A g e n t s f o r P a r t i c l e b o a r d . F o r e s t P r o d . J . 2 5 ( 3 ) : 4 5 . (48) S t e i n e r , P.R. a n d S. Chow. 1975. Some F a c t o r s I n f l u e n c i n g t h e Use o f W e s t e r n Hemlock Bark E x t r a c t s a s A d h e s i v e s . P r o c . IUFRO C o n f . Wood G l u i n g , M a d i s o n , W i s . , 6 1 . (49) Anonymous. 1950. B a r k Wax. Chemurg. D i g . 9 ( 7 ) : 9 . (50) H e r r i c k , F.W. 1971. U s e f u l P r o d u c t s D e r i v e d f o r m C o n i f e r T r e e B a r k by C h e m i c a l E x t r a c t i o n . I n " P r o c e e d i n g s o f C o n f e r e n c e : C o n v e r t i n g B a r k i n t o O p p o r t u n i t i e s " , OSU S c h o o l o f F o r e s t r y , C o r v a l l i s , O r e g o n , p. 101. (51) A a r o n , J.R. 1982. C o n i f e r B a r k : I t s P r o p e r t i e s and U s e s . F o r e s t r y C o m m i s s i o n F o r e s t R e c o r d 110, Her M a j e s t y ' s S t a t i o n a i r y O f f i c e , G r e a t B r i t a i n . (52) S e a r s , K.D. 1972. S u l p h o n a t i o n o f C a t e c h i n . J . O r g . Chem. 3 7 ( 2 2 ) : 3 5 4 6 . (53) Van B l a r i c o m , L . E . a n d L . E . G r a y . 1960. U.S. P a t e n t 1 69 2,964,469 t o R a y o n i e r I n c . (54) D u r k e e , G.E. 1965. M i c r o n u t r i e n t F o l i a r S p r a y s . A g r i c h e m . West 1:17. (55) Manas, A.E. 1982. T a n n i n E x t r a c t i o n and U t i l i z a t i o n f r o m Bakauan B a r k s . NSTA T e c h n o l o g y J . J a n . - M a r . , 57. (56) B r a n d t , T.G. 1952. Mangrove T a n n i n - F o r m a l d e h y d e R e s i n s a s H o t - P r e s s s e d P l y w o o d A d h e s i v e s . T e c t o n a 42:137. (57) K i l p e l a i n e n , H. and H. S a i r a n e n . 1980. The Use o f B a r k E x t r a c t i n P l y w o o d A d h e s i v e s . IUFRO C o n f e r e n c e P r o c e e d i n g s . S5.04-07 Wood P r o c e s s i n g S u b j e c t G r o u p , A p r i l 8-16, O x f o r d , G r e a t B r i t a i n . (58) A y l a , C. and N. P a r a m e s w a r a n . 1980. M a c r o - and M i c r o -T e c h n o l o g i c a l S t u d i e s on Beechwood P a n e l s Bonded w i t h P i n u s  B r u t i a B a r k T a n n i n s . H o l z a l s Roh- und W e r k s t o f f 38:449. (59) K u b o t a , M., S. H i r a t a a n d H. T a k a h a s h i . 1980. The U t i l i z a t i o n o f L a r c h B a r k E x t r a c t s f o r Wood A d h e s i v e s . The P r o p e r t i e s o f t h e A c i d i f i c a t i o n P r e c i p i t a t e f r o m M e t h y l o l a t e d Hot Water E x t r a c t . J . H o k k a i d o F o r e s t P r o d . R e s . I n s t . 346:1. (60) H i l l i s , W.E. 1981. N a t u r a l P o l y p h e n o l s ( T a n n i n s ) a s a B a s i s f o r A d h e s i v e s . I n " W e y e r h a u s e r S c i e n c e Symposium, P h e n o l i c R e s i n s , C h e m i s t r y and A p p l i c a t i o n " . W e y e r h a u s e r Co, p. 171. (61) Roux, D.G. a n d M.C. B i l l . 1959. M e c h a n i s m o f F o r m a t i o n o f A n t h o c y a n i d i n s f r o m L e u c o a n t h o c y a n i d i n s . N a t u r e ( L o n d o n ) 183:42. (62) Drewes, S.E. and D.G. Roux. 1963. C o n d e n s e d T a n n i n s XV. I n t e r r e l a t i o n s o f F l a v a n o i d Components i n W a t t l e - B a r k E x t r a c t . B i o c h e m J . 87:167. (63) Hemingway, R.W. 1978. A d h e s i v e s from S o u t h e r n P i n e Bark -A R eview o f P a s t a n d C u r r e n t A p p r o a c h e s t o R e s i n F o r m u l a t i o n P r o b l e m s . P r o c . FPRS Symp. on C o m p l e t e T r e e U t i l i z a t i o n o f S o u t h e r n P i n e , New O r l e a n s , A p r i l 17-19, p. 163. 170 (64) Hemingway, R.W. and G.W. McGraw. 1976. P r o g r e s s i n t h e C h e m i s t r y o f S h o r t l e a f and L o b l o l l y P i n e B a r k F l a v a n o i d s . A p p l . P o l y m . Symp. 28:353. (65) P i z z i , A. 1982.. C o n d e n s e d T a n n i n s f o r A d h e s i v e s . I n d . Eng. Chem. P r o d . R e s . Dev. 21:359. (66) P o r t e r , L . J . 1974. E x t r a c t i v e s o f P i n u s R a d i a t a B a r k 2. P r o c y a n i d i n C o n s t i t u e n t s . N . Z . J . S c i . 17:213. (67) H i l l i s , W.E. and G. Ur b a c h . - 1959. R e a c t i o n s o f P o l y p h e n o l s w i t h F o r m a l d e h y d e . J . A p p l . Chem. 9:665. (68) Roux, D.G., D. F e r r e i r a , H.K.L. Hundt a n d E. M a l a n . 1975. S t r u c t u r e , S t e r e o c h e m i s t r y and R e a c t i v i t y o f N a t u r a l C o n d e n s e d T a n n i n s a s B a s i s f o r T h e i r E x t e n d e d I n d u s t r i a l A p p l i c a t i o n . A p p l . P o l y m . Symp. 28:335. (69) Hemingway, R.W. a n d G.W. McGraw. 1977. I n "1977 TAPPI F o r e s t B i o l . / W o o d Chem. C o n f . " , M a d i s o n , W i s . , p.261. (70) Y a z a k i , Y. and, W.E. H i l l i s . 1977. P o l y p h e n o l i c E x t r a c t i v e s o f P i n u s R a d i a t a B a r k . H o l z f o r s c h u n g 31:20. (71) Y a z a k i , Y. and W.E. H i l l i s . 1980. M o l e c u l a r S i z e D i s t r i b u t i o n of R a d i a t a P i n e B a r k E x t r a c t s a n d i t s E f f e c t on P r o p e r t i e s . H o l z f o r s c h u n g 34:125. (72) Saayman, H.M. and J.A. O a t l e y . 1976. Wood A d h e s i v e s f r o m W a t t l e B a r k E x t r a c t . F o r e s t P r o d . J . 2 6 ( 1 2 ) : 2 7 . (73) P i z z i , A. 1978. W a t t l e - B a s e A d h e s i v e s f o r E x t e r i o r G r a d e P a r t i c l e b o a r d s . F o r e s t P r o d . J . 2 8 ( 1 2 ) : 4 2 . (74) P i z z i , A. a n d M. M e r l i n . 1981. A New C l a s s o f T a n n i n A d h e s i v e s f o r E x t e r i o r P a r t i c l e b o a r d . I n t . J . A d h e s . A d h e s . 1:261. (75) P i z z i , A. a n d H . J . S c h a r f e t t e r . 1978. The C h e m i s t r y a n d D e v e l o p m e n t o f T a n n i n - B a s e d A d h e s i v e s f o r E x t e r i o r P l y w o o d . J . A p p l . P olym. S c i . 22:1745. 171 (76) P i z z i , A. 1980. T a n n i n - B a s e d A d h e s i v e s . J . Macromol S c i . , Rev. M a c r o m o l . Chem. C 1 8 ( 2 ) : 2 4 7 . (77) P i z z i , A. 1977. H o t - S e t t i n g T a n n i n - U r e a - F o r m a l d e h y d e E x t e r i o r Wood A d h e s i v e s . A d h e s i v e s Age 2 0 ( 1 2 ) : 2 7 . (78) C o p p e n s , H.A., M.A.E. S a n t a n a and F . J . P a s t o r e . 1980. ~' T a n n i n F o r m a l d e h y d e A d h e s i v e f o r E x t e r i o r - G r a d e P l y w o o d and P a r t i c l e b o a r d M a n u f a c t u r e . F o r e s t P r o d . J . 3 0 ( 4 ) : 3 8 . (79) P i z z i , A. 1979. P h e n o l i c and T a n n i n - B a s e d A d h e s i v e R e s i n s b y ^ R e a c t i o n s of C o o r d i n a t e d M e t a l L i g a n d s . I I T a n n i n A d h e s i v e P r e p a r a t i o n , C h a r a c t e r i s t i c s and A p p l i c a t i o n . J . A p p l . P olym. S c i . 24:1257. (80) P i z z i , A. and G.M.E. D a l i n g . 1980. L a m i n a t i n g Wood A d h e s i v e s by G e n e r a t i o n o f R e s o r c i n o l f r o m T a n n i n E x t r a c t s . J . Polym. S c i . 25:1039. (81) K r i e b i c h , R.E. 1974. H i g h Speed A d h e s i v e s f o r t h e Wood-G l u i n g I n d u s t r y . A d h e s i v e Age 17:26. (82) Van Der W e s t h u i z e n , P.K., A. P i z z i a nd H.S. S c h a r f e t t e r . 1977. A F a s t S e t t i n g W a t t l e A d h e s i v e f o r F i n g e r j o i n t i n g . I n t e r n a t i o n a l U n i o n o f F o r e s t R e s e a r c h O r g a n i z a t i o n C o n f . P a p e r , M e r i d a , V e n e z u a l a . (83) Cameron, F.A. and A. P i z z i . 1981. CSIR S p e c i a l R e p o r t . HOUT 207, P r e t o r i a , S o u t h A f r i c a . a s q u o t e d i n R e f . 65. (84) P i z z i , A., D. Rossouw, W. K n u f f e l and M. S i n g m i n . 1980. "Honeymoon" P h e n o l i c and T a n n i n - B a s e d F a s t - S e t t i n g A d h e s i v e S y s t e m s f o r E x t e r i o r G r a d e F i n g e r - J o i n t s . H o l z f o r s c h . H o l z v e r w e r t . 3 2 ( 6 ) : 1 4 0 . (85) C u s t o r s , P.A.J.L., R. R u s h b r o o k , A. P i z z i a n d C . J . K n a u f f . 1979. I n d u s t r i a l A p p l i c a t i o n o f W a t t l e T a n n i n / U r e a F o r m a l d e h y d e . F o r t i f i e d S t a r c h A d h e s i v e s f o r Damp-Proof C o r r u g a t e d C a r d b o a r d . H o l z f o r s c h . H o l z v e r w e r t . 3 1 ( 6 ) : 1 3 1 . (86) P i z z i , A. 1979. T a n n i n - B a s e d N e u t r a l a n d A l k a l i n e P h e n o l i c - T y p e Foams. J . A p p l . P o l y m . S c i . 23:1901. 1 72 (87) P i z z i , A. 1979. T a n n i n / P o l y u r e t h a n e A d h e s i v e s f o r B o n d i n g Aluminum. J . A p p l . P olym. S c i . 24:1579. (88) Chen, C M . 1982. C o p o l y m e r R e s i n s o f Bark and A g r i c u l t u r a l R e s i d u e E x t r a c t s w i t h P h e n o l and F o r m a l d e h y d e : 20 P e r c e n t W e i g h t o f P h e n o l R e p l a c e m e n t . F o r e s t P r o d . J . 3 2 ( 2 ) : 3 5 . (89) Chen, C M . 1982. C o p o l y m e r R e s i n s o f Bark and A g r i c u l t u r a l R e s i d u e E x t r a c t s w i t h P h e n o l and F o r m a l d e h y d e : 40 P e r c e n t W e i g h t o f P h e n o l R e p l a c e m e n t . F o r e s t P r o d . J . 3 2 ( 1 1 / 1 2 ) : 1 4 . (90) Hemingway, R.W. and G.W. McGraw. 1984. K i n e t i c s o f A c i d - C a t a l y s e d C l e a v a g e o f P r o c y a n i d i n s . Wood Chem. a n d T e c h n . , i n p r e s s . (91) C z o c h a n s k a , Z., L.Y. Foo, R.H. Newman and L . J . P o r t e r . 1980. P o l y m e r i c P r o a n t h o c y a n i d i n s . S t e r e o c h e m i s t r y , S t r u c t u r a l U n i t s and M o l e c u l a r W e i g h t . J . Chem. S o c . P e r k i n 1:2278. (92) Hemingway, R.W. and R.E. K r i e b i c h . 1983. C o n d e n s e d T a n n i n - R e s o r c i n o l A d d u c t s and T h e i r Use i n W o o d - L a m i n a t i n g A d h e s i v e s . IUFRO C o n f e r e n c e p r o c e e d i n g s , D i v . 5, J u n e , M a d i s o n , W i s e . . (93) Hemingway, R.W. a n d R . C Lloyd.. 1982. E c o n o m i c P r o s p e c t s f o r C o n i f e r B a r k E x t r a c t s . P a p e r p r e s e n t e d t o FPRS A n n u a l M e e t i n g , New O r l e a n s , L o u i s i a n a . (94) D a l t o n , L.K. 1952. R e s i n s f r o m S u l p h i t e d T a n n i n s a s A d h e s i v e s f o r Wood. A u s t r . J . o f A p p l . S c i . 4:136. (95) H a l l , R.B., .J.H. L e o n a r d a n d G.A. N i c h o l l s . 1960. B o n d i n g P a r t i c l e b o a r d s w i t h B a r k E x t r a c t s . F o r e s t P r o d . J . 1 0 ( 5 ) : 2 6 3 . (96) Y a z a k i , Y., W.E. H i l l i s a n d P . J . C o l l i n s . 1979. P u r i f i c a t i o n o f B a r k and Wood E x t r a c t s f o r Wood A d h e s i v e s . P a t e n t P r o v i s i o n a l S p e c i f i c a t i o n , A u s t r a l i a , May 1. (97) P i z z i , A. 1982. P i n e T a n n i n A d h e s i v e s f o r P a r t i c l e b o a r d . H o l z a l s Roh- und W e r k s t o f f 40:293. 1 73 (98) Woo, J.K. 1982. B a r k A d h e s i v e s f o r P a r t i c l e b o a r d and P l y w o o d . P a p e r p r e s e n t e d a t t h e I n t e r n a t i o n a l Symposium on A d h e s i o n a n d A d h e s i v e s f o r S t r u c t u r a l M a t e r i a l s . New Z e a l a n d . (99) H i l l i s , W.E. 1983. P e r s o n a l C o m m u n i c a t i o n . (100) S n e l l , F.D. 1961. C o l o r i m e t r i c M e t h o d s of A n a l y s i s . V o l I I I , D. Van N o s t r a n d Co., New J e r s e y , p.106. (101) Abe, I . 1979. U n p u b l i s h e d R e s u l t s . (102) Anon. 1982. C h r o m a t o g r a p h i c S p e c i a l t i e s R e s e a r c h S c i e n t i s t . P e r s o n a l C o m m u n i c a t i o n . (103) P a s t o , D . J . and C R . J o h n s o n . 1969. O r g a n i c S t r u c t u r e D e t e r m i n a t i o n . P r e n t i c e H a l l , New J e r s e y , p. 415. (104) B l a c k , P . J . a n d M.C. H e f f e r n a n . 1964. The A n a l y s i s o f t h e P r o t o n M a g n e t i c R e s o n a n c e S p e c t r a o f H e t e r o A r o m a t i c S y s t e m s . A u s t . J . Chem. 17:558. (105) A l b e r t , A. a n d G. C a t t e r a l . 1967. O x i d a t i v e R e p l a c e m e n t o f t h e H y d r a z i n o G r o u p by H y d r o g e n a n d D e u t e r i u m i n A z a n a p h t h a l e n e s . J . Chem. S o c . ( C ) , p. 1533. (106) P a s t o r , R., J . Musso a n d A. Cambon. 1973. D e t e r m i n i z a t i o n p a r RMN d e s D e n s i t e E l e c t r o n i q u e P i en S e r i e H e t e r o c y c l i q u e . I I - Q u i n o l a x i n e s e t Q u i n o l e i n e s . B u l l . S o c . Chim. F r a n c e , p. 3009. (107) Heywood, A., A. M a t h a i s a n d A.E. W i l l i a m s . 1970. I d e n t i f i c a t i o n o f S u l f o n i c A c i d s a n d S u l p h o n a t e s by Mass S p e c t r o m e t r y . A n a l . Chem. 4 2 ( 1 1 ) : 1 2 7 2 (108) G e l l e r s t e d t , G. and J . G i e r e r . 1972. The R e a c t i o n s o f L i g n i n D u r i n g N e u t r a l S u l p h i t e P u l p i n g . P a r t IV. A c t a Chem. S c a n d . 26:701. (109) G e l l e r s t e d t , G. a n d J . G i e r e r . 1970. The R e a c t i o n s o f L i g n i n D u r i n g N e u t r a l S u l p h i t e P u l p i n g P a r t I I I . A c t a Chem. S c a n d . 24:1654. 1 74 (110) D r a k e , N.L. 1942. The B u c h e r e r R e a c t i o n . O r g . R e a c t i o n s 1:105. (111) S c h o t e r , R. In " H o u b e n - W e y l - M u l l e r : M e t h o d e n d e r O r g a n i s h e n Chemie", IV. A u f l . G e o r g - T h i e m e - V e r l a g , S t u t t g a r t 1957, V o l . X I / I , p. 143. (112) Woroshtzow, N.N. and J.M. Kogan. 1932. Uber d i e E i n w i r k i n g d e r S c h w e f l i g e n S a u r e and I h r e r S a l z e a u f C h i n o l i n d e r i v a t e . B e r . 65:142. (113) F u c h s , W. and B. E i s n e r . 1920. Uber d i e T a u t o m e r i e d e r P h e n o l e , I I : R e s o r c i n . B e r . 53:886. (114) H a r t u n g , W.H., L . J . M i n n i c k and H.F. K o e h l e r . 1941. Some Amino A l k y l P h e n o l s . J . Am. Chem. S o c . 63:507. (115) F u c h s , W. and H. P i r a k . 1926. Uber d i e T a u t o m e r i e d e r P h e n o l e , V I I I : D i o x y - 1 , 2 - N a p h t h a l i n . B e r . 59:2454. (116) F u c h s , W. a n d F. N i s z e l . 1927. Uber d i e T a u t o m e r i e d e r P h e n o l e X : P h e n y l - H y d r a z i n und N a p h t h o l e d e r A l p h a - R i e h e . B e r . 60:209. (117) F u c h s , W. 1921. Uber d i e T a u t o m e r i e d e r P h e n o l e , I I I : B i s u l f i t und P h l o r a g l u c i n . B e r . 54:245. (118) R i e c h e , A. and H. S e e b o t h . 1960. E i g e n s c h a f t e n und S t r u k t u r Van Z w i s c h e n V e r b i n d u n g e n d e r B u c h e r e r - R e a k t i o n . L i e b i g s Ann. Chem. 638:43. (119) S e e b o t h , H. 1967. P r e p a r a t i v e Use o f i t s Chem. I n t . E d i t . E n g . The B u c h e r e r R e a c t i o n a n d t h e I n t e r m e d i a t e P r o d u c t s . Angew. 6 ( 4 ) : 3 0 7 . (120) R o b e r t s , J.D. and M.C. C a s e r i o . 1965. B a s i c P r i n c i p l e s o f O r g a n i c C h e m i s t r y . W.A. B e n j a m i n I n c . , New Y o r k , p. 441 . (121) Wheland, G.W. 1955. R e s o n a n c e i n O r g a n i c C h e m i s t r y . J . W i l e y and So n s , New Y o r k , p . 75. 175 (122) I b i d . , p. 98. (123) I b i d . , p. 404. (124) Cowdrey, W.A. and C.N. H i n s h e l w o o d . 1946. The Me c h a n i s m o f t h e B u c h e r e r R e a c t i o n . P a r t I The K i n e t i c s o f t h e C o n v e r s i o n o f N a p h t h y l a m i n e s i n t o N a p h t h o l s . J . Chem. S o c . , 1036. (125) Cowdrey, W.A. R e a c t i o n . P a r t N a p h t h i o n i c A c i d . 1946. The Mec h a n i s m o f t h e B u c h e r e r II I s o l a t i o n o f B i s u l p h i t e Compounds f r o m J .C.S., 1041. (126) Thomson, R.H. R e v i e w s 10:27. 1957 P h e n o l T a u t o m e r i s m . Q u a r t e r l y (127) Wheland, G.W. 1933. A C a l c u l a t i o n o f t h e E q u i l i b r i a i n K e t o - E n o l T a u t o m e r i s m . J.. Chem. P h y s . 1:731. (128) Nachod, F.C. 1938. K e t o - E n o l t a u t o m e r i e n i n L e i c h t e n und Schweren L o s u n g s m i t t e l n . Z. P h y s i k . Chem. A 182:193. (129) S c h w a r z e n b a c h , G. a n d C. W i t t w e r . 1947. The S t a t e o f E n o l i z a b l e K e t o n e s i n H i g h l y A c i d i c S o l v e n t s . H e l v . Chim. A c t a . 30:663. (130) Wheland, G.W. 1955. R e s o n a n c e i n O r g a n i c C h e m i s t r y . J . W i l e y and So n s , New Y o r k , p. 344. (131) CRC Handbook o f C h e m i s t r y a n d P h y s i c s , 5 5 t h E d i t i o n , 1974-1975, R.C. Weast E d . , CRC P r e s s , C l e v e l a n d , O h i o , p . E -64. (132) A l l a n , Z . J . , J . P o d s t a t a a n d Z. U r b a . 1969. E i n e Neue A r t Der B u c h e r e r - R e a k t i o n . A z o k u p p l u n g Auf P y r i d i n und B e s c h l e u n i g u n g Der N i t r i e r u n g von P y r i d i n . T e t r . L e t t e r s 55:4855. (133) C o t t o n , F.A. a n d G. W i l k i n s o n . 1972. A d v a n c e d I n o r g a n i c C h e m i s t r y . 3 r d E d . , J . W i l e y a n d Sons, New Y o r k , p. 448. 176 (134) R e i c h , L. and S.S. S t i v a l a . 1969. A u t o x i d a t i o n o f H y d r o c a r b o n s and P o l y o l e f i n s . M a r c e l D e k k e r I n c . , New Y o r k . (135) R o b e r t s , J.D. and M.C. C a s e r i o . 1965. B a s i c P r i n c i p l e s o f O r g a n i c C h e m i s t r y , W.A. B e n j a m i n I n c . , New Y o r k , p. 934. (136) J o h , T. and N. H a g i h a r a . 1967. P r e p a r a t i o n o f Q u i n o l i n e D e r i v a t i v e s f r o m S c h i f f Base and V i n y l E t h e r C a t a l y s e d by D i c o b a l t O c t a c a r b o n y 1 . T e t r . L e t t e r s , 4199. (137) F i e s e r , L . F . a n d M. F i e s e r . 1956. O r g a n i c C h e m i s t r y . T h i r d E d . , D.C. H e a t h and Co., B o s t o n , p. 716. (138) G r o b , C A . and P.W. S c h i e s s . 1967. H e t e r o l y t i c F r a g m e n t a t i o n . A C l a s s o f O r g a n i c R e a c t i o n s . Angew. Chem. I n t . E d i t . E n g . 6 ( 1 ) : 1 . (139) B e c k e r , K.B. a n d C A . G r o b . 1977. The F o r m a t i o n o f U n s a t u r a t e d G r o u p s by H e t e r o l y t i c F r a g m e n t a t i o n . I n " C h e m i s t r y o f D o u b l e - Bonded F u n c t i o n a l G r o u p s " . ' S. P a t a i e d . , J . W i l e y a n d S o n s , T o r o n t o , p. 653. (140) G r o b , C A . and W. Baumann. 1955. D i e 1 , 4 - E l i m i n i e r u n g u n t e r F r a g m e n t i e r u n g . H e l v . Chim. A c t a 38:594. (141) L a u e r , W.M. and C M . Langkammerer. 1934. The A c t i o n o f Sodium B i s u l p h i t e on R e s o r c i n o l . J . Am. Chem. S o c . 56:1628. (142) Crown Z e l l e r b a c h C o r p . A p p l i c a t i o n s f o r C a t e c h o l ; A Review o f t h e L i t e r a t u r e . 1973. C h e m i c a l P r o d u c t s D i v . , p. 2. (143) CRC Handbook o f C h e m i s t r y and P h y s i c s . 5 5 t h E d . , 1974-1975, R . C Weast E d . , CRC P r e s s , C l e v e l a n d , O h i o , p. B-72. (144) F o o , L.Y., G.W. McGraw a n d R.W. Hemingway. 1983. C o n d e n s e d T a n n i n s : P r e f e r e n t i a l S u b s t i t u t i o n a t t h e I n t e r f l a v a n o i d Bond by S u l p h i t e I o n . J . Chem. S o c . Chem. Commun. 12:672. 1 77 APPENDIX. S t a t i s t i c a l A n a l y s i s o f Q u a n t i t a t i v e Bond E v a l u a t i o n 1 78 I . V a r y i n g Amounts of Added B a r i u m H y d r o x i d e Amount Added Mean S h e a r S t r e n g t h Mean Wood F a i l u r e A= 30g 125 5.5 B= 40g 142 18.0 C= 50g 149 17.0 A. S h e a r S t r e n g t h ANOVA S o u r c e o f V a r i a t i o n SS DF Mean S q u a r e Computed F Column Means 3047 2 1523.5 1 .25 E r r o r 32850 27 1216.7 T o t a l 35897 29 F 0.05(2,27) = 3.35 > F ( c a l c . ) = 1.25 T h e r e f o r e , t h e r e i s no s i g n i f i c a n t d i f f e r e n c e i n t h e s h e a r s t r e n g t h s i n a d h e s i v e s made w i t h v a r y i n g amounts o f b a r i u m h y d r o x i d e a t t h e 0.05 l e v e l o f s i g n i f i c a n c e . 1 79 B. Wood F a i l u r e s ANOVA S o u r c e SS DF MS F Column Means 965 2 482.5 3.11 E r r o r 4192.5 27 155.28 T o t a l 5157.5 29 F 0.05(2,27) = 3.35 > F ( c a l c . ) = 3.11 T h e r e f o r e , t h e r e , i s no s i g n i f i c a n t d i f f e r e n c e i n t h e wood f a i l u r e means f o r a d h e s i v e s made w i t h v a r y i n g amounts o f b a r i u m h y d r o x i d e a t t h e 0.05 l e v e l o f s i g n i f i c a n c e . 1 80 11. A d h e s i v e s made w i t h Whole S o l u b l e R e a c t i o n - P r o d u c t M i x t u r e Amount o f Ammonium S u l f i t e U s e d Mean Shear, S t r e n g t h Mean Wood F a i l u r e A= 50g 137 12.5 , B= 40g 76 3 C= 20g 91 5.5 A. S h e a r S t r e n g t h s ANOVA S o u r c e SS DF MS F Column Means 20207 2 1 01 03 7.45 E r r o r 36640 27 1 357 T o t a l 56847 29 F 0.05(2,27) = 3.35 < P ( c a l c . ) = 7.45 T h e r e f o r e , a t l e a s t one mean i s d i f f e r e n t . 181 Duncan's M u l t i p l e Range Test Means: XB XC XA 76 91 137 p 2 3 Rp 2.888 3.035 Rp 33.6 35.4 At a l p h a = 0.05 XB XC XA (Any subset of a d j a c e n t means j o i n e d by a l i n e underneath are not s i g n i f i c a n t l y d i f f e r e n t ) 1 82 B. Wood F a i l u r e s A N O V A S o u r c e SS DF MS F Column Means 485 2 242.5 6.58 E r r o r 995 27 36.85 T o t a l 1480 29 F 0.05(2,27) = 3.35 < F ( c a l c . ) = 6.58 T h e r e f o r e , a t l e a s t one mean i s d i f f e r e n t . 183 Duncan's Multiple Range Test Means: XB XC XA 3.0 5.5 12.5 p 2 3 Rp 2.888 . 3.035 Rp 5.54 5.83 at alpha = 0.05 XC XB XA 1 84 I I I . V a r y i n g G l u e l i n e L o a d i n g L o a d i n g ( g / l 0 0 c m 2 , s i n g l e g l u e l i n e ) S.S. Mean W.F. Mean A B C D 2.71 2.33 1 .94 1 .55 200 208 190 130 23 45 70 45 A . S h e a r S t r e n g t h A N O V A S o u r c e SS DF MS F Column Means 7485 3 2495 1 19 E r r o r 63 3 21 T o t a l 7547 • F 0.05(3,3) = 9.28 < F ( c a l c . ) = 119 T h e r e f o r e , a t l e a s t one mean i s d i f f e r e n t . 185 Duncan's M u l t i p l e Range T e s t Means: L XD XC XA XB 130 190 200 208 p 2 3 4 Rp 4.501 4.516 4.516 Rp 14.58 14.63 14.63 a t a l p h a = 0.05 XD XC XA XB 1 8 6 B. Wood F a i l u r e s ANOVA S o u r c e SS DF MS F Column Means 2260 3 753 2.48 E r r o r 913 3 304 T o t a l 3172 F 0.05(3,3) = 9.28 > F ( c a l c . ) = 2.48 T h e r e f o r e , t h e r e i s no s i g n i f i c a n t d i f f e r e n c e i n t h e means. 187 IV. V a r y i n g P a r a f o r m a l d e h y d e C o n t e n t Grams o f P a r a f o r m a l d e h y d e i n 5.9g of A d h e s i v e S.S. Means A B C D 0.5 0.4 0.3 0.2 83 1 68 1 68 220 W.F. Means 25 ~ 65 40 60 A. S h e a r S t r e n g t h ANOVA S o u r c e SS DF MS F Column Means 19435 3 6478 39.99 E r r o r 487 3 162 T o t a l 1 9922 F 0.05(3,3) = 9.28 < F ( C a l c . ) = 39.99 T h e r e f o r e , a t l e a s t one mean i f d i f f e r e n t . 188 Duncan's M u l t i p l e Range T e s t Means: XA XB XC XD 83 168 168 220 p 2 3 4 Rp 4.501 4.516 4.516 Rp 40.51 40.64 40.64 a t a l p h a = 0,05 XA XB XC XD 189 B. Wood F a i l u r e ANOVA Source SS DF MS F Column Means 2050 3 683 6.83 Error 300 3 100 Total 2350 F 0.05(3,3) = 9.28 > F(calc.) = 6.83 Therefore, there i s no s i g n i f i c a n t difference in the means. 

Cite

Citation Scheme:

        

Citations by CSL (citeproc-js)

Usage Statistics

Share

Embed

Customize your widget with the following options, then copy and paste the code below into the HTML of your page to embed this item in your website.
                        
                            <div id="ubcOpenCollectionsWidgetDisplay">
                            <script id="ubcOpenCollectionsWidget"
                            src="{[{embed.src}]}"
                            data-item="{[{embed.item}]}"
                            data-collection="{[{embed.collection}]}"
                            data-metadata="{[{embed.showMetadata}]}"
                            data-width="{[{embed.width}]}"
                            async >
                            </script>
                            </div>
                        
                    
IIIF logo Our image viewer uses the IIIF 2.0 standard. To load this item in other compatible viewers, use this url:
https://iiif.library.ubc.ca/presentation/dsp.831.1-0096577/manifest

Comment

Related Items