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The Surface catalyzed racemization of 1, 1’-Binaphthyl Hutchins, Lawrence Guy 1980

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THE SURFACE CATALYZED RACEMIZATION OF 1,1'-BINAPHTHYL by LAWRENCE GUY HUTCHINS B.A. (magna cum l a u d e ) , U n i v e r s i t y o f W i s c o n s i n - M i l w a u k e e , 1975 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY i n THE FACULTY OP GRADUATE STUDIES IN CHEMISTRY We a c c e p t t h i s t h e s i s as co n f o r m i n g t o the r e q u i r e d s t a n d a r d THE UNIVERSITY OF BRITISH COLUMBIA September, 1979 Lawrence Guy Hutchins, 1980 In presenting th is thes is in p a r t i a l fu l f i lment of the requirements for an advanced degree at the Univers i ty of B r i t i s h Columbia, I agree that the L ibrary sha l l make i t f ree ly ava i lab le for reference and study. I fur ther agree that permission for extensive copying of this thesis for scho la r ly purposes may be granted by the Head of my Department or by his representat ives . It is understood that copying or publication of th is thes is for f i nanc ia l gain sha l l not be allowed without my writ ten permission. Department of The Univers i ty of B r i t i s h Columbia 2075 Wesbrook P l a c e V a n c o u v e r , Canada V6T 1W5 Date / / O L A ^ O ^ V ^ 3a, i i ABSTRACT S u p e r v i s o r : Dr. R.E. P i n c o c k The s u r f a c e c a t a l y z e d r a c e m i z a t i o n o f a s i m p l e o r g a n i c r e a c t i o n - the r a c e m i z a t i o n o f 1 , 1 1 - b i n a p h t h y l - has been s t u d i e d u s i n g c a r b o n , Raney N i c k e l , and p l a t i n u m (Adams' C a t a -l y s t ) as s o l i d c a t a l y s t s . In each case the r a t e o f the c a t a l y z e d r e a c t i o n was s t u d i e d u s i n g p o l a r i m e t r i c methods. The dependence of the r a t e on v a r i o u s parameters was then used t o determine f e a t u r e s o f the c a t a l y z e d r e a c t i o n s . In the case o f the carbon c a t a l y z e d r e a c t i o n , 4 , 4 ' - d i s u b -s t i t u t e d - 1 , 1 ' - b i n a p h t h y l s were s y n t h e s i z e d and t h e i r c a t a l y z e d r e a c t i o n r a t e s d e t e r m i n e d . A l l the r e a c t i o n s f o l l o w e d smooth f i r s t o r d e r k i n e t i c s . U s i n g a Hammett (a^) p l o t f o r the c a t a -l y z e d and u n c a t a l y z e d r e a c t i o n s , c a t a l y s i s was found t o proceed by way o f e l e c t r o n d o n a t i o n i n t o the b i n a p h t h y l r i n g system. O x i d a t i o n or r e d u c t i o n o f the c a t a l y s t , which would modify d i s -o r g a n i z e d a r e a s on the s u r f a c e , had no e f f e c t on i t s a c t i v i t y . H a l o g e n a t i o n o f the c a t a l y s t , which i s b e l i e v e d t o occur on the o r g a n i z e d b a s a l p l a n e s o f the c a r b o n , d r a m a t i c a l l y i n c r e a s e d i t s a c t i v i t y and l e d t o new s o l v e n t e f f e c t s . The e f f e c t o f h a l o g e n -a t i o n was e x p l a i n e d by c o n s i d e r i n g chemisorbed s o l v e n t m o l e c u l e s t o be a type o f i n h i b i t o r whose d e s o r p t i o n r a t e i s i n c r e a s e d when the s i t e s of a d s o r p t i o n (the b a s a l p l a n e s ) are d i s r u p t e d by bound h a l o g e n . A p o t a s s i u m - g r a p h i t e i n t e r c a l a t e was used as a model f o r the carbon s u r f a c e and l e d t o the c o n c l u s i o n t h a t carbon c a t a l y s i s may i n v o l v e the f o r m a t i o n o f the r a d i c a l a n i o n o f 1 , 1 ' b i n a p h t h y l on the b a s a l p l a n e s o f the carbon s u r f a c e . Raney N i c k e l c a t a l y z e d both the r a c e m i z a t i o n and the r e - , d u c t i o n o f 1 , 1 ' - b i n a p h t h y l . In a d d i t i o n , an e x t e n s i v e a d s o r p -t i o n p r o c e s s o c c u r r e d . These t h r e e i n t e r a c t i o n s c o u l d be con-t r o l l e d i n d e p e n d e n t l y by c a r e f u l p o i s o n i n g w i t h e l e m e n t a l s u l f u r or d o d e c a n e t h i o l . T h i s suggested t h a t t h e r e were t h r e e d i f f e r -ent types o f s u r f a c e s i t e s on Raney N i c k e l , each r e s p o n s i b l e f o r a s i n g l e type o f i n t e r a c t i o n w i t h 1 , 1 ' - b i n a p h t h y l . A l s o , i t a l l o w e d the t h r e e p r o c e s s e s t o be s t u d i e d i n d e p e n d e n t l y . The r e d u c t i o n proceeded through t h r e e i n t e r m e d i a t e s t o g i v e 5 , 6 , 7 , 8 , 5 ' , 6 ' , 7 1 , 8 1 - o c t a h y d r o - 1 , 1 ' - b i n a p h t h y l as the f i n a l p r o d u c t . NMR s t u d i e s showed t h i s m o l e c u l e t o e x i s t as two enantiomers which c o u l d i n t e r c o n v e r t a t a slow r a t e ( t ^ = 17 hr) The r a c e m i z a t i o n p r o c e s s showed good f i r s t o r d e r k i n e t i c p l o t s a f t e r an i n i t i a l c u r v e d p o r t i o n . The c u r v e d p o r t i o n o f the p l o t s i s due to the c o n c u r r e n t a d s o r p t i o n p r o c e s s . Problems of r e p r o d u c i b i l i t y hampered f u r t h e r k i n e t i c s t u d i e s . The ad-s o r p t i o n p r o c e s s showed a Langmuir-type a d s o r p t i o n i s o t h e r m , as w e l l as an a d s o r p t i o n i s o b a r and k i n e t i c s which are t y p i c a l o f o t h e r slow c h e m i s o r p t i o n s . The p l a t i n u m (Adams' c a t a l y s t ) c a t a l y z e d r a c e m i z a t i o n o f 1 , 1 ' - b i n a p h t h y l a l s o showed good f i r s t o r d e r k i n e t i c s . The i v o b served r a t e c o n s t a n t , k ^ r was i n v e r s e l y p r o p o r t i o n a l t o the c o n c e n t r a t i o n o f s u b s t r a t e . The r e a c t i o n r a t e was a l s o i n d e -pendent o f the c o n c e n t r a t i o n o f the c a t a l y s t . T h i s p e c u l i a r k i n e t i c e f f e c t c o u l d not be accounted f o r by the i n t e r v e n t i o n o f d i f f u s i o n - c o n t r o l l e d p r o c e s s e s and remains u n e x p l a i n e d . The p o i s o n i n g e f f e c t o f a i r and the i n h i b i t o r y e f f e c t o f c y c l o h e x e n e and c y c l o h e x a n e i n d i c a t e t h a t r e d u c t i o n and r a c e m i z a t i o n o ccur on the same s i t e . C o n t i n u e d s t u d i e s were not p o s s i b l e because of an u n c o n t r o l l a b l e d e c r e a s e i n c a t a l y s t a c t i v i t y . V TABLE OF CONTENTS I . I n t r o d u c t i o n 1 I I . The Carbon C a t a l y z e d R a c e m i z a t i o n o f 1 , 1 ' - B i n a p h t h y l 15 A. I n t r o d u c t i o n 15 B. S y n t h e s i s o f 4 , 4 1 - D i s u b s t i t u t e d 1 , 1 ' - B i n a p h t h y l s 24 C. Carbon C a t a l y z e d R a c e m i z a t i o n o f S u b s t i t u t e d B i n a p h t h y l s 27 D. The E f f e c t o f O x i d a t i o n and R e d u c t i o n on the C a t a l y t i c A c t i v i t y o f Carbons 35 E. The E f f e c t o f C h l o r i n a t i o n and B r o m i n a t i o n on the A c t i v i t y o f Carbons 38 F. S o l v a t e d E l e c t r o n C a t a l y z e d R a c e m i z a t i o n o f 1 , 1 ' - B i n a p h t h y l 45 G. G r a p h i t e I n t e r c a l a t e C a t a l y z e d R a c e m i z a t i o n o f 1 , 1 ' - B i n a p h t h y l 50 H. C o n c l u s i o n 55 I I I . The I n t e r a c t i o n o f Racemic and O p t i c a l l y A c t i v e 1 , 1 ' - B i n a p h t h y l w i t h Raney N i c k e l 57 A. I n t r o d u c t i o n 57 B. R e d u c t i o n o f Racemic 1 , 1 ' - B i n a p h t h y l w i t h Raney N i c k e l 61 C. The Spontaneous R e s o l u t i o n o f 5,6,7,8,5',6',7',8'-O c t a h y d r o - 1 , 1 ' - B i n a p h t h y l 72 D. Treatment o f O p t i c a l l y A c t i v e 1 , 1 ' - B i n a p h t h y l w i t h Raney N i c k e l 76 E. Treatment o f O p t i c a l l y A c t i v e 1 , 1 ' - B i n a p h t h y l w i t h P o i s o n e d Raney N i c k e l 80 F. The P o i s o n e d Raney N i c k e l C a t a l y z e d R a c e m i z a t i o n o f 1 , 1 1 - B i n a p h t h y l 82 v i TABLE OF CONTENTS (co n t i n u e d ) G. The A d s o r p t i o n o f Racemic 1 , 1 1 - B i n a p h t h y l on P o i s o n e d Raney N i c k e l 92 H. C o n c l u s i o n 97 IV. The P l a t i n u m (Adams' C a t a l y s t ) C a t a l y z e d R a c e m i z a t i o n o f 1 , 1 ' - B i n a p h t h y l 101 A. I n t r o d u c t i o n 101 B. The P l a t i n u m C a t a l y z e d R a c e m i z a t i o n o f 1 , 1 ' - B i n a p h t h y l 104 C. The Dependence o f the C a t a l y z e d Rate on 1 , 1 1 - B i n a p h t h y l and P l a t i n u m C o n c e n t r a t i o n s 108 D. The E f f e c t o f Oxygen, C y c l o h e x e n e , and C y c l o -hexane on the P l a t i n u m C a t a l y z e d R a c e m i z a t i o n of 1 , 1 ' - B i n a p h t h y l 114 E. The Loss i n C a t a l y t i c A c t i v i t y 119 F. C o n c l u s i o n 121 V. E x p e r i m e n t a l 123 B i b l i o g r a p h y 146 v i i LIST OF TABLES Table I Oxides on Carbon. 21 Table I I N o r i t SGI C a t a l y s i s o f V a r i o u s S u b s t r a t e s . 28 Table I I I E f f e c t o f O x i d a t i o n and R e d u c t i o n on the C a t a l y t i c A c t i v i t y o f Carbon C a t a l y s t s . 37 Table IV E f f e c t o f C h l o r i n a t i o n and B r o m i n a t i o n on the C a t a l y t i c A c t i v i t y o f Spheron 6. 40 Table V The E f f e c t o f S o l v e n t on k Q b s f o r Brominated Spheron 6. 41 Table VI R e s u l t s o f T r e a t i n g a S o l u t i o n o f O p t i c a l l y A c t i v e B i n a p h t h y l w i t h Raney N i c k e l f o r 115 m i n u t e s . 77 Table V I I The E f f e c t o f S u l f u r on the A c t i v i t y o f Raney N i c k e l . 81 Table V I I I T a b u l a t e d K i n e t i c R e s u l t s f o r the P o i s o n e d Raney N i c k e l C a t a l y z e d R a c e m i z a t i o n o f B i n a p h t h y l . 89 v i i i LIST OF FIGURES F i g u r e 1 F i g u r e 2 F i g u r e 3 F i g u r e 5 F i g u r e 6 F i g u r e 7 F i g u r e 8 F i g u r e 9 F i g u r e 10 F i g u r e 11 F i g u r e 12 F i g u r e 13 The S t r u c t u r e o f G r a p h i t e . The S t r u c t u r e o f Carbon B l a c k s . F i r s t Order K i n e t i c P l o t s f o r U n c a t a l y z e d R a c e m i z a t i o n o f S u b s t i t u t e d B i n a p h t h y l s i n CHC1 3 a t 23.8 'C. F i g u r e 4 F i r s t Order K i n e t i c P l o t s f o r N o r i t SGI C a t a l y z e d R a c e m i z a t i o n o f S u b s t i t u t e d B i n a p h t h y l s i n CHC1 3 a t 23.8 °C. The E f f e c t o f Impure DNB on the N o r i t SGI C a t a l y z e d R a c e m i z a t i o n o f B i n a p h t h y l i n CHC1 3 a t 23.: C. Hammett P l o t f o r U n c a t a l y z e d and N o r i t SGI C a t a l y z e d R a c e m i z a t i o n o f S u b s t i t u t e d B i n a p h t h y l s . a v e r s u s Time f o r the S o l v a t e d E l e c t r o n C a t a l y z e d R a c e m i z a t i o n o f B i n a p h t h y l . F i r s t Order K i n e t i c P l o t s f o t the S o l v a t e d E l e c t r o n C a t a l y z e d R a c e m i z a t i o n o f B i n a p h t h y l . F i r s t Order K i n e t i c P l o t f o r the P o t a s s i u m -G r a p h i t e I n t e r c a l a t e C a t a l y z e d R a c e m i z a t i o n o f B i n a p h t h y l i n n-Heptane a t 40.0 C. F i r s t Order K i n e t i c P l o t f o r the F e C l 3 ~ G r a p h i t e I n t e r c a l a t e C a t a l y z e d R a c e m i z a t i o n o f B i n a p h t h y l i n n-Heptane a t 25.0 C. Pr o d u c t D i s t r i b u t i o n Curves o f the I n t e r -mediates i n the R e d u c t i o n o f B i n a p h t h y l 270 MHZ NMR o f 5 ,6,7,8,5 1,6',7',8'-Octahydro-1,1' - b i n a p h t h y l S t r u c t u r e and 270 MHZ NMR Assignments o f 5,6,7,8,5',6',7',8'-Octahydro-1,1'-b i n a p h t h y l 17 17 29 30 32 34 47 48 52 54 64 70 71 i x LIST OF FIGURES (continued) F i g u r e 14 F i r s t Order K i n e t i c P l o t s f o r the P o i s o n e d Raney N i c k e l C a t a l y z e d R a c e m i z a t i o n o f B i n a p h t h y l i n n-Heptane a t 25.0 °C. 84 F i g u r e 15 F i r s t Order K i n e t i c P l o t and F r a c t i o n Adsorbed f o r the P o i s o n e d Raney N i c k e l C a t a l y z e d R a c e m i z a t i o n o f B i n a p h t h y l 85 F i g u r e 16 The E f f e c t on the F i r s t Order K i n e t i c P l o t o f P r e t r e a t i n g P o i s o n e d Raney N i c k e l w i t h B i n a p h t h y l 87 F i g u r e 17 Moles Adsorbed v e r s u s Time f o r the A d s o r p t i o n o f B i n a p h t h y l on P o i s o n e d Raney N i c k e l 93 F i g u r e 18 A d s o r p t i o n Isotherm f o r B i n a p h t h y l on Po i s o n e d Raney N i c k e l 94 F i g u r e 19 A d s o r p t i o n I s o b a r f o r B i n a p h t h y l on Po i s o n e d Raney N i c k e l 96 F i g u r e 20 F i r s t Order K i n e t i c P l o t f o r the P l a t i n u m C a t a l y z e d R a c e m i z a t i o n o f B i n a p h t h y l 105 F i g u r e 21 F i r s t Order K i n e t i c P l o t f o r the P l a t i n u m C a t a l y z e d R a c e m i z a t i o n o f B i n a p h t h y l U s i n g Time o f R e d u c t i o n as the Time A x i s 107 F i g u r e 22 Dependence o f k ^ ^ on B i n a p h t h y l C o n c e n t r a -t i o n f o r the P l a t i n u m C a t a l y z e d R a c e m i z a t i o n o f B i n a p h t h y l 109 F i g u r e 23 Dependence o f k 0j-, s on P l a t i n u m C o n c e n t r a t i o n f o r the P l a t i n u m C a t a l y z e d R a c e m i z a t i o n o f B i n a p h t h y l 1 1 1 F i g u r e 24 E f f e c t o f A i r on the F i r s t Order K i n e t i c P l o t f o r the P l a t i n u m C a t a l y z e d R a c e m i z a t i o n o f B i n a p h t h y l 115 F i g u r e 25 E f f e c t o f Cyclohexene on the F i r s t Order K i n e t i c P l o t f o r the P l a t i n u m C a t a l y z e d R a c e m i z a t i o n o f B i n a p h t h y l 116 F i g u r e 26 E f f e c t o f Cyclohexane on the F i r s t Order K i n e t i c P l o t f o r the P l a t i n u m C a t a l y z e d R a c e m i z a t i o n o f B i n a p h t h y l 118 X ACKNOWLEDGEMENTS I would l i k e t o extend my s i n c e r e g r a t i t u d e t o Dr. R i c h a r d E. P i n c o c k f o r the i n t e r e s t , s u p p o r t , and encouragement he has shown throughout t h i s r e s e a r c h . I would a l s o l i k e t o thank my w i f e , J e s s i c a , and d a u g h t e r , Leah, f o r showing t h e i r l o v e , p a t i e n c e , and u n d e r s t a n d i n g d u r i n g the c o u r s e of t h i s work. T h i s t h e s i s i s d e d i c a t e d t o them. The s t a f f , s t u d e n t s , and t e c h n i c i a n s o f the C h e m i s t r y Department a t the U n i v e r s i t y o f B r i t i s h Columbia have p r o v i d e d innumerable d i s c u s s i o n s , equipment, s e r v i c e s , and, most o f a l l , f r i e n d s h i p t hroughout t h i s work. I remain most g r a t e f u l . I would l i k e t o e x p r e s s my a p p r e c i a t i o n t o P a t r i c i a G r a b i f o r her v e r y f i n e and e f f i c i e n t t y p i n g . F i n a l l y , I would l i k e t o thank the U n i v e r s i t y o f B r i t i s h Columbia Graduate F e l l o w s h i p Fund f o r p r o v i d i n g f i n a n c i a l a s s i s t a n c e t hroughout t h i s work. 1 I . INTRODUCTION Much o f what i s known o f the mechanisms o f heterogeneous c a t a l y s i s has been o b t a i n e d by the st u d y o f c a t a l y z e d h y dro-g e n a t i o n r e a c t i o n s , p a r t i c u l a r l y i n the gas phase. T h i s t h e s i s i s concerned w i t h the s u r f a c e c a t a l y s i s of a s i m p l e o r g a n i c r e a c t i o n which i s not a h y d r o g e n a t i o n r e a c t i o n : the r a c e m i z a -t i o n o f 1 , 1 1 - b i n a p h t h y l . Each o f the t h r e e f o l l o w i n g c h a p t e r s i s concerned w i t h the c a t a l y s i s o f t h i s s i m p l e r e a c t i o n by one of t h r e e d i f f e r e n t s o l i d s - c a r b o n , Raney N i c k e l , or p l a t i n u m -and w i l l i n c l u d e a d e s c r i p t i o n o f the p e r t i n e n t f e a t u r e s o f each c a t a l y s t . B e f o r e d e s c r i b i n g the m o l e c u l e 1 , 1 ' - b i n a p h t h y l , and b e f o r e r e v i e w i n g what i s b e l i e v e d t o be i t s mechanism f o r the u n c a t a l y z e d r a c e m i z a t i o n r e a c t i o n , i t i s a p p r o p r i a t e t o r e v i e w some f e a t u r e s o f heterogeneous c a t a l y s i s as i t a p p l i e s t o o r -g a n i c r e a c t i o n s . A c a t a l y s t i s a subst a n c e which i n c r e a s e s the r a t e o f a c h e m i c a l r e a c t i o n w i t h o u t i t s e l f b e i n g consumed. J u s t l i k e the r e a c t i o n s they c a t a l y z e , c a t a l y s t s themselves may be c l a s s i f i e d as e i t h e r homogeneous or heterogeneous. With a homogeneous c a t a l y s t both the c a t a l y s t and the r e a c t a n t m o l e c u l e s ( s u b s t r a t e ) are p r e s e n t i n the same phase. In the case o f heterogeneous c a t a l y s t s , r a t e enhancements are brought about by the presence of an i n t e r f a c e between two phases. T y p i c a l l y , the two phases V c o n s i s t o f a s o l i d c a t a l y s t and a r e a c t a n t gas or a s o l i d and e i t h e r a r e a c t a n t l i q u i d or a s o l u t i o n i n which the r e a c t a n t -e i t h e r a s o l i d , l i q u i d , or gas - i s d i s s o l v e d . 2 Another type o f heterogeneous c a t a l y s i s which i s r e c e i v i n g i n c r e a s i n g a t t e n t i o n i s m i c e l l a r c a t a l y s i s , i n which the two phases o f co n c e r n are both l i q u i d s . T h i s d i s c u s s i o n w i l l o n l y be concerned w i t h heterogeneous c a t a l y s i s i n v o l v i n g s o l i d s and w i l l not i n c l u d e m i c e l l a r type c a t a l y s t s . In any heterogeneous c a t a l y t i c system t h e r e are s e v e r a l d i f f e r e n t s t e p s through which a r e a c t a n t m o l e c u l e ( s ) must pass d u r i n g i t s t r a n s f o r m a t i o n i n t o a p r o d u c t m o l e c u l e ( s ) . The p r e -c i s e number o f s t e p s w i l l depend on the system o f c o n c e r n and the number of. r e a c t a n t s and p r o d u c t s . In the s i m p l e s t c a s e , gaseous A r e a c t s t o form gaseous B i n a r e a c t i o n c a t a l y z e d by a s o l i d S. A f t e r A e n t e r s the c a t a -l y t i c system i t must f i r s t d i f f u s e through the gas phase t o the s u r f a c e o f S. S i n c e most p r a c t i c a l c a t a l y s t s have a porous s t r u c t u r e which p e r m i t s a c c e s s t o a l a r g e r s u r f a c e a r e a of the s o l i d , A must then d i f f u s e through the pores t o the s i t e o f c a t a l y s i s on the s u r f a c e (the a c t i v e s i t e ) . There the r e a c t i o n o f A t o B o c c u r s i n one or s e v e r a l s t e p s . F o l l o w i n g the forma-t i o n o f B, i t must d i f f u s e away from the s u r f a c e i n the r e v e r s e f a s h i o n as A. In more c o m p l i c a t e d c ases t h e r e may be s e v e r a l r e a c t a n t or p r o d u c t m o l e c u l e s i n v o l v e d . Each m o l e c u l e must then undergo the v a r i o u s p r o c e s s e s d e s c r i b e d above i n o r d e r t o a c h i e v e e f -f e c t i v e c a t a l y s i s . For a l i q u i d - s o l i d system the same a n a l y s i s c o u l d be a p p l i e d . However i f a gaseous r e a c t a n t must f i r s t e n t e r the l i q u i d b e f o r e d i f f u s i n g t o the bulk s o l i d , then an 3 a d d i t i o n a l s t e p t o be c o n s i d e r e d would be the d i f f u s i o n o f the gas a c r o s s the g a s - l i q u i d i n t e r f a c e . C o m p l e t e l y u n d e r s t a n d i n g how a c a t a l y s t c a t a l y z e s a p a r -t i c u l a r r e a c t i o n would i n v o l v e knowing the e x t e n t and importance o f each o f the s e v e r a l s t e p s f o r a l l r e a c t a n t s and p r o d u c t s d u r i n g the c o u r s e o f the r e a c t i o n . N e e d l e s s t o say, t h i s f o r -m idable t a s k has y e t t o be a c h i e v e d . N e v e r t h e l e s s , a g r e a t d e a l o f i n f o r m a t i o n has been c o l l e c t e d f o r a v a r i e t y o f h e t e r o -geneous c a t a l y z e d r e a c t i o n s . E x a c t l y what type o f i n f o r m a t i o n i s o b t a i n e d i s determined t o a l a r g e e x t e n t by the method used t o study the r e a c t i o n . K i n e t i c methods are u s e f u l i n d e t e r m i n i n g the number of s t e p s i n a g i v e n r e a c t i o n and a l s o i n d e t e r m i n i n g which s t e p or s t e p s i n the c a t a l y t i c p r o c e s s may be r a t e - d e t e r m i n i n g . To i l -l u s t r a t e the e f f e c t i v e n e s s o f the k i n e t i c approach, c o n s i d e r the e s s e n t i a l l y i r r e v e r s i b l e r e a c t i o n A ( g ) + B ( g ) c a t a l y s t * C ( g ) i n which a l l a d s o r p t i o n s o f r e a c t a n t s and p r o d u c t s are a t e q u i l -i b r i u m and none o f the d i f f u s i o n s t e p s are r a t e - l i m i t i n g . I f the r a t e - d e t e r m i n i n g s t e p i s the r e a c t i o n o f two s t r o n g l y ad-sorbed m o l e c u l e s A and B, then the r e a c t i o n r a t e f o l l o w s Lang-105 * muir-Hinshelwood k i n e t i c s : ' T h i s a l s o assumes a Langmuir a d s o r p t i o n i s o t h e r m f o r r e -a c t a n t s and p r o d u c t s (see b e l o w ) . 4 dc k b A b B P A P B r a t e = d t = 2 (1 + b A P A + b B P B ) (Langmuir-Hinshelwood k i n e t i c s ) where b A , b B , and k are constants c h a r a c t e r i s t i c of the system and P A and P B are the pressure of A and B, r e s p e c t i v e l y . I f o n l y A i s adsorbed on the s u r f a c e and the r a t e - d e t e r m i n -ing step i s the r e a c t i o n of s t r o n g l y adsorbed A with gaseous B, 105 then the r e a c t i o n would f o l l o w a type of R i d e a l - E l e y mechanism, fo r which the rat e e x p r e s s i o n i s , kb-P^P^ dc A A B r a t e dt " 1 + b A P A ( R i d e a l - E l e y mechanism) and k, b A , P A, and P B are d e f i n e d as above. The two mechanisms may thus be d i s t i n g u i s h e d on the b a s i s of t h e i r r a t e expres-s i o n s . Another approach to studying s u r f a c e c a t a l y z e d r e a c t i o n s i s to determine how the r e a c t i o n r a t e or product(s) change with the s t r u c t u r e and e l e c t r o n i c c h a r a c t e r of the c a t a l y s t . T h i s approach has been s u c c e s s f u l l y a p p l i e d by Beeck''"^ to the hydro-genation of ethylene by t r a n s i t i o n metal c a t a l y s t s . Beeck found t h a t the most a c t i v e c a t a l y s t f o r ethylene hydrogenation ( r h o d i -um) had the g r e a t e s t amount of (percentage) d-character and an o i n t e r a t o m i c l a t t i c e spacing of 3.75 A. These, presumably, were the i d e a l c h a r a c t e r i s t i c s f o r the a c t i v e s i t e f o r ethylene ad-s o r p t i o n . 5 The s t e r e o c h e m i s t r y o f the p r o d u c t ( s ) and the v a r i a t i o n of p r o d u c t s w i t h r e a c t a n t s t e r e o c h e m i s t r y p r o v i d e s another t o o l 65 f o r a n a l y z i n g c a t a l y z e d r e a c t i o n s . For example, the h y d r o -10 7 108 g e n a t i o n o f s u b s t i t u t e d a l k e n e s and a c e t y l e n e s ' c l e a r l y i n d i c a t e s t h a t , because o n l y c i s a d d i t i o n o f hydrogen o c c u r s , both hydrogens must add from the same f a c e o f the m o l e c u l e . Thus the m o l e c u l e does not desorb a f t e r the a d d i t i o n o f one hydrogen and r e a d s o r b on the o p p o s i t e f a c e t o add the second hydrogen. One o f the most p o w e r f u l methods f o r s t u d y i n g a r e a c t i o n c a t a l y z e d by a heterogeneous c a t a l y s t has i n v o l v e d the use o f 109 110 i s o t o p e s . ' Methods u s i n g i s o t o p i c t r a c e r s have been used t o s t u d y the n a t u r e o f adsorbed s p e c i e s , t o i d e n t i f y r a t e de-t e r m i n i n g s t e p s , and t o study s t e r e o c h e m i c a l changes d u r i n g the c o u r s e o f a r e a c t i o n , t o name j u s t a few a p p l i c a t i o n s . One o f the more i n t e r e s t i n g i n v e s t i g a t i o n s has been Bur-w e l l ' s e x a m i n a t i o n o f d e u t e r i u m d i s t r i b u t i o n d u r i n g the hydrogen exchange r e a c t i o n o f c y c l o p e n t a n e on t r a n s i t i o n m e t a l c a t a -l o g l y s t s . B u r w e l l found t h a t , a f t e r a s h o r t exposure o f gaseous c y c l o p e n t a n e t o a t r a n s i t i o n m e t a l s u r f a c e c o v e r e d w i t h d e u t e r -ium, an e x c e s s o f the C^H^D^ isomer appeared i n the gas phase. He used t h i s as e v i d e n c e t h a t the c y c l o p e n t a n e has an extended r e s i d e n c e time on the s u r f a c e , a f t e r which i t 'tumbles' over t o exchange the hydrogens on i t s o t h e r s i d e . A g r e a t d e a l of i n s i g h t i n t o the mechanism of heterogeneous c a t a l y s i s has been g a i n e d by s t u d y i n g the n a t u r e of the m o l e c u l e 6 or molecules adsorbed on the s u r f a c e . There are roughly two types of a d s o r p t i o n which might occur. The f i r s t type i n v o l v e s formation of chemical compounds on the s u r f a c e , with a heat of a d s o r p t i o n u s u a l l y i n the order of 10 kcal/mole or h i g h e r , and i s termed ch e m i s o r p t i o n . The second type of a d s o r p t i o n i n v o l v e s f o r c e s o f a t t r a c t i o n which are s i m i l a r to those o c c u r r i n g during condensation and heats of a d s o r p t i o n are c o r r e s p o n d i n g l y l e s s than those i n chemisorption, u s u a l l y l e s s than 10 kcal/mole. T h i s l a t t e r type of a d s o r p t i o n i s termed p h y s i s o r p t i o n . The two types of a d s o r p t i o n mentioned here are a c t u a l l y the l i m i t i n g extremes for the i n t e r a c t i o n of an adsorbate with an adsorbent and c l a s s i f i c a t i o n of a p a r t i c u l a r system as e i t h e r chemisorp-t i o n or p h y s i s o r p t i o n i s not always a p p r o p r i a t e . I t should be remembered, however, that a whole spectrum of a d s o r p t i v e bonds may occur. An a d s o r p t i o n isotherm shows how the amount adsorbed de-pends on the e q u i l i b r i u m pressure (or c o n c e n t r a t i o n ) at a given temperature. The isotherm i s the best method of d e s c r i b i n g an a d s o r p t i o n e q u i l i b r i u m . There are, i n g e n e r a l , f i v e d i f f e r -70 ent types of a d s o r p t i o n isotherms, each one with i t s own s e t of assumptions regarding the adsorbent s u r f a c e . For example, a Langmuir p l o t of the amount adsorbed, q, versus e q u i l i b r i u m p r e s s u r e , P, shows q a s y m p t o t i c a l l y approaching a maximum v a l u e . Ey c o n t r a s t , a F r e u n d l i c h isotherm g i v e s a r i s i n g curve with an i n f l e c t i o n p o i n t . P r e s s u r e Langmuir-type i s o t h e r m P r e s s u r e F r e u n d l i c h - t y p e i s o t h e r m The reason f o r the d i f f e r e n t c u r v e s i s t h a t the Langmuir d e r i v a t i o n assumes: 1) t h a t the a d s o r b a t e i s adsorbed l o c a l l y on an a d s o r p t i o n s i t e ; 2) each s i t e adsorbs o n l y one a d s o r b a t e m o l e c u l e ; and 3) the energy o f a d s o r p t i o n i s the same a t each s i t e and independent o f the o t h e r s i t e s . With these assumptions the e x p r e s s i o n f o r q, the amount adsorbed, becomes q bP - m  q " 1 + bP where q m i s the amount adsorbed a t monolayer c o v e r a g e , P i s the e q u i l i b r i u m p r e s s u r e , and b i s the r a t i o o f a d s o r p t i o n and de-s o r p t i o n r a t e c o n s t a n t s . The F r e u n d l i c h i s o t h e r m , on the o t h e r hand, assumes a l o g a r i t h m i c f a l l i n the energy o f a d s o r p t i o n as a f u n c t i o n o f 8 s u r f a c e coverage. T h i s leads to the f o l l o w i n g e x p r e s s i o n f o r q q = k P 1 / n where q and P are d e f i n e d as above, k i s a c o n s t a n t , and n > 1. The other isotherms a l s o d i f f e r i n one or more of the above assumptions. Ad s o r p t i o n isotherms can, then, be u s e f u l i n d e s c r i b i n g the type of energy d i s t r i b u t i o n f o r the a d s o r p t i o n s i t e s . More important, they can be used to determine e n t h a l p i e s and e n t r o -p i e s of a d s o r p t i o n . ^ These, i n t u r n , have been used to e l u c i -date the nature of adsorbed i n t e r m e d i a t e s on a c a t a l y s t s u r f a c e . The best example of t h i s i s the work of Stone. ^ ® Using accurate values f o r heats of a d s o r p t i o n , he proved the e x i s t e n c e of a CO^ complex on an o x i d a t i o n c a t a l y s t used fo r the o x i d a t i o n of c a r -bon monoxide to carbon d i o x i d e . In recent years a great d e a l of a t t e n t i o n has been given to the d i r e c t study of s u r f a c e s and molecules adsorbed on s u r f a c e s . These d i r e c t s t u d i e s have been made p o s s i b l e l a r g e l y because of the development of h i g h l y r e f i n e d s p e c t r o s c o p i c techniques. I t i s beyond the scope of t h i s work to even begin d e s c r i b i n g the methods themselves. Somorjai^"^ and W e d l e r b o t h provide ex-c e l l e n t reviews of the types, t h e o r e t i c a l b a s i s , and u t i l i t y of these techniques. The importance of t h i s d i r e c t approach to s u r f a c e s t u d i e s should be c l e a r . Although there are always s e v e r a l steps i n -volved i n a c a t a l y t i c r e a c t i o n , i t i s u l t i m a t e l y the s u r f a c e 9 phenomena which are of paramount importance. Understanding how the s t r u c t u r e and p r o p e r t i e s of the surface e f f e c t the course of a chemical r e a c t i o n and conversely, how adsorbed molecules e f f e c t the s t r u c t u r e and p r o p e r t i e s of a c a t a l y s t s u r f a c e , w i l l c e r t a i n l y lead to the development of more u s e f u l c a t a l y s t s . Despite the f a c t that there are a wide v a r i e t y of methods for studying the mechanism of heterogeneous c a t a l y s i s , each approach has c e r t a i n problems associated with i t . The very rigorous spectroscopic techniques require m e t i c u l o u s l y clean surfaces and oftentimes u l t r a - h i g h vacuum. Useful c a t a l y s t s are seldom used under these c o n d i t i o n s and so there may be a problem i n e x t r a p o l a t i n g the spectroscopic r e s u l t s to a p r a c t i -c a l s i t u a t i o n . K i n e t i c s t u d i e s have t r a d i t i o n a l l y been hampered by prob-lems of r e p r o d u c i b i l i t y . K i n e t i c r e s u l t s may a l s o be unknow-i n g l y modified by the i n t e r v e n t i o n of r a t e - l i m i t i n g mass and 102 heat t r a n s p o r t processes. Even when a good k i n e t i c a n a l y s i s i s p o s s i b l e , the i n t e r p r e t a t i o n of the r e s u l t s may not be s t r a i g h t f o r w a r d . In the example c i t e d above (page 4 ) , the c o n d i t i o n s were s p e c i f i e d so that a c l e a r d i s t i n c t i o n could be made between the Langmuir-Hinshelwood and R i d e a l - E l e y mechan-isms. In f a c t , r e a c t i o n s may f o l l o w pathways i n which the con-d i t i o n s l i e somewhere between the two extremes. In that case the r e s u l t s of k i n e t i c a n a l y s i s are not so easy to interpret."*"^ In the case of adsorption isotherms, any one type of i s o -therm may not describe the adsorption process throughout the 10 whole range o f p r e s s u r e s or c o n c e n t r a t i o n s . ' u I t may not be c l e a r , t h e r e f o r e , e x a c t l y what s o r t o f s i t e d i s t r i b u t i o n i s under c o n s i d e r a t i o n . Even i f a s i n g l e d i s t r i b u t i o n d i d o c c u r , i t has been p o i n t e d out t h a t a d s o r p t i o n s i t e s do not n e c e s s a r -. . 70 l l y a l l have c a t a l y t i c a c t i v i t y . P r o d u c t a n a l y s i s s t u d i e s may be hampered by the e x i s t e n c e of heat t r a n s p o r t p r o c e s s e s which a l t e r the s e l e c t i v i t y o f the c a t a l y s t . A l s o , m u l t i p l e s u r f a c e s i t e s might e x i s t , each w i t h a d i f f e r e n t c a t a l y t i c a c t i v i t y towards a s i n g l e s u b s t r a t e . F a i l u r e t o r e c o g n i z e t h i s l a t t e r p o s s i b i l i t y can l e a d t o e r -roneous c o n c l u s i o n s based on the assumption o f a s i n g l e type of a c t i v e s u r f a c e s i t e . Because o f these v a r i o u s problems, the b e s t u n d e r s t a n d i n g o f heterogeneous c a t a l y s i s comes when the problems are approached from as many p o i n t s o f view as p o s s i b l e . The p o i n t o f view throughout t h i s t h e s i s has been t h a t of a p r a c t i c a l o r g a n i c c h e m i s t : What c o u l d be d i s c o v e r e d about p r a c t i c a l or p o t e n -t i a l l y p r a c t i c a l s y n t h e t i c c a t a l y s t s under c o n d i t i o n s used i n the l a b o r a t o r y ? A l t h o u g h t h i s approach i s not new, t h e r e i s r e l a t i v e l y l i t t l e work t h a t has been done (other than l a r g e l y e m p i r i c a l p r o d u c t a n a l y s i s s t u d i e s ) on the heterogeneous c a t a -l y s i s of t y p i c a l s o l u t i o n phase o r g a n i c r e a c t i o n s . T h i s may be c o n t r a s t e d w i t h the tremendous body o f l i t e r a t u r e which has been amassed c o n c e r n i n g the heterogeneous c a t a l y s i s o f gas phase r e a c t i o n s . 11 A l l investigations throughout th i s thesis began by deter-mining i f and how a heterogeneous catalyst would catalyze the racemization of 1,1'-binaphthyl. ( R ) - H - I J ' - b i n a p h t h y l ( S ) - ( + ) - l , r - b i n a p h t h y l Because of hindered rotation about the 1-1' bond, l,l'-binaph-thyl exists in two enantiomeric forms. The racemization reac-tion consists in the conversion of a solution with an excess of one enantiomer into an equimolar mixture of both enantiomers. Ostensibly, t h i s i s one of the simplest of a l l organic reactions. Because of th i s s i m p l i c i t y , 1,1'-binaphthyl was chosen as the substrate for investigating the possible c a t a l y t i c a c t i v i t y of a variety of heterogeneous c a t a l y s t s . These catalysts are car-bon, chemically modified carbon, Raney Nickel, and platinum (Adams' c a t a l y s t ) . A l l have been previously used almost ex-c l u s i v e l y as catalyst supports or as catalysts for hydrogena-tion reactions. The uncatalyzed conversion of enantiomers of l,l'-binaph-113 thyl has been studied by Cooke and H a ms, and more recently 114 by Carter and L i l j e f o r s . As pointed out above, hindered rotation about the 1-1' bond prevents the two naphthalene units 12 from achieving coplanarity. Cooke and Harris consider that, in addition, interference of groups in the 1 and 8 positions in each naphthalene moiety prevents coplanarity from being achieved in either one of the two ring systems. Consequently, each naph-thalene unit e x i s t s in one of two forms, termed d or 1. (d) U> d and 1 forms of substituted naphthalenes Either binaphthyl enantiomer may then e x i s t in either a racemoid, 1-1 or d-d, or a mesoid, d-1, form. In t o t a l there are six d i f f e r e n t conformational configurations for binaphthyl: R (d-d), R (d-1), R (1-1), S (d-d), S (d-1), and S (1-1). Because of rapid d * 1 conversion at ambient temperatures, the conformation of the ground state molecule i s best described as simply R or S. Nevertheless, i t i s believed that in the t r a n s i t i o n state leading to conversion of R to S, there i s a considerable difference between a conversion involving, say, R (d-1) * S (d-1) and R (1-1) * S ( 1 - 1 ) . 1 1 3 ' 1 1 4 In the l a t t e r case there are two simultaneous hydrogen-hydrogen contact points between the two ring systems in the t r a n s i t i o n state. In the former case there i s no point along the conversion path where two hydrogens interact simultaneously with two other hydrogens. 13 Rather, there are two successive hydrogen-hydrogen interactions as the enantiomers convert. The pathway involving successive interactions i s energ e t i c a l l y much more favorable than the 114 simultaneous route. Cooke and Harris thus conclude that i t i s through the mesoid forms that R and S 1,1'-binaphthyl convert. Racemoid Racemoid and mesoid conformations of S- ( + )-1,1'-binaphthyl 113 The activation energy for the reaction i s 22.5 kcal/mole.' Since the i n i t i a t i o n of t h i s work i t has been found that rate enhancements for the racemization of 1,1'-binaphthyl can be achieved by a number of methods. " These include low and h i g h energy i r r a d i a t i o n V ^ 6 t h e formation of r a d i c a l a n i o n s , ^ and the use of homogeneous cataly s t s to form the r a d i c a l ca-t i o n . The precise reason for these rate enhancements are not at t h i s time well understood. In the case of the r a d i c a l anion of 1,1'^--binaphthyl, i t appears that the conformation of 3 6 the r a d i c a l anion i s coplanar, thus destroying the c h i r a l i t y of the molecule. F i n a l l y , the discovery in t h i s laboratory**' that carbon surfaces catalyze the racemization of 1,1'-binaphthyl i s the 14 f i r s t r e p o r t o f the s u r f a c e c a t a l y s i s o f t h a t r e a c t i o n . The f o l l o w i n g c h a p t e r r e p o r t s the r e s u l t s o f subsequent s t u d i e s on the carbon c a t a l y z e d r e a c t i o n and C h a p t e r s I I I and IV d e a l w i t h the n i c k e l and p l a t i n u m c a t a l y z e d r a c e m i z a t i o n o f 1,1'-b i n a p h t h y l . I I . THE CARBON CATALYZED RACEMIZATION OF 1,1 1-BINAPHTHYL A. INTRODUCTION The l i t e r a t u r e d e a l i n g w i t h the c h e m i s t r y and t e c h n o l o g y of e l e m e n t a l carbon i s v e r y e x t e n s i v e . T e c h n i c a l a p p l i c a t i o n s i n -c l u d e a v a r i e t y o f forms of carbon - diamond, g r a p h i t e , carbon b l a c k , and c h a r c o a l - and extend over a v a r i e t y o f a r e a s such as c a t a l y s i s , a d s o r p t i o n , s u p p o r t s , m a t e r i a l s , l u b r i c a n t s , and many others."'" The use o f carbon as a c a t a l y s t i n i t s own r i g h t has been l a r g e l y r e s t r i c t e d t o carbon b l a c k s . G r a p h i t e has been made i n t o a u s e f u l c a t a l y s t by i n s e r t i n g a number o f r e a g e n t s between i t s l a y e r s (see below) t o impart d e s i r a b l e p r o p e r t i e s t o the s u r f a c e . The a s s o c i a t i o n o f c h a r c o a l s w i t h c a t a l y s i s has been l a r g e l y i n the c a p a c i t y o f h i g h s u r f a c e a r e a : s u p p o r t s upon which more e x p e n s i v e r e a g e n t s such as p l a t i n u m or p a l l a d i u m may be d e p o s i t e d w i t h a minimum inve s t m e n t of m a t e r i a l . Diamond has found few, i f any, a p p l i c a t i o n s w i t h r e g a r d t o c a t a l y s i s and w i l l not be i n c l u d e d i n t h i s d i s c u s s i o n . The types o f r e a c t i o n s which are a c t u a l l y c a t a l y z e d range over a v a r i e t y o f both i n o r g a n i c and o r g a n i c r e a c t i o n s under v a r i o u s c o n d i t i o n s . These i n c l u d e hydrogen-deuterium exchange, h y d r o g e n o l y s i s , o x i d a t i o n - r e d u c t i o n s , h a l o g e n a t i o n s , p o l y m e r i z a -2 t i o n s , i s o m e r i z a t i o n s and d e h y d r o g e n a t i o n s . I t i s c l e a r t h a t not j u s t one type o f i n t e r a c t i o n i s p o s s i b l e when a m o l e c u l e i s adsorbed on the s u r f a c e . For example, the c h e m i s o r p t i o n o f 3 9 i o d i n e and n i t r o b e n z e n e s i s b e l i e v e d t o i n v o l v e the f o r m a t i o n 4 o f charge t r a n s f e r complexes on the s u r f a c e . I s o m e r i z a t i o n s 5 and p o l y m e r i z a t i o n s , on the o t h e r hand, are thought t o proceed 16 b y way o f p r o t o n t r a n s f e r f r o m t h e s u r f a c e t o a n a d s o r b e d s u b -s t r a t e . T h e h y d r o g e n o l y s i s r e a c t i o n s m e n t i o n e d a b o v e a r e r e m i n i s c e n t o f t h e a c t i v i t y o f t r a n s i t i o n m e t a l c a t a l y s t s . ^ T h e h y d r o l y s i s o f c o m p l e x a n i o n s i s t h o u g h t t o be a b a s e c a t a -l y z e d r e a c t i o n . ^ T h e p o t e n t i a l t o c a t a l y z e s o many t y p e s o f r e a c t i o n s i s d u e t o t h e r e l a t i v e l y c o m p l i c a t e d s t r u c t u r e o f c a r b o n s . S i n c e c a r b o n b l a c k s a n d c h a r c o a l s b o t h r e f l e c t c e r t a i n a s p e c t s o f t h e g g r a p h i t e s t r u c t u r e , t h a t s t r u c t u r e w i l l be b r i e f l y r e v i e w e d . I n g r a p h i t e , t h e c a r b o n a t o m s l i e a t t h e c o r n e r s o f r e g u l a r h e x a g o n s a n d a l l a t o m i c l a y e r s o r p l a n e s a r e p a r a l l e l t o e a c h o t h e r . I n F i g u r e 1 t h e b a s i c r e p e a t i n g s t r u c t u r e a n d some a t o m i c d i m e n s i o n s a r e s h o w n . G r a p h i t e i s u s u a l l y o b t a i n e d a s a c r y s t a l -l i n e s o l i d i n w h i c h c r y s t a l l i t e s o f t h e s e d i m e n s i o n s a n d v a r i o u s s i z e s c a n be i d e n t i f i e d i n d i v i d u a l l y o r i n c l u s t e r s . S i n c e a l l 2 t h e c a r b o n a t o m s o f g r a p h i t e a r e s p h y b r i d i z e d , t h e s u r f a c e p l a n e s - c a l l e d b a s a l p l a n e s - h a v e b e e n l i k e n e d t o e x t e n d e d p o l y a r o m a t i c s y s t e m s . T h e b a s a l p l a n e s a r e , g e n e r a l l y s p e a k i n g , q u i t e i n e r t t o c h e m i c a l r e a c t i o n when t h e r e a c t i o n w o u l d c a u s e a c h a n g e i n t h e s u r f a c e s t r u c t u r e . T h e a t o m s o n t h e e d g e s o f t h e p l a n e s w i l l , h o w e v e r , h a v e u n f i l l e d v a l a n c i e s a n d s o w h e n e v e r a b a s a l p l a n e t e r m i n a t e s i n a n e d g e , k i n k , s t e p , o r some o t h e r t y p e o f d i s l o c a t i o n , q u i t e r e a c t i v e c e n t e r s w i l l be p r e s e n t . M o s t o f t h e s e s i t e s r e a c t w i t h o x y g e n t o f o r m o x i d e s , t h e m o s t common f o r m o f w h i c h i s a c a r b o x y l i c a c i d g r o u p . N e v e r t h e l e s s , b e c a u s e o f t h e e x t e n s i v e n a t u r e o f t h e b a s a l p l a n e s , g r a p h i t e s 17 F i g u r e 1. The S t r u c t u r e o f G r a p h i t e (from r e f e r e n c e 8 ) . showing three para l l e l sheets of hexagonal g r o u p i n g s of c a r b o n atoms F i g u r e 2. The S t r u c t u r e o f Carbon B l a c k s (from r e f e r e n c e 8 ) . 18 g e n e r a l l y have low s u r f a c e a r e a s (< 6 mz/g) and a low r a t i o o f edge atoms t o s u r f a c e atoms. T h e r e f o r e o n l y a v e r y s m a l l f r a c -t i o n o f the s u r f a c e i s c o v e r e d w i t h o x i d e s . The s t r u c t u r e o f carbon b l a c k s i s not n e a r l y so s t r a i g h t -f o r w a r d . There appear t o be two d i v e r g e n t s c h o o l s concerned w i t h the b a s i c s t r u c t u r e . The f i r s t and o l d e s t s c h o o l , exem-p l i f i e d by M a n t e l l , c o n s i d e r carbon b l a c k p a r t i c l e s t o be formed of r e g u l a r g r a p h i t e - l i k e c r y s t a l l i t e s which have f a i r l y r e g u l a r p a r a l l e l hexagonal u n i t s t h a t are s e p a r a t e d from each o t h e r by a r e a s o f d i s o r d e r e d (mixed v a l e n c e and randomly o r i -ented) c a r b o n . The o r i e n t a t i o n of the c r y s t a l l i t e s t o each o t h e r i s a l s o random. The second s c h o o l , as p o i n t e d out by Voet and D onnet 1^, m a i n t a i n s t h a t the g r a p h i t e - l i k e c r y s t a l l i t e s are not the b a s i c u n i t o f the carbon b l a c k , but r a t h e r the carbon b l a c k p a r t i c l e s h o u l d be c o n s i d e r e d a type o f d i s o r d e r e d polymer i n which the r e p e a t i n g u n i t i s the carbon p l a n e . Because both s c h o o l s seem t o agree on the f i n a l d e s c r i p t i o n o f the s u r f a c e , our b r i e f r e v i e w w i l l , use the model of the o l d e r s c h o o l . F i g u r e 2 b r i n g s out some of the i m p o r t a n t f e a t u r e s o f t h i s model. The s u r f a c e o f a carbon b l a c k p a r t i c l e has a l a r g e number o f edge atoms i n a d d i t i o n t o b a s a l p l a n e s analogous t o those i n g r a p h i t e . Because of the l a r g e number of edge atoms on the s u r f a c e , a major p a r t o f the s u r f a c e i s c o v e r e d w i t h o x i d e s . Oxygen may, i n f a c t , comprise as much as 11% o f the t o t a l w eight o f a carbon b l a c k and cover 50% o f the surface."'""'" 19 The b a s a l p l a n e s , o x i d e s , and pore s t r u c t u r e o f a carbon b l a c k a r i s e from the method o f p r e p a r a t i o n of the b l a c k . The g e n e r a l procedure i n v o l v e s the i n c o m p l e t e o x i d a t i o n o f some o r -g a n i c f e e d s t o c k , ' f o l l o w e d by o x i d a t i o n - t y p i c a l l y w i t h oxygen, carbon d i o x i d e or water - a t e l e v a t e d t e m p e r a t u r e . The mechanism by which the i n i t i a l f e e d s t o c k a r r a n g e s i n t o g r a p h i t e - l i k e c r y s -t a l l i t e s i s not known. However, the f i n a l m a t e r i a l w i l l c on-s i s t o f an aggregate o f carbon p a r t i c l e s . In each p a r t i c l e the atoms are arranged i n g r a p h i t e - l i k e p l a n e s s e v e r a l l a y e r s t h i c k . There i s no o r d e r i n g among the d i f f e r e n t s e t s o f g r a p h i t e - l i k e p l a n e s , a l t h o u g h i n an aggregate the p a r t i c l e s are c o n t i n u o u s 12 w i t h one a n o t h e r , presumably by way o f c h a i n s of mixed v a l e n c e 2 3 carbon (sp , sp ). S i n c e the f e e d s t o c k s may c o n t a i n q u a n t i t i e s of non-carbon c o n s t i t u e n t s , such as s u l f u r , these too w i l l be found somewhere i n the b l a c k . The p r e c i s e l o c a t i o n i s seldom known. The pore s t r u c t u r e i s thought t o d e v e l o p by h i g h tempera-t u r e o x i d a t i o n of the i n t e r n a l b a s a l planes" 1" 0 and o f the random, mixed v a l e n c e c a r b o n . The v e r y s m a l l pores which d e v e l o p from o t h i s type of o x i d a t i o n c o a l e s c e t o form m i c r o p o r e s (< 20 A) which seldom r e a c h the s u r f a c e o f the f i n a l m a t e r i a l . R a t h e r , m i c r o p o r e s run t o g e t h e r u n t i l the f i n a l pores which emerge on 0 13 the o u t e r s u r f a c e have d i a m e t e r s > 500 - 1000 A. The f i n a l carbon b l a c k w i l l v a r y w i t h r e g a r d t o p a r t i c l e and aggregate s i z e , s u r f a c e a r e a , s i z e and e x t e n t o f pore s t r u c -t u r e , and p e r c e n t o f s u r f a c e o x i d e a c c o r d i n g t o the f e e d s t o c k 20 and e x a c t n a t u r e o f p r e p a r a t i o n . There are s e v e r a l e x c e l l e n t i- s.u 8,90,10,12,13 „ . . . . . -1 r e v i e w s o f these p r o c e s s e s . V a r i a t i o n s i n a c t u a l s u r f a c e s t r u c t u r e appear t o be a matter of degree and not t y p e , so t h a t a g e n e r a l i z e d d e s c r i p t i o n o f carbon b l a c k s u r f a c e s i s appropr i a t e . The s u r f a c e s may be d i v i d e d i n t o two p a r t s : the o r g a n i z e d p a r t s and the d i s o r g a n i z e d p a r t s . The o r g a n i z e d p a r t s c o n s i s t ; o f b a s a l p l a n e s from the g r a p h i t e - l i k e c r y s t a l l i t e s . The d i s -o r g a n i z e d p a r t s c o n s i s t o f the edge atoms of b a s a l p l a n e s which emerge on the s u r f a c e and o f the randomly o r i e n t e d carbon r e -f e r r e d t o above. D u r i n g the h i g h temperature o x i d a t i o n o f a b l a c k , the b a s a l p l a n e s themselves remain i n t a c t w h i l e the o x i d a n t a t t a c k s the d i s o r g a n i z e d a r e a s . The o x i d e s found i n a carbon b l a c k are thus u s u a l l y a s s o c i a t e d w i t h the d i s o r g a n i z e d p a r t s o f the s u r f a c e . U n l i k e g r a p h i t e , i n which the p r i m a r y oxygen f u n c t i o n a l i t y i s a c a r b o x y l i c a c i d , carbon b l a c k s con-t a i n a whole spectrum o f oxygen f u n c t i o n a l i t i e s . These are l i s t e d i n Table I . I t i s the s u r f a c e o x i d e s which g i v e carbon b l a c k s t h e i r a c i d and base p r o p e r t i e s . I t has been e s t i m a t e d t h a t o n l y ~ 2% o f the s u r f a c e c o n t a i n s b a s i c o x i d e s whereas the 13 a c i d i c o x i d e s may cover as much as 20% o f the s u r f a c e . In a d d i t i o n t o the o x i d e s , double bonds are found i n the 3 d i s o r g a n i z e d a r e a s . A l s o , s a t u r a t e d carbon (sp ) i s found. As mentioned e a r l i e r , the p r e c i s e l o c a t i o n o f i m p u r i t i e s i n t r o -duced d u r i n g manufacture i s not known. Table I Oxides on Carbon C a r b o x y l i c a c i d s - C O O H H y d r o x y l f u n c t i o n s - O H Quinones L a c t o n e s 0 Chromene O x aFrom Donnett, r e f e r e n c e 25. 22 Carbon b l a c k s a re known t o g i v e a w e l l - d e f i n e d e l e c t r o n 14 s p i n resonance (ESR) spectrum. T h i s i s thought t o be due t o u n p a i r e d e l e c t r o n s p r e s e n t i n t h e ' g r a p h i t i c l a y e r s . Armstrong e t - a l " ^ showed t h a t the ESR s i g n a l c o u l d be broadened and reduced by the p h y s i c a l a d s o r p t i o n o f oxygen. S i n c e the o r i g i n a l s i g n a l c o u l d be r e c o v e r e d by d e s o r b i n g the oxygen, he c o n c l u d e d t h a t the oxygen was promoting s p i n r e l a x a t i o n and the u n p a i r e d e l e c -t r o n s , t h e r e f o r e , must be on the s u r f a c e . U n l i k e g r a p h i t e , carbon b l a c k s w i l l undergo a whole h o s t of s u r f a c e r e a c t i o n s ( i n a d d i t i o n t o the o x i d a t i o n r e a c t i o n s d u r i n g m a n u f a c t u r e ) . These i n c l u d e r e a c t i o n s c h a r a c t e r i s t i c o f a r o m a t i c m o l e c u l e s - such as s u b s t i t u t i o n s and a d d i t i o n s - and r e a c t i o n s 12 o f the s u r f a c e o x i d e s . R e a c t i o n s which are p e r t i n e n t t o our s t u d i e s w i l l be mentioned a t the a p p r o p r i a t e t i m e . C h a r c o a l s are p r e p a r e d by the t h e r m a l d e c o m p o s i t i o n o f any of a l a r g e number o f m a t e r i a l s . These i n c l u d e c o a l , p r a c t i -c a l l y any v e g e t a b l e m a t t e r , wood, bones, s u g a r s , o i l p r o d u c t s , and t a r s from c h e m i c a l p r o c e s s e s . The s t r u c t u r e o f c h a r c o a l s i s not w e l l known, but i t appears they are s i m i l a r t o carbon b l a c k s . There are a l a r g e number o f o x i d e s on the s u r f a c e , t h e r e are some b a s a l p l a n e s , and p a r t i c l e d i m e n s i o n s may be s i m i l a r . There are some i m p o r t a n t d i f f e r e n c e s , though. C h a r c o a l s do not c o n t a i n g r a p h i t e - l i k e c r y s t a l l i t e s . In terms o f s u r f a c e mor-phology the c h a r c o a l s have many more a r e a s o f d i s o r d e r than do carbon b l a c k s . 23 D e s p i t e the ready a v a i l a b i l i t y o f c h a r c o a l s and carbon b l a c k s and d e s p i t e t h e i r known a b i l i t y t o c a t a l y z e a wide range o f r e a c t i o n t y p e s , t h e r e have been r e l a t i v e l y few s t u d i e s con-cerned s p e c i f i c a l l y w i t h the c a t a l y t i c p r o p e r t i e s o f c a r b o n s . 16 17 The d i s c o v e r y i n t h i s l a b o r a t o r y ' t h a t carbon b l a c k s and c h a r c o a l s c a t a l y z e the r a c e m i z a t i o n o f 1 , 1 ' - b i n a p h t h y l * p r o -v i d e d a s i m p l e b a s i s f o r e x p l o r i n g c a t a l y t i c e f f e c t s i n a wider v a r i e t y o f o r g a n i c r e a c t i o n s . A k i n e t i c scheme f o r the c a t a -l y z e d r a c e m i z a t i o n had a l r e a d y been proposed and i n v o l v e d a s i m p l e a d s o r p t i o n - d e s o r p t i o n e q u i l i b r i u m on the carbon surface' 1" (Scheme 1 ) . T h i s mechanism r e q u i r e s the adsorbed b i n a p h t h y l t o be i n a n o n - c h i r a l c o n f o r m a t i o n . Scheme 1 1 , 1 ' - B i n a p h t h y l w i l l be r e f e r r e d t o s i m p l y as b i n a p h t h y l . 24 T h i s work was begun w i t h the i n t e n t i o n o f e s t a b l i s h i n g how g e n e r a l the r e a c t i o n was (Did i t ex t e n d t o s u b s t i t u t e d b i n a p h -t h y l s ? ) and what the e f f e c t o f s u b s t i t u e n t s would be on the c a t a l y t i c r a t e . T h i s would h e l p c h a r a c t e r i z e the p o l a r i t y o f the b i n a p h t h y l m o l e c u l e bound t o the s u r f a c e as w e l l as g i v e i n f o r m a t i o n on the n a t u r e o f the a c t i v e s i t e on c a r b o n . (Does the r e a c t i o n o c c u r on b a s a l p l a n e s or does i t i n v o l v e edge groups on carbon?) A l s o , i t was i n t e n d e d t o d e t e r m i n e the e f -f e c t o f c a t a l y s t m o d i f i c a t i o n on the c a t a l y t i c a c t i v i t y and t o t h e r e b y h e l p e s t a b l i s h the l o c a t i o n and type o f i n t e r a c t i o n i n -v o l v e d i n the c a t a l y s i s . I n i t i a l work i n v o l v e d k i n e t i c s t u d i e s on the o p t i c a l l y a c t i v e b i n a p h t h y l d e r i v a t i v e s IA-E and was i n -tended t o p r o v i d e i n f o r m a t i o n on the e f f e c t of s t r u c t u r e and e l e c t r o n i c v a r i a t i o n o f the s u b s t r a t e on the a c t i v i t y o f the c a r b o n . X A b b r e v i a t i o n IA H B i n a p h t h y l B CH-, DMB C Br DBB D N 0 2 DNB E NH^ N a p h t h i d i n e B. SYNTHESIS -OF 4,4'-DISUBSTITUTED-1,1 1-BINAPHTHYLS The s y n t h e s i s o f o p t i c a l l y a c t i v e s u b s t i t u t e d b i n a p h t h y l s r e q u i r e d e i t h e r t h a t the racemic compound be p r e p a r e d and sub-s e q u e n t l y r e s o l v e d o r t h a t o p t i c a l l y a c t i v e compounds be 25 prepared d i r e c t l y from o p t i c a l l y a c t i v e s t a r t i n g m a t e r i a l . The former method was used i n the case of b i n a p h t h y l and 4,4'-di-amino-1,1 1-binaphthyl (naphthidine) because of the ready a v a i l -20 21 a b i l i t y of methods of r e s o l u t i o n f o r these compounds ' (see Experimental s e c t i o n ) . 4 , 4 1 - D i m e t h y l - 1 , 1 1 - b i n a p h t h y l (DMB) was a l s o prepared as a racemic compound and r e s o l v e d by the f o l l o w -ing method. T h i s method u t i l i z e s the r a r e l y observed t r a n s f e r of c h i r a l i t y from a c r y s t a l of one compound to a d i f f e r e n t com-pound by the method of induced c r y s t a l growth. Approximately 30 mg of DMB and one c r y s t a l of o p t i c a l l y ac-t i v e n aphthidine were mixed i n an ampule and immersed i n a 150° o i l bath to melt the DMB but not the n a p h t h i d i n e . The ampule was then t r a n s f e r r e d to a 100° bath and the DMB allowed to c r y s t a l l i z e f o r times ranging from two hours to s e v e r a l days. The naphthidine seeds were removed by d i s s o l v i n g the c r y s t a l s i n c h loroform and washing the s o l u t i o n down a 3 cm x lh cm alumina column. S p e c i f i c r o t a t i o n s f o r i n d i v i d u a l samples of re s o l v e d DMB ranged up to + or - 95. In t h i s r e s o l u t i o n , c r y s t a l s o f DMB p r e f e r e n t i a l l y grow from the melt on the o p t i c a l l y a c t i v e naphthidine seed. T h i s type of c r y s t a l growth i s s t e r e o s e l e c t i v e because the r e l a -t i o n s h i p between the growth of one enantiomer of DMB, say R, on the naphthidine c r y s t a l , say R', i s d i a s t e r e o m e r i c with the growth of the other enantiomer on the seed. That i s , R - R' i s d i a s t e r e o m e r i c with S - R'. The two enantiomers w i l l t h e r e f o r e 26 have d i f f e r e n t r a t e s o f growth on the n a p h t h i d i n e seed.* Because the growth o c c u r s a t 100 °C, the DMB m o l e c u l e s have s u f f i c i e n t energy t o i n t e r c o n v e r t . In t h i s way the c r y s t a l l i z a t i o n p r o c e s s can, i n p r i n c i p l e , c o m p l e t e l y c o n v e r t the mel t i n t o one enan-t i o m e r . The reason a range o f s p e c i f i c r o t a t i o n s i s o b t a i n e d f o r d i f f e r e n t r e s o l u t i o n s i s t h a t o t h e r c r y s t a l l i z a t i o n p r o -c e s s e s which are not s t e r e o s e l e c t i v e , such as n u c l e a t i o n and c r y s t a l l i z a t i o n on d u s t , e t c . , are a l s o o c c u r r i n g t o v a r i o u s d e g r e e s . O p t i c a l l y a c t i v e 4 , 4 ' - d i b r o m o - 1 , 1 ' - b i n a p h t h y l (DBB) and 4 , 4 1 - d i n i t r o - 1 , 1 1 - b i n a p h t h y l (DNB) were s y n t h e s i z e d d i r e c t l y from o p t i c a l l y a c t i v e b i n a p h t h y l . The b r o m i n a t i o n r e a c t i o n was s t r a i g h t f o r w a r d , p r o c e e d i n g t o c o m p l e t i o n w i t h bromine i n c h l o r -oform a t 0 °C. Under these c o n d i t i o n s l i t t l e or no r a c e m i z a -t i o n o f b i n a p h t h y l o c c u r s . P u r i f i c a t i o n was a c h i e v e d by t r e a t -ment w i t h d e c o l o r i z i n g c h a r c o a l and washing down a 1" by %" alumina column. The n i t r a t i o n r e a c t i o n was more d i f f i c u l t . I t was neces-s a r y t o do a low temperature s y n t h e s i s t o a v o i d r a c e m i z i n g the o p t i c a l l y a c t i v e s t a r t i n g m a t e r i a l and/or p r o d u c t . However, s u i t a b l e low temperature n i t r a t i o n s c o u l d not be found i n the l i t e r a t u r e and so a new method had t o be found. A number o f d i f f e r e n t s o l v e n t s , t e m p e r a t u r e s , and r e a g e n t s were used i n c l u d -i n g HN0 3/H 2S0 4, HN0 3/AcOH, HN0 3 +.H 2S0 4/CC1 4, N 0 2 B F 4 i n * T h i s r e s o l u t i o n a l s o r e q u i r e s t h a t the DMB have a c r y s t a l s t r u c t u r e which i s non-racemate. 27 s u l f o l a n e and n i t r o m e t h a n e , and o t h e r s . The b e s t method was found t o be r e a c t i o n o f o p t i c a l l y a c t i v e b i n a p h t h y l w i t h a t e n -f o l d e x c e s s of HNC>3 and a 20 f o l d e x c e s s o f H 2 S 0 4 i n CC1 4 f o r 10 minutes a t 0 °C. The crude 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 m o s t l y 4 - n i t r o - l , 1 ' - b i n a p h t h y l , was then i s o l a t e d and r e a c t e d w i t h a t w o f o l d e x c e s s o f HNO^ and 60 f o l d e xcess o f H^SO^ i n a c e t i c a c i d a t room t e m p e r a t u r e . The r e a c t i o n was f o l l o w e d by t h i n l a y e r chromatography and, a f t e r times r a n g i n g from h hour t o 2 h o u r s , quenched w i t h water t o g i v e DNB. C. CARBON CATALYZED RACEMIZATION OF SUBSTITUTED BINAPHTHYLS A l l r e a c t i o n s were run u s i n g a 0.025 M s o l u t i o n o f sub-s t r a t e i n c h l o r o f o r m (but see the case f o r n a p h t h i d i n e b e l o w ) , and a c o n c e n t r a t i o n o f 1.0 (mg/m£) N o r i t SGI as c a t a l y s t . N o r i t i s an a c t i v a t e d c h a r c o a l o b t a i n e d from Matheson, Coleman, and B e l l and was used w i t h o u t any f u r t h e r t r e a t m e n t . T h i s c a t a l y s t was chosen because i t gave k i n e t i c runs o f c o n v e n i e n t d u r a t i o n f o r most o f the s u b s t r a t e s . A l l r e a c t i o n s e x c e p t the DNB r e a c -t i o n were run a t 23.8 °C. Because the DNB r e a c t i o n was so s l o w , i t was c a r r i e d o u t a t 48.9° and 35.9 °C. I t s v a l u e a t 23.8° was then determined from the A r r h e n i u s e q u a t i o n , k = Ae E a/ R T >-'-^ Both c a t a l y z e d and u n c a t a l y z e d r e a c t i o n s gave good s t r a i g h t l i n e s f o r f i r s t o r d e r k i n e t i c p l o t s through t h r e e h a l f l i v e s . A l l r a t e c o n s t a n t s ( k 0 k s ) were r e p r o d u c i b l e t o w i t h i n 8% e x c e p t the c a t a l y z e d r a t e c o n s t a n t f o r the DMB r e a c t i o n . Two v a l u e s f o r t h a t r a t e c o n s t a n t d i f f e r e d by 18%, but t h i s was not 28 i n v e s t i g a t e d f u r t h e r . Samples of f i r s t o r d e r k i n e t i c p l o t s used t o determine the k Q b s v a l u e s are shown f o r the u n c a t a l y z e d r e a c t i o n i n F i g u r e 3 and the c a t a l y z e d r e a c t i o n i n F i g u r e 4. The r e s u l t s , averages o f a t l e a s t two r u n s , are t a b u l a t e d i n Table I I . Table I I N o r i t SGI C a t a l y s i s o f V a r i o u s S u b s t r a t e s u b s t r a t e k u , k^ k ./k c a t uncat c a t ' uncat ( m i n - 1 x l 0 3 ) ( m i n " 1 x l 0 3 ) N a p h t h d 12 4.1 2.9 DMB 6 .4 0..9 3 6 .9 DBB 3.6 0.4 3 8.4 DNB 1.8° 0.22 C 8.2 B i n a p 17 1.2 14 a I n c h l o r o f o r m a t 23.8 °C. Q S u b s t r a t e ] = 0.025 M [ [ N o r i t ] =1.0 (mg/m£) b A v e r a g e s o f a t l e a s t two r u n s . A l l k v a l u e s from l e a s t squares c E s t i m a t e d by e x t r a p o l a t i n g In k vs 1/T curve d e t e r m i n e d f o r T = 48.9 and 35.9 °C ^ I n acetone The n a p h t h i d i n e r e a c t i o n had t o be c a r r i e d out i n ace-tone because of r e a c t i o n o f the amino group of n a p h t h i d i n e w i t h the c h l o r o f o r m s o l v e n t . The obnoxious odor which was 29 0 800 1600 2 4 0 0 3 2 0 0 time (min) F i g u r e 3. F i r s t Order K i n e t i c P l o t s f o r U n c a t a l y z e d R a c e m i z a t i o n o f S u b s t i t u t e d B i n a p h t h y l s i n CHC1 3 a t 23.8 °C. a E s t i m a t e d (see body o f t e x t ) k In acetone time (min) F i g u r e 4. F i r s t Order K i n e t i c P l o t s f o r N o r i t SGI C a t a l y z e d R a c e m i z a t i o n of S u b s t i t u t e d B i n a p h t h y l s i n CHC1 3 a t 23.8 C. [^substrate^] = 0 .025 M [ N o r i t S G l ] - 1.0 (mg/mJl) b E s t i m a t e d (see body o f t e x t ) In acetone e v o l v e d suggested p o s s i b l e f o r m a t i o n o f an i s o n i t r i l e as sug-22 g e s t e d below. RNH 2 + CHC1 3 •RNH^ + C l ~ + C C 1 2 RNH 2 + CC1 2 ^ RNH 2 — C C 1 2 ^ = — ^ + RNH = CC1 • RNC + HC1 At any r a t e , the c a t a l y z e d r e a c t i o n , a t l e a s t i n the b i n a p h t h y l c a s e , was not s t r o n g l y s o l v e n t dependent and so the i n c l u s i o n of n a p h t h i d i n e i n the comparison seems j u s t i f i e d . 16 17 As o b s e r v e d e a r l i e r , ' the c a t a l y s i s was v e r y s e n s i t i v e to i m p u r i t i e s . DNB pr e p a r e d t o t h i n l a y e r chromatography p u r i t y and then washed down s h o r t a lumina and s i l i c a columns gave v e r y poor f i r s t o r d e r p l o t s . To determine whether an i m p u r i t y was p r e s e n t i n such samples, a c a t a l y z e d b i n a p h t h y l run i n the p r e -sence o f an e q u i m o l a r amount o f v e r y pure racemic DNB was com-pared w i t h a s i m i l a r run u s i n g DNB pr e p a r e d as above. The r e -s u l t s are shown i n F i g u r e 5. Comparing the two c u r v e s o b t a i n e d w i t h DNB p r e s e n t , i t i s seen t h a t the DNB s y n t h e s i z e d as above g i v e s c o n s i d e r a b l y s l o w e r c a t a l y s i s . E l u t i n g ~ 2 grams o f t h i s 'impure' DNB down a 30 i n c h a lumina column removed t h i s i m p u r i t y and the DNB then gave s t r a i g h t , r e p r o d u c i b l e l i n e s through t h r e e h a l f l i v e s and brought the two l i n e s i n F i g u r e 5 to w i t h i n ex-p e r i m e n t a l e r r o r o f each o t h e r . The d a t a i n Table I I i n d i c a t e s t h a t a l l s u b s t r a t e s w i t h X l a r g e r than hydrogen show r a t e enhancements (as e v i d e n c e d by the r a t i o o f c a t a l y z e d t o u n c a t a l y z e d r a t e c o n s t a n t s ) c o n s i d e r a b l y 32 time (min) F i g u r e 5. The E f f e c t o f Impure DNB on the Nor i t SGI C a t a l y z e d R a c e m i z a t i o n o f B i n a p h t h y l i n CHCl^ a t 23.8 C. [ [ B i n a p h t h y l ] = 0.0 25 M [JDNB] = 0 .0 25 M [ [ N o r i t S G l ] = 1 . 0 (mg/mfi,) 33 l e s s than t h a t o f b i n a p h t h y l i t s e l f . T h i s i n d i c a t e s t h a t a s t e r i c e f f e c t o c c u r s and t h a t any group l a r g e r than hydrogen i n the 4,4' p o s i t i o n s h i n d e r s the r e a c t i o n . However, w i t h i n those compounds h a v i n g X l a r g e r than hydro-gen, a d e f i n i t e i n c r e a s e i n r e l a t i v e r a t e w i t h i n c r e a s i n g e l e c -t r o n e g a t i v i t y i s seen. T h i s i s shown i n F i g u r e 6 where the l o g Kobs i s p l o t t e d a g a i n s t Hammett's v a l u e s . ^ Comparing the two l i n e s i t i s c l e a r t h a t the d i f f e r e n c e between the c a t a l y z e d and u n c a t a l y z e d r e a c t i o n s i s g r e a t e r a t l a r g e r v a l u e s , i . e . a t g r e a t e r e l e c t r o n e g a t i v i t y o f X. T h i s d a t a i s c o n s i s t e n t w i t h the e a r l i e r p o s t u l a t e d mechan-ism i n which r a c e m i z a t i o n was o c c u r r i n g v i a a d s o r p t i o n on the p l a n a r b a s a l p l a n e s o f the carbon p a r t i c l e s . The s t e r i c e f f e c t o c c u r s as the b i n a p h t h y l i s adsorbed i n the c o p l a n a r conforma-t i o n . E l e c t r o n d o n a t i o n towards the s u b s t r a t e , which would be f a c i l i t a t e d by e l e c t r o n w i t h d r a w i n g s u b s t i t u e n t s , i s c o n s i s t e n t w i t h the known b a s i c i t y o f extended a r o m a t i c systems t o which 2 the carbon s u r f a c e has been l i k e n e d . As p o i n t e d o ut e a r l i e r , a number of f u n c t i o n a l i t i e s are known t o e x i s t on the s u r f a c e o f c a r b o n s . S i n c e i t c o u l d not be determined a t t h i s p o i n t whether such groups were d i r e c t l y or i n d i r e c t l y i n v o l v e d i n the c a t a l y s i s , i t remained t o be shown wh i c h , i f any, were i n v o l v e d i n the r a c e m i z a t i o n . For t h i s , m o d i f i c a t i o n o f the c a t a l y s t was c a r r i e d o u t t o determine i f changes i n c a t a l y t i c a c t i v i t y c o u l d be brought about by m o d i f y -i n g s u r f a c e f u n c t i o n a l i t i e s . -2.0 cn O a: O - 0 . 4 0 0 0.40 0.80 F i g u r e 6. Hammett c r P P l o t f o r U n c a t a l y z e d and N o r i t SGI C a t a l y z e d R a c e m i z a t i o n o f S u b s t i t u t e d B i n a p h t h y l s . . • LO 35 D. THE EFFECT OF OXIDATION AND REDUCTION ON THE CATALYTIC ACTIVITY OF CARBONS S i n c e many oxygen c o n t a i n i n g f u n c t i o n a l i t i e s have been shown or suggested t o occur on the s u r f a c e o f c a r b o n s , i t was f e l t t h a t v e r y g e n e r a l r e a c t i o n s such as o x i d a t i o n s and r e d u c -t i o n , which modify a g r e a t number of the groups a t o n c e , ^ ' 2 5 would be u s e f u l i n i m p l i c a t i n g any o f these f u n c t i o n a l i t i e s i n the c a t a l y t i c p r o c e s s . I f the g e n e r a l r e a c t i o n s d i d produce an e f f e c t on the a c t i v i t y o f the c a r b o n , then more s p e c i f i c r e a c -t i o n s might be run to determine which s p e c i f i c ones were a s s o -c i a t e d w i t h the c a t a l y t i c a c t i v i t y . When b e g i n n i n g these r e a c t i o n s , i t was d e c i d e d t o change from Nor i t SGI, a c h a r c o a l , t o Spheron 6, a carbon b l a c k . The reason f o r t h i s was t h a t l i t e r a t u r e i s more abundant f o r work done on carbon b l a c k s and indeed t h e r e i s much s p e c i f i c l i t e r a -t u r e f o r Spheron 6. I r o n i c a l l y , methods o f o x i d a t i o n f o r carbon b l a c k s d i d not produce carbon b l a c k s which c o u l d be used f o r k i n e t i c s t u d i e s . A c i d i c d e g r a d a t i o n p r o d u c t s which are n o r m a l l y produced from o x i d a t i o n (see below) appeared t o be washed c l e a r i n aqueous s o l u t i o n , but these same p r o d u c t s would d i s c o l o r the acetone r e a c t i o n s o l u t i o n t o the e x t e n t t h a t p o l a r i m e t e r r e a d -i n g s were i m p o s s i b l e . Acetone e x t r a c t i o n on a S o x h l e t d i d not e l i m i n a t e t h i s problem. These same methods when a p p l i e d t o the N o r i t SGI worked q u i t e w e l l . Because o f t h i s the o x i d a t i o n . r e -f e r r e d t o below was done on N o r i t and a l l o t h e r r e a c t i o n s were performed on the same bat c h o f Spheron 6. 36 Donnet and coworkers have shown t h a t the o x i d a t i o n o f c a r -24 bon b l a c k s proceeds i n t h r e e s t a g e s . In the f i r s t stage new o x i d e f u n c t i o n a l i t i e s are c r e a t e d on the s u r f a c e and the l e s s o r g a n i z e d a r e a s r e a c t t o form d e g r a d a t i o n p r o d u c t s , m a i n l y com-p l e x p o l y p h e n o l s w i t h a l i p h a t i c s i d e c h a i n s o f t e n t e r m i n a t i n g i n c a r b o x y l i c a c i d s . In the second stage the l e s s o r g a n i z e d a r e a s r e m a i n i n g on the carbon are o x i d i z e d t o carbon d i o x i d e . F i n a l l y , the o r g a n i z e d a r e a s are s l o w l y o x i d i z e d . O t h e r s have a l s o p o i n t e d out t h a t much of the o x i d a t i o n which o c c u r s does 12 so a t the expense of s u r f a c e hydrogen. The method of o x i d a t i o n o f N o r i t SGI - r e f l u x i n g i n 71% HNO^ f o r f o u r hours - i s known t o g r e a t l y i n c r e a s e the concen-t r a t i o n o f c a r b o x y l i c , p h e n o l i c , l a c t o n e , and c a r b o n y l groups on a c t i v a t e d c a r b o n s . The q u e s t i o n a r i s e s as t o whether the c h a r c o a l s u r f a c e shows analogous be h a v i o u r t o the carbon b l a c k s . A l t h o u g h p a r t i c l e s i z e , pore d e n s i t y , s p e c i f i c s u r f a c e a r e a , and o t h e r p h y s i c a l parameters may v a r y among the v a r i o u s forms of c a r b o n , the d i f f e r e n c e s between the s u r f a c e s are a m a t t e r o f degree. I t i s t h e r e f o r e r e a s o n a b l e t o e xpect c e r t a i n a n a l o g i e s i n t h e i r b e h a v i o u r towards o x i d a n t s . A l i t h i u m aluminum h y d r i d e (LAH) r e d u c t i o n o f Spheron 6 was a l s o performed. LAH r e d u c t i o n s have been used t o q u a n t i -t a t i v e l y i d e n t i f y a c i d s , l a c t o n e s , q u i n o n e s , p h e n o l s , and c a r -25 b o n y l s . The r e d u c t i o n a p p a r e n t l y does not e f f e c t the carbon e x c e p t t o reduce the o x i d e s . 37 Table I I I E f f e c t of Oxidation and Reduction on the C a t a l y t i c A c t i v i t y of Carbon C a t a l y s t s C a t a l y s t and M o d i f i c a t i o n 2 -1 (x 10 nun ) Spheron 6 LAH reduced 2.9 Blank 2.8 N o r i t SGI 71% HN0o o x i d i z e d 7.3 Blank 7.5 a I n acetone at 45.0 °C. [[Binaphthyl^] = 0.015M QSpheron 6[] = 2.5 (mg/mS,) [[Norit]] = 1.0 (mg/m£) Table I I I shows the e f f e c t of reduction and o x i d a t i o n on the a c t i v i t y of the carbons. The 'blanks' r e f e r to carbons treated and cleaned i n an i d e n t i c a l fashion to the reduction or o x i d a t i o n , but without a c t u a l l y i n t r o d u c i n g the reducing or o x i d i z i n g agent (see Experimental s e c t i o n ) . The rate constants obtained for the o x i d i z e d or reduced c a t a l y s t remained essen-t i a l l y the same as those obtained for the r e s p e c t i v e blanks. A number of conclusions should be drawn from Table I I I . F i r s t of a l l , o x i d a t i o n and reduction together would have e f -fected a l l of the known oxide f u n c t i o n a l i t i e s on carbon. A l s o , the o x i d a t i o n would have o x i d i z e d surface hydrogen. P r o v i d i n g the oxides and hydrogen were a l l a c c e s s i b l e to the reagents used (and to b i n a p h t h y l ) , they do not appear to be involved i n 38 the c a t a l y s i s . S e c o n d l y , s i n c e the o x i d e s and hydrogen are a s s o c i a t e d w i t h the d i s o r g a n i z e d a r e a s on the s u r f a c e , and s i n c e the o x i d a t i o n r e a c t i o n i s known t o occur i n the same a r e a s , the a c t u a l c a t a l y t i c s i t e s would appear t o be a s s o c i -ated w i t h the o r g a n i z e d a r e a s , i . e . the b a s a l p l a n e s . To c o r r o b o r a t e these f i n d i n g s i t was d e c i d e d t o see what e f f e c t r e a c t i o n s such as c h l o r i n a t i o n and b r o m i n a t i o n , which are thought t o occur a t the b a s a l p l a n e s , would have on the c a t a l y t i c a c t i v i t y o f Spheron 6. E. THE EFFECT OF CHLORINATION AND BROMINATION ON THE ACTIVITY OF CARBONS T h e c h l o r i n a t i o n and b r o m i n a t i o n o f carbon b l a c k s u r f a c e s are two ty p e s o f r e a c t i o n s which may occur on the p o l y a r o m a t i c b a s a l p l a n e s . P u r i and B a n s a l have used the a d s o r p t i o n o f 2 f5 aqueous bromine as a measure of u n s a t u r a t i o n o f the s u r f a c e . C h l o r i n e may be adsorbed e i t h e r by s u b s t i t u t i o n f o r hydrogen or by a d d i t i o n a t areas o f u n s a t u r a t i o n . The a d d i t i o n r e a c -t i o n o c c u r s a t the same s i t e s as the bromine a d d i t i o n . R i v i n and M e d a l i a have l i k e n e d these a d d i t i o n s t o the f i r s t 12 stage o f 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 . The r e a c t i o n i n v o l v e s i n i t i a l f o r m a t i o n o f a charge t r a n s f e r complex between the m o l e c u l a r halogen and the b a s a l p l a n e s . T h i s i s f o l l o w e d by f o r m a t i o n o f a c o v a l e n t c a r b o n - h a l o g e n bond. The bond may a c t u a l l y be d i s p l a c e d by a p p r o p r i a t e i o n i c and n o n - i o n i c n u c l e o -44 p h i l e s . 39 S i n c e both the a d d i t i o n s and the c a t a l y t i c a c t i v i t y o f the carbon b l a c k towards r a c e m i z a t i o n appeared t o be a s s o c i a t e d w i t h the b a s a l p l a n e s , i t was of i n t e r e s t t o determine how ha l o g e n a -t i o n e f f e c t e d c a t a l y t i c a c t i v i t y . C h l o r i n a t i o n was done i n the 2 7 gas phase a t 450° u s i n g the method o f P u r i . e t a l . P u r i ' s 28 method was a l s o used f o r the b r o m i n a t i o n r e a c t i o n . A l l r e a c -t i o n s were done on the same b a t c h o f Spheron 6. In o r d e r t o compare the c h l o r i n a t e d and brominated c a t a l y s t s , the i n i t i a l Spheron 6 was washed and degassed a t 450 °C b e f o r e b e i n g h a l o -genated. T h i s e l i m i n a t e d any changes i n the c a t a l y s t due t o h e a t i n g d u r i n g the c h l o r i n a t i o n . I t was a n t i c i p a t e d t h a t the presence o f halogens on the s u r f a c e would l i k e l y b l o c k the s i t e s f o r b i n a p h t h y l a d s o r p t i o n and thus d ecrease the a c t i v i t y o f the c a t a l y s t . I t was t h e r e -f o r e s u r p r i s i n g t o f i n d a d r a m a t i c i n c r e a s e i n c a t a l y t i c a c t i v i t y w i t h the h a l o g e n a t e d carbon b l a c k . T h i s i s seen i n Table IV where the f i r s t o r d e r r a t e c o n s t a n t , k0|_)s, i s shown f o r the v a r i o u s c a t a l y s t s . The blank r e f e r s t o the heat t r e a t e d Spheron 6 d e s c r i b e d above. The brominated c a t a l y s t i s n e a r l y n i n e times more a c t i v e than the b l a n k . The e f f e c t o f c h l o r i n e on the c a t a l y s t was t o make the c a t a l y z e d r e a c t i o n too f a s t t o measure a t 25°. Even a t a temperature o f 0.4° the v a l u e f o r ^ Q ] - ) S w a s g r e a t e r than t w i c e t h a t o f the blank a t 25°. S i n c e R i v i n and Aron had shown t h a t the halogens c o u l d be d i s p l a c e d by a p p r o p r i a t e n u c l e o p h i l e s , the e f f e c t o f l i t h i u m 40 T a ble IV E f f e c t o f C h l o r i n a t i o n and B r o m i n a t i o n on the C a t a l y t i c A c t i v i t y o f Spheron 6 a C a t a l y s t M o d i f i c a t i o n Blank Brominated B r o m i n a t e d , LAH reduced C h l o r i n a t e d 1 3 C h l o r i n a t e d , LAH reduced a I n acetone a t 25.0 °C. [ [ B i n a p h t h y l ] = 0.015 M [[Spheron 6 ] =1.5 (mg/mJl) V 0.4 °C aluminum h y d r i d e (LAH) on the h a l o g e n a t e d c a t a l y s t s was a l s o de-te r m i n e d . In Table IV i t i s seen t h a t LAH t r e a t m e n t r e s t o r e s the c a t a l y s t t o a p p r o x i m a t e l y i t s i n i t i a l a c t i v i t y , i n d i c a t i n g the e f f e c t o f the halogen i s l o s t when the halogen i t s e l f i s removed by h y d r i d e i o n . S i n c e the d i s p l a c e m e n t o f e i t h e r c h l o r -i n e or bromine g i v e s e s s e n t i a l l y the same a c t i v i t y c a t a l y s t , i t would appear t h a t both halogens are e x e r t i n g t h e i r i n f l u e n c e on the same f r a c t i o n o f the s u r f a c e . T h i s i s c o n s i s t e n t w i t h the f a c t t h a t both add t o the carbon b l a c k s u r f a c e a t the b a s a l p l a n e s and i s a l s o c o n s i s t e n t w i t h the c a t a l y t i c a c t i v i t y b e i n g a s s o c i a t e d w i t h the b a s a l p l a n e s . k o b s ( x 1 0 3 m i n ~ > 4.3 35 3.5 9.2 3.6 41 In a d d i t i o n t o showing i n c r e a s e d c a t a l y t i c a c t i v i t y , h a l -ogenated Spheron 6 a l s o showed a s o l v e n t e f f e c t which d i d not occur w i t h the u n t r e a t e d c a t a l y s t . Table V l i s t s the v a l u e s o b t a i n e d f o r ^ 0 ^ s i n a number of s o l v e n t s u s i n g the brominated c a t a l y s t . By c o n t r a s t , the u n t r e a t e d c a t a l y s t gave a k k s 50% g r e a t e r i n c h l o r o f o r m than i n a c e t o n e , a s m a l l e r change i n the o p p o s i t e d i r e c t i o n as the brominated c a t a l y s t . Table V The E f f e c t o f S o l v e n t on k o b s f o r Brominated Spheron 6 a S o l v e n t acetone d i c h l o r o m e t h a n e e t h y l a c e t a t e c h l o r o f o r m carbon t e t r a c h l o r i d e a A t 25.0 ° C . [ B i n a p h t h y l ^ ] = 0.015 M [[Brominated Spheron 6[] =1.5 (mg/m£) There are s e v e r a l p o s s i b l e e x p l a n a t i o n s f o r the u n e x p e c t e d l y h i g h a c t i v i t y o f the h a l o g e n a t e d c a t a l y s t . I t i s p o s s i b l e t h a t adsorbed halogen i t s e l f p r o v i d e s new s i t e s f o r c a t a l y s i s . How-e v e r , the f a c t t h a t m o l e c u l a r bromine i t s e l f does not racemize k o b s ( x 1 ( ) 2 m i n 1 } 3.5 1.2 2.3 1.2 2.3 42 b i n a p h t h y l mediates a g a i n s t t h i s . * Another p o s s i b i l i t y would be t h a t f r e e r a d i c a l s were r e s p o n s i b l e f o r c a t a l y s i s and more r a d i c a l s i t e s had been g e n e r a t e d i n the presence o f the h a l o -gens. T h i s a c t i v i t y would n ot l i k e l y be removed by LAH t r e a t -ment . Yet another e x p l a n a t i o n would be t h a t the a d d i t i o n o f mol-e c u l a r halogen adds e l e c t r o n s t o the s u r f a c e by way o f the new carbon-halogen bond which i s formed. I n c r e a s e d e l e c t r o n d e n s i t y may make the s u r f a c e a b e t t e r e l e c t r o n donor. However, s i n c e c h l o r i n e i s more e l e c t r o n e g a t i v e than bromine, t h i s approach would p r e d i c t t h a t the brominated r a t h e r than the c h l o r i n a t e d c a t a l y s t would be more a c t i v e . An e x p l a n a t i o n f o r both the e f f e c t o f halogen and the r e -s u l t i n g s o l v e n t dependence may i n v o l v e c o n s i d e r a t i o n of the e f f e c t o f chemisorbed s o l v e n t on the c o u r s e o f the c a t a l y z e d r e a c t i o n . R i v i n and I l l i n g e r ^ ' 3 0 have found t h a t when a c a r -bon b l a c k adsorbs an o r g a n i c l i q u i d or v a p o r , a s i g n i f i c a n t p o r -t i o n of the a d s o r b a t e becomes so t i g h t l y bound t o the s u r f a c e t h a t i t can o n l y be removed by h e a t i n g the b l a c k t o te m p e r a t u r e s r a n g i n g from 150° t o 400 °C. The r e s i s t a n c e t o d e s o r p t i o n i s n o t , however, due t o a h i g h a c t i v a t i o n energy f o r the d e s o r p t i o n r e a c t i o n . In a k i n e t i c s tudy u s i n g acetone as the a d s o r b a t e , R i v i n and I l l i n g e r found t h a t the slow d e s o r p t i o n r a t e was due to a v e r y low f r e q u e n c y f a c t o r . ^ 9 ' 3 0 * R e c a l l t h a t the b r o m i n a t i o n o f o p t i c a l l y a c t i v e b i n a p h t h y l d i d not racemize the b i n a p h t h y l , but r a t h e r gave o p t i c a l l y a c t i v e 4 , 4 1 - d i b r o m o - 1 , 1 1 - b i n a p h t h y l . (See E x p e r i m e n t a l s e c t i o n . ) 43 The low f r e q u e n c y f a c t o r c o r r e s p o n d s t o a complete l o s s of t r a n s l a t i o n a l motion i n the d e s o r p t i o n t r a n s i t i o n s t a t e and r e -q u i r e s t h a t the adsorbed m o l e c u l e have f r e e s u r f a c e m o b i l i t y . By c o n t r a s t , the r a t e s o f d e s o r p t i o n o f l o c a l i z e d c h e m i s o r p t i o n s , 29 such as those which occur on s p e c i f i c s i t e s on s i l i c a , o c c u r w i t h h i g h e r f r e q u e n c y f a c t o r s and h i g h e r a c t i v a t i o n e n e r g i e s . In the s i l i c a case a slow d e s o r p t i o n ( s t r o n g c h e m i s o r p t i o n ) i s due t o a s t r o n g i n t e r a c t i o n between the acetone and the s i l i c a s u r f a c e and not t o h i g h acetone s u r f a c e m o b i l i t y . 12 R i v i n and M e d a l i a go on t o p o i n t out t h a t f a c t o r s which e f f e c t s u r f a c e m o b i l i t y w i l l have a d r a m a t i c e f f e c t on the s t a -b i l i t y o f the chemisorbed m o l e c u l e . In the case o f c a r b o n s , the m o b i l e a d s o r b a t e i s a s s o c i a t e d w i t h the smooth, e x t e n s i v e , b a s a l p l a n e s r a t h e r than w i t h the o x i d e s where more l o c a l i z e d bonding would be expected t o o c c u r . C h e m i s o r p t i o n r o u g h l y c o r -responds t o one m o l e c u l e per b a s a l p l a n e but i s independent o f 12 the s i z e of the p l a n e . A d s o r p t i o n o f much more than one mole-c u l e per b a s a l p l a n e a p p a r e n t l y l e a d s t o l a t e r a l i n t e r a c t i o n s 12 which g r e a t l y r e s t r i c t a d s o r b a t e m o b i l i t y . In c o n j u n c t i o n w i t h these f i n d i n g s , heat t r e a t m e n t o f a carbon l e a d s t o a c o -a l e s c i n g o f the b a s a l p l a n e s and a d e c r e a s e i n the amount chem-i s o r b e d 3 0 because the t o t a l number of p l a n e s d e c r e a s e s . L i k e -w i s e , m o d i f i c a t i o n s o f the b a s a l p l a n e s which p o r t i o n the p l a n e s i n t o s m a l l e r a d s o r b i n g u n i t s w i l l i n c r e a s e the t o t a l amount chemisorbed but w i l l a l s o i n c r e a s e the ease w i t h which the 44 a d s o r b a t e s may be removed. M o d i f i c a t i o n s which are known t o produce t h i s e f f e c t i n c l u d e the f i x i n g o f o r g a n i c p e r o x i d e s , 31 32 h y d r o p e r o x i d e s , and oxygen. ' I f we assume t h a t the c a t a l y t i c s i t e f o r b i n a p h t h y l r a c e -m i z a t i o n i s on the b a s a l p l a n e s - as a l l the e v i d e n c e i n d i c a t e s -and t h a t a s o l v e n t m o l e c u l e must be d i s p l a c e d i n o r d e r t o make the s i t e a c c e s s i b l e , then our r e s u l t s can be e x p l a i n e d u s i n g R i v i n ' s model f o r s o l v e n t c h e m i s o r p t i o n . E s s e n t i a l l y , the ex-p l a n a t i o n i n v o l v e s the d i f f e r e n c e between d i s p l a c i n g a s o l v e n t m o l e c u l e from a b a s a l p l a n e ( i n o r d e r t o make room f o r a b i n a p h -t h y l m o l e c u le) b e f o r e and a f t e r f i x i n g a halogen t o i t . Because of the g r e a t e r m o b i l i t y on the u n m o d i f i e d s u r f a c e , the r a t e con-s t a n t f o r d e s o r p t i o n o f s o l v e n t w i l l be l e s s than on the modi-f i e d s u r f a c e . I f we c o n s i d e r the s o l v e n t m o l e c u l e t o be a type o f i n h i b i -t o r , then i n the complete e x p r e s s i o n f o r the c a t a l y z e d r a t e 17 c o n s t a n t ( E q u a t i o n ) , the v a l u e o f k_j has been d e c r e a s e d , and so a l s o the o v e r a l l r a t e o f c a t a l y s i s . n i v v 2k k 2 [ ] C t o t a l ^ L -U k o b s k o b s , u n c a t + k± [ [ b i n a p h t h y l ^ + 2 k 2 + 2 k 2 k [ i ] / ^ (From r e f e r e n c e 17 and Scheme 1, p. 23) With the h a l o g e n a t e d c a t a l y s t , as w i t h carbon b l a c k s modi-31 3 2 f i e d w i t h p e r o x i d e s and oxygen, ' the c h e m i s o r p t i o n s t a b i l i t y has been d e c r e a s e d by l o w e r i n g the s u r f a c e m o b i l i t y o f the ad-sorbed s o l v e n t . T h i s would i n c r e a s e k_^ i n e q u a t i o n [|l[] and hence i n c r e a s e the o v e r a l l r a t e o f c a t a l y s i s . 45 An e x p l a n a t i o n f o r the s o l v e n t e f f e c t and f o r the l a r g e r i n c r e a s e i n a c t i v i t y with c h l o r i n a t i o n compared to bromination i s not so s t r a i g h t f o r w a r d . I t may be that on the non-halogenated s u r f a c e frequency f a c t o r s ( i . e . s u r f a c e m o b i l i t y ) are the most important f a c t o r s e f f e c t i n g d e s o r p t i o n . The f a c t t h a t o n l y s m a l l s o l v e n t e f f e c t s were observed on the non-halogenated c a t a l y s t would i n d i c a t e that frequency f a c t o r s were comparable for the d i f f e r e n t s o l v e n t s . * Conversely, with the halogenated c a t a l y s t the s t r e n g t h of the s o l v e n t - s u r f a c e i n t e r a c t i o n may dominate the d e s o r p t i o n r a t e . T h i s i n t e r a c t i o n c o u l d be e f f e c t e d by the type of s o l v e n t and the type of bound halogen. F. SOLVATED ELECTRON CATALYZED RACEMIZATION OF 1,1'-BINAPHTHYL The formation of a b i n a p h t h y l r a d i c a l anion on the s u r f a c e i s an i n t e r e s t i n g p o s s i b i l i t y to account fo r the e l e c t r o n donat-12 33 38 ing mechanism. As p o i n t e d out by other authors, ' ' the b a s a l planes can a c t as e l e c t r o n donors f o r v a r i o u s acceptor molecules. The halogenation of carbon s u r f a c e s i s b e l i e v e d to i n v o l v e i n i t i a l formation of a charge t r a n s f e r complex with the b a s a l planes as e l e c t r o n d o n o r s . 3 A s i m i l a r suggestion has been* 33 made for the a d s o r p t i o n of n i t r o p h e n o l s on the b a s a l p l a n e s . To t e s t the p l a u s i b i l i t y of such an i n t e r a c t i o n causing the r a c e m i z a t i o n of b i n a p h t h y l , i t was decided to t e s t the a c t i v i t y of a s o l u t i o n of s o l v a t e d e l e c t r o n s towards a s o l u t i o n of * The c a t a l y z e d r a t e was the same i n acetone, e t h a n o l , 2% water-ethanol, cyclohexane, and heptane. The k o b s i n chloroform was 50% l a r g e r than i n acetone. 46 o p t i c a l l y a c t i v e b i n a p h t h y l . The r e a c t i o n i n v o l v e d simply mix-ing the two s o l u t i o n s (in hexamethyl phosphoramide) and f i l l i n g a p o l a r i m e t e r c e l l with the r e s u l t i n g f a i n t y e l l o w s o l u t i o n . P o l a r i m e t e r readings c o u l d then be e a s i l y taken at short i n t e r -v a l s . F i g u r e 7 i s a p l o t of the p o l a r i m e t e r r e a d i n g , a , as a f u n c t i o n o f time. Upon adding the s o l u t i o n of s o l v a t e d e l e c t r o n s to the b i -naphthyl s o l u t i o n , there i s an immediate drop i n the o p t i c a l a c t i v i t y o f the s o l u t i o n . T h i s immediate l o s s i s followed by a f i r s t order decay i n a . Fig u r e 8 shows a number of f i r s t order k i n e t i c p l o t s f o r the r a c e m i z a t i o n . The i n i t i a l l o s s i s propor-t i o n a l to the i n i t i a l c o n c e n t r a t i o n o f e l e c t r o n s , as i s the f i r s t order r a t e process which f o l l o w s . A f t e r s e v e r a l hours the rat e of ra c e m i z a t i o n begins to slow down. The i n i t i a l l o s s i n o p t i c a l a c t i v i t y i s due to the very r a p i d r a c e m i z a t i o n of the r a d i c a l anion of b i n a p h t h y l . Subse-34 35 quent to t h i s work other authors made the same o b s e r v a t i o n . ' Molecular o r b i t a l c a l c u l a t i o n s have shown that the conformation of the r a d i c a l anion of b i n a p h t h y l i s a c t u a l l y coplanar and 3 6 t h e r e f o r e would show no o p t i c a l a c t i v i t y . C l e a r l y , the g r e a t -er the number of r a d i c a l anions formed, the l a r g e r the i n i t i a l decrease i n a . The r a d i c a l anions can exchange an e l e c t r o n with n e u t r a l b i n a p h t h y l molecules i n a r e a c t i o n which leads to r a c e m i z a t i o n but at a much slower r a t e than the i n i t i a l r a d i c a l anion f o r -mation. T h i s i s shown i n Scheme 2. 0.200-A [(+)-Binaphthyl] = 0.025 M IOO 200 300 min. 400 500 600 F i g u r e 7. a v e r s u s Time f o r the S o l v a t e d E l e c t r o n C a t a l y z e d R a c e m i z a t i o n o f B i n a p h t h y l . [JSIaJ r e f e r s t o the c o n c e n t r a t i o n o f d i s s o l v e d sodium used t o prepare the s o l u t i o n o f s o l v a t e d e l e c t r o n s . : i i i 1 1 1 1 1 mm. IOO 200 300 400 500 600 700 800 nF ! ^ U r e 8 : < . v . F 1 i r S t o ° r d e r K i n e t i c P l o t s for the S o l v a t e d E l e c t r o n C a t a l y z e d R a c e m i z a t i o n o f B m a p h t h y l . See F i g u r e 7 f o r e x p l a n a t i o n o f Q j a ] . r a c e m i z a t i o n co 49 R £ S * 2 * R + Binaphthyl] ^ • Binaphthyl] + S where R and S are the two enantiomers of b i n a p h t h y l Scheme 2 F i r s t order r a t e constants are then determined from a In (a/a ) + 2 versus time p l o t as From F i g u r e 8 i t i s seen that a higher i n i t i a l c o n c e n t r a t i o n of s o l v a t e d e l e c t r o n s g i v e s . a f a s t e r f i r s t order r e a c t i o n . T h i s i s because the higher c o n c e n t r a t i o n of r a d i c a l anions i n s o l u -t i o n w i l l , by equation [J2] , r e s u l t i n a f a s t e r exchange of e l e c t r o n s between n e u t r a l and r a d i c a l anion b i n a p h t h y l molecules. From these experiments i t appeared reasonable to expect that i f a r a d i c a l anion of b i n a p h t h y l were formed on the b a s a l planes of a carbon, i t would provide a f a c i l e means of r a c e m i z a t i o n . To determine whether r a d i c a l anion formation on the b a s a l planes would indeed lead to r a c e m i z a t i o n , i t was decided to c o n s t r u c t a model s u r f a c e which would mimic the expected a c t i v i t y of the carbons. G r a p h i t e , with i t s e x t e n s i v e b a s a l planes, would pro-vide an e x c e l l e n t model. Graphite i t s e l f i s c a t a l y t i c at high enough c o n c e n t r a t i o n s and, i n a d d i t i o n , the e l e c t r o n i c p r o p e r t i e s k . = k, + k~ p B i n a 50 of the s u r f a c e can be mo d i f i e d by i n s e r t i n g a p p r o p r i a t e reagents between the g r a p h i t i c l a y e r s . In p a r t i c u l a r , the i n s e r t i o n ( i n t e r c a l a t i o n ) of potassium i n t o g r a p h i t e c r e a t e s a c a t a l y s t which i s known to c a t a l y z e e l e c t r o n t r a n s f e r r e a c t i o n s . I t was thus decided to determine how potassium-graphite i n t e r c a l a t e s (and others) compared with g r a p h i t e i n t h e i r a c t i v i t y towards b i n a p h t h y l r a c e m i z a t i o n . G. GRAPHITE INTERCALATE CATALYZED RACEMIZATION OF 1,1'-BINAPHTHYL The process by which some r e a c t a n t d i f f u s e s between the l a y e r s of a l a m e l l a r s t r u c t u r e i s termed i n t e r c a l a t i o n . In the case of g r a p h i t e , a l a r g e number of reagents can be i n s e r t e d between the w e l l - o r d e r e d l a y e r s to impart d e s i r a b l e s u r f a c e 37 p r o p e r t i e s to the g r a p h i t e . Although the exact s t r u c t u r e of the f i n a l i n t e r c a l a t e v a r i e s with the d i f f e r e n t r e a c t a n t s which are i n s e r t e d , there are some gen e r a l f e a t u r e s which are char-a c t e r i s t i c of a l l the i n t e r c a l a t e s . I n t e r c a l a t i o n leads to an in c r e a s e i n the i n t e r l a y e r d i s -tance of the g r a p h i t e l a y e r s . The amount of the r e s u l t i n g s w e l l -ing of the g r a p h i t e depends on how many of the carbon-carbon l a y e r s are f i l l e d and the reagent which i n t e r c a l a t e s . The num-ber o f such f i l l e d l a y e r s i s d e s c r i b e d i n terms of the number of carbon l a y e r s s e p a r a t i n g the i n t e r c a l a t i n g l a y e r s . A f i r s t stage compound i s one i n which a s i n g l e carbon l a y e r separates the i n t e r c a l a t i n g l a y e r s , a second stage compound has two such 51 carbon l a y e r s , a three stage t h r e e , and so on. Separations and o r i e n t a t i o n s w i t h i n the carbon l a y e r do not change as a r e s u l t of i n t e r c a l a t i o n . The e l e c t r o n d e n s i t y of the b a s a l planes changes with the 39 type of i n t e r c a l a t i n g r e a c t a n t . For example, potassium i n t e r -c a l a t e s with the t r a n s f e r of an e l e c t r o n from the potassium to 41 the g r a p h i t e b a s a l plane. With f e r r i c c h l o r i d e , e l e c t r o n den-40 s i t y i s removed from the b a s a l p l a n e s . The i n t e r c a l a t i n g l a y e r takes on an ordered s t r u c t u r e which i s determined at l e a s t to some extent by the s t r u c t u r e of graph-39 i t e . Two arrangements which Hennig has proposed c o n s i s t of hexagonal and t r i g o n a l d i s t r i b u t i o n s of r e a c t a n t s w i t h i n a l a y -e r . These arrangements may change with the stage of the com-39 pound. A l s o , l a t e r a l displacements may occur between succes-s i v e r e a c t a n t l a y e r s . To t e s t our r a d i c a l anion mechanism for b i n a p h t h y l racemiza-t i o n on carbon s u r f a c e s , we prepared a potassium-graphite i n t e r -c a l a t e and compared i t s a c t i v i t y towards r a c e m i z a t i o n with that of g r a p h i t e i t s e l f . Our method of p r e p a r a t i o n was that .of L a l a n -4 2 c e t t e et a l and produced an i n t e r c a l a t e with s t o i c h i o m e t r y C^K/ a mixture of one stage CgK and two stage C^K. As with the other carbon c a t a l y s t s , the i n t e r c a l a t e gave good f i r s t order k i n e t i c s throughout the course of the c a t a l y z e d r a c e m i z a t i o n . F i g u r e 9 g i v e s f i r s t order p l o t s f o r the uncata-l y z e d r e a c t i o n and f o r both the g r a p h i t e and potassium-graphite i n t e r c a l a t e c a t a l y z e d r e a c t i o n s . The i n t e r c a l a t e c a t a l y z e d Time (min) 50 100 F i g u r e 9. F i r s t Order K i n e t i c P l o t for the Potassium-Graphite I n t e r c a l a t e C a t a l y z e d en Racemization of B i n a p h t h y l i n n-Heptane at 40.0 °C. ("catalyst] = 41 (mg/mfi,) g r a p h i t e 1 0 (see Experimental s e c t i o n ) [[Binaphthyl]] = 0.015 M 53 r e a c t i o n was q u i t e s e n s i t i v e to i m p u r i t i e s i n the s o l v e n t and r e a c t i o n atmosphere. Using u n d i s t i l l e d s o l v e n t s or t e c h n i c a l grade gases would d e s t r o y the a c t i v i t y of the i n t e r c a l a t e . D i s -t i l l i n g the s o l v e n t and using reagent grade argon remedied t h i s . Comparing the l i n e s f o r g r a p h i t e and the potassium-graphite i n t e r c a l a t e i n F i g u r e 9, i t i s c l e a r that potassium i n t e r c a l a -4: t i o n enhances the c a t a l y t i c a c t i v i t y of g r a p h i t e . L a l a n c e t t e et a l 4 3 and B e r g b r e i t e r and K i l l o u g h have both found that CgK i n t e r -c a l a t e s are capable of c a t a l y z i n g r e a c t i o n s by way of i n i t i a l one e l e c t r o n t r a n s f e r s . B e r g b r e i t e r and K i l l o u g h ' s work, i n p a r t i c u l a r , i s r e l e v a n t to our case because they proposed the formation of the r a d i c a l anion of naphthalene on the i n t e r c a l a t e s u r f a c e . I f such an e l e c t r o n t r a n s f e r were o c c u r r i n g i n our case, i t would account f o r the b i n a p h t h y l r a c e m i z a t i o n . Insofar as the potassium-graphite i n t e r c a l a t e i s a good model for an e l e c t r o n donating carbon s u r f a c e , the carbon c a t a -l y z e d r a c e m i z a t i o n of b i n a p h t h y l would a l s o be a r a d i c a l anion type r e a c t i o n . N e v e r t h e l e s s , i t should be noted t h a t not o n l y e l e c t r o n donating, but e l e c t r o n withdrawing s u r f a c e s as w e l l w i l l c a t a l y z e the r a c e m i z a t i o n of b i n a p h t h y l . A f e r r i c c h l o r i d e -g r a p h i t e i n t e r c a l a t e a l s o showed i n c r e a s e d c a t a l y t i c a c t i v i t y over g r a p h i t e i t s e l f (Figure 10). Since i n t e r c a l a t i n g f e r r i c 40 c h l o r i d e reduces the e l e c t r o n d e n s i t y on the g r a p h i t i c s u r f a c e , i t appears that i n c r e a s e d a c t i v i t y r e s u l t s from a g r e a t e r t e n -dency of the b i n a p h t h y l molecule to donate e l e c t r o n d e n s i t y i n t o the s u r f a c e . T h i s i s not i n c o n s i s t e n t with our other time(min) 50 100 150 F i g u r e 10. F i r s t Order K i n e t i c P l o t f o r the F e C l o - G r a p h i t e I n t e r c a l a t e C a t a l y z e d Racemization of B i n a p h t h y l i n n-Heptane at 25.0 °C. [ [ c a t a l y s t ] = 41 (mg/m£) g r a p h i t e (see Experimental s e c t i o n ) [[Binaphthyl] = 0.015 M 55 f i n d i n g s s i n c e , as R i v i n and Medalia" 1"^ and W e i s s J U have poi n t e d out, e l e c t r o n t r a n s f e r s on carbons may proceed e i t h e r to or from the s u r f a c e , depending on the nature of the d i f f e r e n t adsorbent-adsorbate system. T h i s would a l s o be c o n s i s t e n t with the f i n d -89 ing of C o l t e r and Clemens t h a t , i n charge t r a n s f e r complexes where b i n a p h t h y l a c t s as donor, b i n a p h t h y l w i l l racemize more r a p i d l y than i n the n e u t r a l s t a t e . H. CONCLUSION The r a c e m i z a t i o n of b i n a p h t h y l on carbon s u r f a c e s proceeds by a mechanism i n which e l e c t r o n d e n s i t y i s donated to the b i -naphthyl by the carbon s u r f a c e . The c a t a l y t i c r a t e i s u n a f f e c t e d by o x i d a t i o n s and r e d u c t i o n s which occur at the d i s o r g a n i z e d areas of the s u r f a c e . Conversely, halogenation r e a c t i o n s , which are b e l i e v e d to occur at the b a s a l p l a n e s , have a dramatic e f -f e c t on the c a t a l y t i c r a t e . T h i s i n d i c a t e s that the s i t e s f o r bi n a p h t h y l r a c e m i z a t i o n are l o c a t e d on the b a s a l planes and not on the d i s o r g a n i z e d areas or the edge atoms. Rate enhancements achieved by c h l o r i n a t i n g or brominating the carbon s u r f a c e are e x p l a i n e d i n terms of R i v i n ' s model f o r chem i s o r p t i o n . In t h i s model, the entropy of chemisorbed s o l -vent molecules i s i n c r e a s e d by d i s r u p t i n g the b a s a l p l a n e s . In our case, such an in c r e a s e may f a c i l i t a t e displacement of s o l -vent molecules from r a c e m i z a t i o n s i t e s by b i n a p h t h y l molecules. Racemization of b i n a p h t h y l may i n v o l v e the formation of a b i n a p h t h y l r a d i c a l anion on the s u r f a c e . T h i s i s c o n s i s t e n t 56 with the known behaviour of b i n a p h t h y l r a d i c a l anions and with the tendency of the b a s a l planes of carbon to form charge t r a n s -f e r complexes with other adsorbates. T h i s idea was t e s t e d using g r a p h i t e i n t e r c a l a t e s as models f o r the b a s a l planes of the c a r -bon s u r f a c e . I n t e r c a l a t i n g potassium i n t o g r a p h i t e enhances the c a t a l y t i c a c t i v i t y of the g r a p h i t e . Since potassium-graphite i s known to c a t a l y z e r e a c t i o n s by one e l e c t r o n t r a n s f e r , i t would appear that a r a d i c a l anion mechanism f o r c a t a l y z e d b i n a p h t h y l racemi-z a t i o n i s reasonable. However, the f i n d i n g t h a t i n t e r c a l a t e s which remove e l e c t r o n d e n s i t y from the g r a p h i t e s u r f a c e w i l l a l s o enhance the a c t i v i t y of the g r a p h i t e would seem to i n d i c a t e t h at e i t h e r r a d i c a l anion or r a d i c a l c a t i o n formation on the b a s a l planes can lead to r a c e m i z a t i o n . N e v e r t h e l e s s , o n l y r a d i c a l anion formation i s c o n s i s t e n t with a mechanism i n v o l v -ing e l e c t r o n donation i n t o b i n a p h t h y l . I I I . THE INTERACTION OF RACEMIC AND OPTICALLY ACTIVE 1,11-BINAPHTHYL WITH RANEY NICKEL 57 A. INTRODUCTION Raney N i c k e l i s a p r a c t i c a l c a t a l y s t f o r r e d u c t i o n of o r -ganic compounds which i s prepared i n the l a b o r a t o r y by the a c t i o n of sodium hydroxide on a nickel-aluminum a l l o y . Q ] N i A l 2 + 6NaOH • N i + 2Na 3A10 3 + 3H 2 The r e a c t i o n produces a h i g h l y porous 'sponge' n i c k e l with hydrogen adsorbed on i t s s u r f a c e . The sodium aluminates which are a l s o produced may or may not be washed from the c a t a l y s t , depending on the method of p r e p a r a t i o n . The adsorbed hydrogen i s used f o r hydrogenation r e a c t i o n s . There are a wide v a r i e t y of methods that have been used to a f f e c t the r e a c t i o n of the a l l o y . The most popular are those 4 5 which produce the W s e r i e s of Raney N i c k e l c a t a l y s t s . These p r e p a r a t i o n s have been s t a n d a r d i z e d by Adkins and the a c t i v i t y of the r e s u l t i n g c a t a l y s t s compared i n t h e i r a c t i v i t y towards 4 6 4 7 - ' 3-naphthol. Dominguez et a l : and-Burgstahler and. AbdelrrRahman among o t h e r s , have devised t h e i r own c o n d i t i o n s f o r Raney N i c k e l p r e p a r a t i o n s . In a d d i t i o n , there are commercial p r e p a r a t i o n s 49 a v a i l a b l e which may be used as r e c e i v e d . In g e n e r a l , the d i f f e r e n t p r e p a r a t i o n s vary i n the method of a d d i t i o n of the a l l o y , the c o n c e n t r a t i o n of sodium hydroxide, the time and temperature of d i g e s t i o n , and the method of washing the c a t a l y s t . By changing these c o n d i t i o n s , c a t a l y s t s are ob-t a i n e d which can a f f e c t a wide v a r i e t y of r e d u c t i o n s at high or low pressures and i n a v a r i e t y of s o l v e n t s . For example, a W-2 58 c a t a l y s t has been used t o hydrogenate r e s o r c i n o l a t h i g h p r e s s u r e i n a l k a l i n e s o l u t i o n . ^ 0 O H 0 Raney N i (W-2) aq. NaOH, 1900 p s i H 9 ^ •OH 45-50 A c o m m e r c i a l l y p r e p a r e d c a t a l y s t has been used t o reduce the double bond o f p - a n i s y l b o r n y l e n e t o the e x o - d i h y d r i d e . ^ In t h i s case i t had been found t h a t a W-5 c a t a l y s t reduced the a r o m a t i c m o i e t y as w e l l . D e s u l f u r i z a t i o n w i t h o u t c o n c u r r e n t r e d u c t i o n o f an a r o m a t i c r i n g was a c h i e v e d by B u r g s t a h l e r and Abdel-Rahman by d e v e l o p i n g 48 t h e i r own p r e p a r a t i o n o f Raney N i c k e l . In a d d i t i o n t o the above examples, Raney N i c k e l - i n one o f i t s forms - has been shown t o be an e f f e c t i v e c a t a l y s t f o r the r e d u c t i o n o f a wide range o f double bonds, t r i p l e bonds, and f o r d e h a l o g e n a t i o n r e a c t i o n s . Degassed Raney N i c k e l has a l s o been 52 used as a c o u p l i n g agent i n the s y n t h e s i s o f 2 , 2 ' - b i p y r i d i n e . 59 Not a l l of the d i f f e r e n t types of Raney N i c k e l can a f f e c t the same r e d u c t i o n . However, there i s a p p a r e n t l y l i t t l e under-standing of how or why d i f f e r e n t methods of p r e p a r a t i o n should give d i f f e r e n t c a t a l y s t s . What i s known about the s t r u c t u r e of Raney N i c k e l c a t a l y s t s has been reviewed by Anderson. The a c t i v e c a t a l y s t s appear to always c o n t a i n r e s i d u a l aluminum both as metal and as aluminum oxide. The aluminum oxide i s found on the s u r f a c e of the n i c k e l with coverages v a r y i n g between 15 and 45% of the t o t a l s u r f a c e area. The n i c k e l i s found as l a r g e p a r t i c l e s (>100:nm) composed of smaller c r y s t a l l i t e s (2.5 - 15 nm) and with an e x t e n s i v e pore s t r u c t u r e . In a d d i t i o n , there i s some water bound to the a l u -minum oxides which on l y desorbs upon h e a t i n g . The n i c k e l c r y s t a l l i t e s have been suggested to a r i s e from the m i g r a t i o n of i n d i v i d u a l n i c k e l atoms f o l l o w i n g the l o s s of 53 aluminum from the a l l o y . The c r y s t a l l i t e s themselves have a high c o n c e n t r a t i o n of s u r f a c e d e f e c t s which decreases upon ex-tended time and temperature of p r e p a r a t i o n . No doubt t h i s i s of c o n s i d e r a b l e importance in determining the a c t i v i t y of a c a t a l y s t . Current t h e o r i e s regarding the a c t i v i t y of s o l i d c a t a l y s t s p o s t u l a t e that i t i s d i f f e r e n t types of s u r f a c e de-57 f e c t s that are r e s p o n s i b l e f o r c a t a l y t i c a c t i v i t y . Atoms at surface d e f e c t s w i l l tend to have fewer nearest neighbors and t h e r e f o r e have lower c o o r d i n a t i o n numbers than those atoms i n smooth c r y s t a l p l a n e s . I t i s the low c o o r d i n a t i o n number s i t e s 60 on the s u r f a c e which appear to be so a c t i v e i n breaking chemical bonds. In a d d i t i o n to s u r f a c e d e f e c t s , d i f f e r e n t c r y s t a l faces themselves can provide a d s o r p t i o n s i t e s which are e n e r g e t i c a l l y d i s t i n c t . In the case of n i c k e l , three d i f f e r e n t adsorbed 54 s t a t e s have been found f o r carbon monoxide on the <110> face 55 and two s t a t e s have been found f o r benzene on the <111> f a c e . L i k e w i s e , c e r t a i n types of d e f e c t s are more prone to occur on c e r t a i n c r y s t a l f a c e s , as i n the p r o d u c t i o n of stepped s u r f a c e s 5 8 on the low index faces of c e r t a i n metals. Any complete e x p l a n a t i o n f o r the d i f f e r e n t a c t i v i t y of Raney N i c k e l c a t a l y s t s w i l l c e r t a i n l y encompass a l l of the above. How-ever, as of t h i s date the p r e c i s e reasons why one method of pre-p a r a t i o n should produce a d i f f e r e n t c a t a l y s t than another method are not at a l l c l e a r . Because e a r l i e r work had shown t h a t e l e c t r o n donating s u r -faces would c a t a l y z e the r a c e m i z a t i o n of 1 , 1 1 - b i n a p h t h y l * and because of the a v a i l a b i l i t y and p r a c t i c a l importance of Raney N i c k e l , i t was decided to see i f and how Raney N i c k e l would i n -t e r a c t with racemic and o p t i c a l l y a c t i v e b i n a p h t h y l . A l l the Raney N i c k e l used was prepared a c c o r d i n g to the method of Burg-14 s t a h l e r and Abdel-Rahman as d e s c r i b e d by F i e s e r and F i e s e r . T h i s method of p r e p a r a t i o n was chosen because of i t s g e n e r a l use and because i t can be c a r r i e d out r a p i d l y and e a s i l y . * * 1,1'-binaphthyl w i l l be r e f e r r e d to as simply b i n a p h t h y l . ** T h i s c a t a l y s t had been used i n the past to d e s u l f u r i z e without the concurrent r e d u c t i o n of a benzene r i n g . 61 B. REDUCTION OF RACEMIC 1,1'-BINAPHTHYL WITH RANEY NICKEL To the b e s t o f our knowledge t h e r e has been no p r e v i o u s i n v e s t i g a t i o n i n t o the i n t e r a c t i o n o f b i n a p h t h y l w i t h the s u r -f a c e o f a n i c k e l c a t a l y s t . However, t h e r e are s e v e r a l s t u d i e s concerned w i t h the i n t e r a c t i o n o f b i n a p h t h y l w i t h o t h e r h e t e r o -geneous t r a n s i t i o n m e t a l c a t a l y s t s . Tn one case Copeland e t 59 a l passed b i n a p h t h y l over a number o f su p p o r t e d c a t a l y s t s a t 490 °C. They obse r v e d e i t h e r i s o m e r i z a t i o n or d e h y d r o c y c l i z a t i o n , depending on the c a t a l y s t . For a p l a t i n u m c a t a l y s t s u p p o r t e d on a l u m i n a , i s o m e r i z a t i o n t o 1,2'- and 2 , 2 1 - b i n a p h t h y l o c c u r r e d . 62 One case i n which a m o l e c u l e s t r u c t u r a l l y s i m i l a r t o b i n a p h -t h y l was t r e a t e d w i t h Raney N i c k e l has been r e p o r t e d by M i l l e r and Mann.^ 0 In t h e i r c a s e , t r e a t i n g 3 , 4 - d i h y d r o - l , 1 1 - b i n a p h t h y l w i t h Raney N i c k e l ( u n s p e c i f i e d o r i g i n ) i n r e f l u x i n g e t h a n o l gave the t e t r a h y d r o compound i n v e r y poor y i e l d . S t a r t i n g m a t e r i a l was a l s o r e c o v e r e d . A l t h o u g h these p r e v i o u s s t u d i e s had been done a t h i g h e r t e m p e r a t u r e s , i t was d e c i d e d t o b e g i n the i n i t i a l i n v e s t i g a t i o n a t 25 ° C * The s o l v e n t used was n-heptane. Samples were r e -moved p e r i o d i c a l l y from a s t i r r e d s u s p e n s i o n o f Raney N i c k e l i n a b i n a p h t h y l s o l u t i o n and the c a t a l y s t f i l t e r e d . The f i l t r a t e c o u l d then be a n a l y z e d by gas l i q u i d chromatography ( g l c ) . * T h i s temperature m i n i m i z e d e r r o r s due t o s o l v e n t e v a p o r a -t i o n and l o s s o f c a t a l y s t due t o bumping. S c a l e up r e a c t i o n s were done a t r e f l u x . 63 I t was found t h a t almost immediately upon a d d i t i o n of Raney N i c k e l to b i n a p h t h y l , four new peaks appeared on the g l c t r a c e i n a d d i t i o n to the b i n a p h t h y l peak. These peaks, a l l with r e -t e n t i o n times l e s s than that f o r b i n a p h t h y l , continued to grow at the expense of the b i n a p h t h y l . To put these r e s u l t s on a more q u a n t i t a t i v e b a s i s , the f i l t e r e d s o l u t i o n s were mixed 1:1 with a f r e s h s o l u t i o n of 4,4'-dimethyl-1,1'-binaphthyl (DMB) of a c o n c e n t r a t i o n approximately equal to the i n i t i a l b i n a p h t h y l c o n c e n t r a t i o n . Glc a n a l y s i s then gave an a d d i t i o n a l peak f o r DMB. The change i n c o n c e n t r a -t i o n of any of the components i n s o l u t i o n was then p r o p o r t i o n a l to the change i n the r a t i o of i t s peak area to that of the DMB peak. Fi g u r e 11 i l l u s t r a t e s how the r a t i o of peak areas - termed r e l a t i v e c o n c e n t r a t i o n - v a r i e s throughout the course of a t y p -i c a l r e a c t i o n . * The curves are t y p i c a l of those obtained when some r e a c t a n t ( i . e . binaphthyl) passes through three i n t e r m e d i -61 ates (curves I, I I , III) to g i v e some f i n a l product (curve I V ) . Thus the c o n c e n t r a t i o n of b i n a p h t h y l i s c o n s t a n t l y d e c r e a s i n g because of the o v e r a l l r e a c t i o n * * k B i n a p h t h y l ^ IV where k i s the o v e r a l l r a t e constant f o r l o s s of b i n a p h t h y l . The curves have not been adjusted f o r the d i f f e r e n t response of the flame i o n i z a t i o n d e t e c t o r to the d i f f e r e n t compounds. As w i l l be seen below, b i n a p h t h y l i s a l s o being l o s t due to a d s o r p t i o n . 700 F i g u r e 1 1 . P r o d u c t D i s t r i b u t i o n C u r v e s o f t h e I n t e r m e d i a t e s i n t h e R e d u c t i o n o f B i n a p h t h y l . 65 Likewise, the c o n c e n t r a t i o n of IV i n c r e a s e s s t e a d i l y at the same r a t e . Intermediates i n a r e a c t i o n show the g e n e r a l shape of curves I, I I , and I I I because t h e i r c o n c e n t r a t i o n at any time i s gov-erned by t h e i r r e l a t i v e r a t e s of formation and r e a c t i o n , such as i n A V B — ^ C where ra d J S = L = - k 2CBj The c o n c e n t r a t i o n of B w i l l i n c r e a s e u n t i l the c o n c e n t r a t i o n of A has decreased to the p o i n t where the r a t e of r e a c t i o n of B, k 2 [ j 3 [ ] , i s g r e a t e r than i t s r a t e of formation, k-^QT]. A f t e r that time the c o n c e n t r a t i o n of B decreases. F i g u r e 11 thus corresponds to a r e a c t i o n scheme shown i n Scheme 3. k, k 2 k k. B i n a p h t h y l =>• I »> II ^ I I I V I V Scheme 3 The h e i g h t of the curves are best understood i n terms of competitive a d s o r p t i o n on the same r e d u c t i o n s i t e s on the Raney N i c k e l s u r f a c e . Consider f i r s t o f a l l that the h e i g h t s of the curves are r e l a t i v e maxima and must s a t i s f y the c o n d i t i o n d = 0. (using the g e n e r a l equation [[5]) Under these c o n d i t i o n s / / 66 and i t can be seen that the h e i g h t of the curve at the maximum value depends on the r a t i o of the r a t e constants f o r formation and r e a c t i o n of the intermediate and a l s o on the c o n c e n t r a t i o n of the p r e c u r s o r . Since the r a t e constants i n our case are r a t e constants f o r c a t a l y z e d r e a c t i o n s , they are s u b j e c t to the i n -fluen c e of i n h i b i t o r s . For example, the presence of molecules which would compete s t r o n g l y f o r r e d u c t i o n s i t e s would decrease the value of k 2 i n equation [J5T] . Using t h i s approach, the r e l a t i v e h e i g h t s of the curves can now be understood i f we assume t h a t the s t r e n g t h of the adsorp-t i o n bond decreases i n the order binaphthyl>I>II>III>IV. I f we apply equation |]7] to two inte r m e d i a t e s from Scheme 3, we ob-t a i n k l and 3 The reason the maximum f o r Q l l ] i s so much higher i s t h a t the r a t e constant f o r r e a c t i o n of I I , k^, i s suppressed due to the i n h i b i t o r y e f f e c t of b i n a p h t h y l and the prec u r s o r I, while k 2 i s onl y suppressed by b i n a p h t h y l . The i n h i b i t o r y e f f e c t of b i n a p h t h y l p e r s i s t s u n t i l the b i n a p h t h y l c o n c e n t r a t i o n has dropped c o n s i d e r a b l y (150 min). The same arguments may be a p p l i e d to the other curves. 67 The f i n a l product IV was isolated and i d e n t i f i e d as the octahydro reduction product of binaphthyl.* IV Although the intermediates I, I I , and III were not isolate d , a l l the data i s consistent with a reaction path involving separate reduction of ind i v i d u a l double bonds. Assuming the least hin-dered double bonds are reduced f i r s t , the proposed structures for the intermediates are III 5,6,7,8,5',6',7',8'-octahydro-1,1•-binaphthyl 68 It i s interesting that in M i l l e r and Mann's reduction of 3,4-dihydro-l,1 1-binaphthyl^ 0 a similar reduction of the outside rings was not observed. It may be that the product formed, l,2,3,4-tetrahydro-l,l'-binaphthyi, possessed enough s t e r i c hindrance between the 2,8' and 2',8 positions to prevent the correct geometry of approach to the surface. The octahydro compound (previously unsynthesized) proved to be quite interesting in i t s own r i g h t . Its 270 MHz nmr spectrum had features which allowed determination of some conformational c h a r a c t e r i s t i c s of the molecule. The nmr spectrum 69 ( F i g u r e 12) shows two n e a r l y i d e n t i c a l p a i r s o f t r i p l e t s c e n-t e r e d a t 6 2.41 and <5 2.18. Both p a i r s have an i n t e g r a t i o n v a l u e o f 2 p r o t o n s and each c o r r e s p o n d s t o a p r o t o n from C8 and C8'.* Each p r o t o n e x p e r i e n c e s g e m i n a l c o u p l i n g ( J = 18 cps) w i t h the p r o t o n a t t a c h e d t o the same carbon (C8,8') and e q u a l v i c i n a l c o u p l i n g ( J = 7.0 cps) w i t h the two p r o t o n s on the ad-j a c e n t carbon (C7,7'). S i n c e c o u p l i n g w i l l depend on the d i -6 2 h e d r a l a n g l e between the c o u p l i n g p r o t o n s , a r i g i d c y c l o h e x e n e r i n g would not g i v e e q u i v a l e n t v i c i n a l c o u p l i n g between a p r o t o n on C8,8' and the p r o t o n s on C7,7'. However, i n a r a p i d l y f l i p -p i n g c y c l o h e x e n e r i n g the d i h e d r a l a n g l e s a l l become a p p r o x i -m a t e l y e q u a l and v i c i n a l c o u p l i n g w i t h the p r o t o n s on C7,7' i s the same.** The p r o t o n s on C8,8" a l s o e x p e r i e n c e average environments w i t h a r a p i d l y f l i p p i n g c y c l o h e x e n e r i n g , y e t because o f t h e i r c l o s e r p r o x i m i t y t o the a r o m a t i c r i n g i n the o p p o s i t e r i n g s y s -tem, t h e i r averages are markedly d i f f e r e n t . As a consequence, the two p r o t o n s e x p e r i e n c e d i f f e r e n t magnetic f i e l d s , have d i f -f e r e n t c h e m i c a l s h i f t s , and are r e s o l v a b l e i n t o s e p a r a t e s e t s o f t r i p l e t s . In c o n t r a s t , the p r o t o n s on C5,5' are not r e s o l v a b l e and show up as a m u l t i p l e t (<5 2.82). The f a c t t h a t the C8,8' P o s i t i o n s 8,8' are exchangeable w i t h a C2 a x i s and are t h e r e f o r e e q u i v a l e n t . S t r i c t l y s p e a k i n g , the p r o t o n s on C7,7' are n e i t h e r e q u i v a l e n t nor e n a n t i o t o p i c and, even w i t h f l i p p i n g , do not g i v e e x a c t l y the same c o u p l i n g . However, the d i f -f e r e n c e s were beyond the l i m i t o f d e t e c t i o n . 71 p r o t o n s are s h i f t e d u p f i e l d r e l a t i v e t o the C5,5' p r o t o n s a l s o i n d i c a t e s t h a t the C8,8' p r o t o n s must be e x p e r i e n c i n g a s t r o n g s h i e l d i n g e f f e c t due t o the r i n g c u r r e n t o f the o p p o s i t e aroma-t i c r i n g . Because the p r o t o n s on C8,8' are e x p e r i e n c i n g magnetic f i e l d s which are s u f f i c i e n t l y d i f f e r e n t t o p e r m i t r e s o l u t i o n , the o c t a h y d r o compound, l i k e b i n a p h t h y l i t s e l f , must have h i n -dered r o t a t i o n about the 1,1' bond. I f t h i s were n o t t r u e , the p r o t o n s would be e n a n t i o t o p i c due t o r a p i d r o t a t i o n about the 1,1' bond and thus would have the same c h e m i c a l s h i f t . * Our new compound s h o u l d a l s o , l i k e b i n a p h t h y l , e x i s t as two e n a n t i o m e r s . A l l o f t h i s d a t a drew us t o c o n c l u d e t h a t the o c t a h y d r o compound has the t w i s t e d ( c h i r a l ) c o n f o r m a t i o n shown i n F i g u r e 13 f o r one o f the e n a n t i o m e r s . 270 MHZ NMR P r o t o n (carbon no, s p l i t t i n g ) C2 (2 ' ) , d o u b l e t C3 (3 ' ) , 2 d o u b l e t s ( u n r e s o l v e d ) C4 (4 ' ) , d o u b l e t C5 (5 1 ) , m u l t i p l e t C6(6') , C7(7') , m u l t i p l e t C 8 ( 8 ' ) a , 2 t r i p l e t s C 8 ( 8 ' ) b , 2 t r i p l e t s C h e m i c a l C o u p l i n g S h i f t C o n s t a n t (PPin, 6) (cps) 6.88 7.11 7.06 2.82 1.73 2.41 2.18 7.5 7.5, 7.5 7.5 18, 7.0 18, 7.0 F i g u r e 13. S t r u c t u r e and 270 MHZ NMR Assignments o f 5,6,7,8,5',6',7',8'-Octahydro-1,1'-binaphthyl. * T h i s assumes t h a t the average c o n f o r m a t i o n would have the two r i n g systems c o p l a n a r . 72 C. THE SPONTANEOUS RESOLUTION OF 5,6,7,8,51,6',7',8'-OCTAHYDRO-1,1'-BINAPHTHYL The deduction that the octahydro compound should e x i s t as enantiomers was confirmed i n a remarkable i n c i d e n t which oc-cu r r e d d u r i n g the work up of the r e a c t i o n mixture (see E x p e r i -mental s e c t i o n ) . A s c a l e up of the i n i t i a l r e a c t i o n was done using racemic b i n a p h t h y l . A f t e r f i l t e r i n g o f f the Raney N i c k e l , the s o l v e n t was evaporated to give a c l e a r o i l which, a f t e r i n i t i a t i n g c r y s t a l i z a t i o n with an i c e bath, was placed i n a f r e e z e r o v e r n i g h t . T h i s gave c l e a r c r y s t a l l i n e prisms and a c o n s i d e r a b l e amount of u n c r y s t a l l i z e d o i l . Out of c u r i o s i t y the o p t i c a l a c t i v i t y of the o i l was checked and, to our s u r p r i s e , i t was a c t i v e , with Qof] 2 ** = +4.8! L i k e -3 6 5 wise, the b e a u t i f u l c r y s t a l s had an opposite but lower s p e c i f i c r o t a t i o n , \~a~]24 = -1.3. A repeat of the experiment gave y ' — — ' 3 6 5 s i m i l a r r e s u l t s but the sign s of the r o t a t i o n s were changed, i . e . f o r the o i l , Ta -! 2 4 = -4.8, and f o r the c r y s t a l s , u - 1 3 6 5 [ > ! 2 4 = + i . i . - 1 3 t> 5 I f the c r y s t a l s so obtained were r e c r y s t a l l i z e d from hot et h a n o l , the s p e c i f i c r o t a t i o n of the c r y s t a l l i z e d m a t e r i a l was zero. However, when a small amount (35 mg) of the r e c r y s t a l -l i z e d m a t e r i a l was d i s s o l v e d i n n-heptane (4 mil) and the s o l v e n t 73 e v a p o r a t e d over f o u r weeks, l a r g e c r y s t a l s c o u l d be grown. One such c r y s t a l , when d i s s o l v e d i n one mil o f n-heptane, gave a r o t a t i o n o f a = - 0 . 0 1 0 and a h a l f l i f e f o r r a c e m i z a t i o n o f 3 6 5 17 h r s . These r e s u l t s i n d i c a t e d t h a t one c r y s t a l l i n e form o f the o c t a h y d r o compound must be a r a c e m i c m i x t u r e where t h e r e are d i s c r e t e c r y s t a l s o f each e n a n t i o m e r . ^ I f t h i s were not t r u e , a s i n g l e c r y s t a l would not have had any r o t a t i o n . A l s o , s i n c e the compound r a c e m i z e s a t a d e t e c t a b l e r a t e , the o p t i c a l a c t i -v i t y must be due t o the compound i t s e l f and not an i m p u r i t y . An i m p u r i t y would not have m a i n t a i n e d i t s a c t i v i t y t hrough the c o u r s e o f the r e a c t i o n - two weeks i n r e f l u x i n g n-heptane. I t was c o n c l u d e d t h a t the c r y s t a l s o f the o c t a h y d r o compound had i n f a c t s p o n t a n e o u s l y r e s o l v e d . An attempt was made t o determine i f h i g h e r t e m p e r a t u r e s would l e a d t o r a p i d r o t a t i o n about the 1 , 1 ' bond. I f r o t a t i o n about t h a t bond becomes r a p i d a t h i g h e r t e m p e r a t u r e s , any two p r o t o n s a t t a c h e d t o a s i n g l e carbon would become e n a n t i o t o p i c because the average c o n f o r m a t i o n o f the m o l e c u l e would be f l a t . In o t h e r words, a l l the carbons would l i e i n the same p l a n e . In t h a t case the two p a i r s o f t r i p l e t s would c o a l e s c e i n t o a s i n g l e t r i p l e t w i t h an i n t e g r a t i o n v a l u e o f 4 p r o t o n s . However, no d e t e c t a b l e change i n the 400 MHz NMR was d e t e c t a b l e over the range 27 t o 160 °C. T h i s i n d i c a t e d t h a t a c o n s i d e r a b l e b a r r i e r to r o t a t i o n e x i s t e d , even a t h i g h e r t e m p e r a t u r e s . * * Rate c o n s t a n t s which can be o b t a i n e d by t h i s method u s u a l l y f a l l i n the range 1 0 " 1 t o 1 0 5 s e c - 1 . 9 1 74 The h i g h b a r r i e r t o r o t a t i o n can be e x p l a i n e d by c o n s i d e r -i n g the o c t a h y d r o compound t o be a s u b s t i t u t e d b i p h e n y l , V. R y The e f f e c t o f t h i s type o f s u b s t i t u t i o n on the r a t e o f r a c e m i z a -7 6 t i o n has been w e l l s t u d i e d and r e v i e w e d . U n f o r t u n a t e l y a spe-c i f i c case f o r R = R' = CI^CH^ has not been s t u d i e d , nor has R = R' = CH^. These two would be s i m i l a r i n many r e s p e c t s t o the o c t a h y d r o m o l e c u l e . N e v e r t h e l e s s , the i m p o r t a n t f a c t o r i n these systems i s the l e n g t h o f the bond t o the R group and the s i z e o f the R' group. The l a r g e r the bond t o R, the g r e a t e r i s the s t e r i c h i n d r a n c e encountered w i t h the o r t h o hydrogen on the o p p o s i t e benzene r i n g as the m o l e c u l e c o n v e r t s from one enantiomer t o the o t h e r . The e f f e c t o f a l a r g e R 1 i s t o ' b u t t r e s s ' the R group, making i t even more d i f f i c u l t f o r R and H t o p a s s . In our c a s e , the methylene group a t C8 i s not o n l y pushed out (the b u t t r e s s e f -f e c t ) but i t i s a l s o h e l d out by the r i g i d s k e l e t o n o f the c y c l o -hexene system. I t i s not p o s s i b l e f o r C8 t o r o t a t e more than c a . 60° t o f a c i l i t a t e r a c e m i z a t i o n . More i m p o r t a n t , the C8 -CIO bond cannot bend i n w i t h o u t i n t r o d u c i n g bond s t r a i n somewhere 75 e l s e i n the c y c l o h e x e n e r i n g . I t i s the bending o f t h i s p a r -7 6 t i c u l a r bond which i s paramount f o r f a c i l e r a c e m i z a t i o n . The e f f e c t o f the c y c l o h e x e n e r i n g i n p r e v e n t i n g bending of the C8 - CIO bond must be d r a m a t i c . I t i s known t h a t the a d d i -t i o n o f the bond l e n g t h s o f the o r t h o s u b s t i t u e n t s which c r o s s 7 6 i s a good e s t i m a t i o n o f the b a r r i e r t o r o t a t i o n . For example, the 2 , 6 - d i n i t r o - 2 ' , 6 1 - d i m e t h o x y b i p h e n y l VI - one o f the slower r a c e m i z i n g b i p h e n y l s - has a h a l f l i f e o f 98 min a t 25 °C. 7^ o 7 The sum o f the bond l e n g t h s f o r C-NC>2 and C-OCH3 t o t a l s 3.37 A. By c o n t r a s t , i f we take as the C8 - CIO bond l e n g t h the v a l u e o f o 7 9 1.55 A o b t a i n e d f o r t e t r a c h l o r o t e t r a l i n ,* and add the v a l u e 78 of 0.94 f o r the p r o t o n - C2 bond l e n g t h , the t o t a l i s o n l y 2.49 A, y e t the h a l f l i f e a t room temperature i s on the o r d e r o f a day. A p p a r e n t l y when no bond bending i s p o s s i b l e even s r a a l l s t e r i c e f f e c t s a r e c r i t i c a l . T e t r a l i n i t s e l f would p r o v i d e a b e t t e r c o m p a r i s o n , but i s a l i q u i d a t room t e m p e r a t u r e . A p p a r e n t l y f o r t h i s reason the c r y s t a l s t r u c t u r e o f the t e t r a c h l o r o d e r i v a t i v e has been s t u d i e d . As the author p o i n t s o u t , 9 the v a l u e o f 1.55 A i s the same as t h a t f o r ca r b o n - c a r b o n bond l e n g t h s i n c y c l o -hexane and would t h e r e f o r e appear t o be a good v a l u e f o r the C9 - CIO bond i n t e t r a l i n . o H 3 C 0 N02 H 3 C O NO2 VI 76 One l a s t p o i n t should be made regarding the octahydro com-pound. S t r i c t l y speaking i t d i d not spontaneously r e s o l v e . When a system spontaneously r e s o l v e s , i t generates an o v e r a l l c h i r a l i t y without the i n t e r v e n t i o n of an e x t e r n a l c h i r a l i n f l u -8 0 ence. The best s t u d i e d example of t h i s i s b i n a p h t h y l i t s e l f . In that case an ampule of the melt may c r y s t a l l i z e as a pre-dominance of e i t h e r one enantiomer or the o t h e r . Because the b i n a p h t h y l molecules can r e a d i l y i n t e r c o n v e r t i n the melt, the c r y s t a l l i z a t i o n process can ' p u l l ' a l l the molecules over to one enantiomeric type. The net r e s u l t i s an ampule with a measur-able degree of o v e r a l l o p t i c a l a c t i v i t y . In the present case the rate of i n t e r c o n v e r s i o n of the enan-tiomers i s very low (ti = 17 hr at 24.5°). There i s t h e r e f o r e no e f f i c i e n t means of i n t e r c o n v e r s i o n and the number of R and S enantiomers remains the same. Consequently, s i n c e the s t a r t i n g m a t e r i a l was racemic, the o v e r a l l o p t i c a l a c t i v i t y i n the f l a s k i s zero. . With t h i s important c o n s i d e r a t i o n i n mind, the term 'spon-taneously r e s o l v e d ' was only c a r e f u l l y used. D. TREATMENT OF OPTICALLY ACTIVE 1,1'-BINAPHTHYL WITH RANEY NICKEL When an o p t i c a l l y a c t i v e s o l u t i o n (a = -0.700) of b i -3 6 5 naphthyl i n n-heptane was added to a s l u r r y o f Raney N i c k e l , the course of the r e a c t i o n c o u l d be followed by p o l a r i m e t r y (decrease i n o p t i c a l a c t i v i t y ) or by g l c (decrease i n 77 c o n c e n t r a t i o n o f b i n a p h t h y l ) . When t h i s was done, i t was found t h a t the o p t i c a l a c t i v i t y of the s o l u t i o n q u i c k l y d e c r e a s e d , u l t i m a t e l y r e a c h i n g a c o n s t a n t v a l u e of zer o l o n g b e f o r e the b i n a p h t h y l c o n c e n t r a t i o n had gone to z e r o . As Table VI i n d i -c a t e s , t h i s l o s s o f o p t i c a l a c t i v i t y c o u l d not be accounted f o r by the t o t a l l o s s i n b i n a p h t h y l by a d s o r p t i o n or r e d u c t i o n . L i k e w i s e , the slow c o n c u r r e n t u n c a t a l y z e d r a c e m i z a t i o n ( t ^ = 493 min) c o u l d not account f o r the l o s s i n o p t i c a l a c t i v i t y . T able VI a l s o shows t h a t of the t o t a l amount o f b i n a p h t h y l l o s t , l e s s than 29% c o u l d be a t t r i b u t e d t o r e d u c t i o n p r o d u c t s . Table VI R e s u l t s o f T r e a t i n g a S o l u t i o n o f O p t i c a l l y A c t i v e B i n a p h t h y l w i t h Raney N i c k e l f o r 115 m i n u t e s 3 percentage o f o p t i c a l a c t i v i t y l o s t 95% perc e n t a g e o f b i n a p h t h y l l o s t due t o 66% a d s o r p t i o n and r e d u c t i o n p e rcentage o f the t o t a l b i n a p h t h y l l o s s which <29% can be a t t r i b u t e d t o r e d u c t i o n a I n n-heptane a t 25 °C. [ [ b i n a p h t h y l ] = 0.025 M [ [ N i ] = 1 0 0 (mg/m£) These r e s u l t s i n d i c a t e d t h a t , f i r s t o f a l l , i n a d d i t i o n to the r e d u c t i o n p r o c e s s , t h e r e must be an e x t e n s i v e a d s o r p t i o n process o c c u r r i n g . T h i s i s necessary to account fo r the binaph t h y l l o s s beyond that a t t r i b u t a b l e to r e d u c t i o n . Secondly, be-cause l o s s i n b i n a p h t h y l c o u l d not account f o r the l o s s i n o p t i c a l a c t i v i t y , e i t h e r the Raney N i c k e l was c a t a l y z i n g the r a c e m i z a t i o n r e a c t i o n or o p t i c a l l y a c t i v e r e d u c t i o n products were being formed which had a l a r g e r and o p p o s i t e s p e c i f i c r o t a t i o n than the o r i g i n a l b i n a p h t h y l . The l a t t e r e x p l a n a t i o n can be e l i m i n a t e d because the s o l u t i o n smoothly reaches a f i n a l c onstant value of zero. I t was t h e r e f o r e concluded that there were three d i f f e r e n t types of i n t e r a c t i o n s o c c u r r i n g on the Raney N i c k e l s u r f a c e : r e d u c t i o n , r a c e m i z a t i o n , and a d s o r p t i o n . A q u e s t i o n which n a t u r a l l y a r i s e s i s whether and to what extent the three types of s u r f a c e i n t e r a c t i o n s are r e l a t e d . Oftentimes s u r f a c e r e a c t i o n s which lead to s e v e r a l products can be e x p l a i n e d by the e x i s t e n c e of a s i n g l e a c t i v e s i t e . For example, many hydrocarbon i s o m e r i z a t i o n r e a c t i o n s - double bond mig r a t i o n s and s k e l e t a l rearrangements - are due to r e v e r s i b l e 65 steps i n the hydrogenation mechanism or the e x i s t e n c e of d i -vergent pathways f o r the rearrangement of an adsorbed i n t e r -6 6 mediate. In the present case the b i n a p h t h y l molecule might have r e v e r s i b l y adsorbed on the s u r f a c e and been reduced i n a 64 t y p i c a l H o r i u t i - P o l a n y i mechanism (Scheme 5). I f the binaph-t h y l were adsorbed i n a symmetrical conformation such as the t r a n s - c o p l a n a r conformation shown, then i t c o u l d desorb as e i t h e r enantiomer. One a c t i v e s i t e thus accounts fo r adsorp-t i o n , r e d u c t i o n , and r a c e m i z a t i o n . 79 Scheme 5 On the o t h e r hand, i f the s u r f a c e had i n d i v i d u a l s i t e s f o r r e d u c t i o n , r a c e m i z a t i o n , and a d s o r p t i o n , then we might have ex p e c t e d t h a t they c o u l d be s e p a r a t e l y stopped by a p p r o p r i a t e p o i s o n i n g . S e l e c t i v e p o i s o n i n g o f one o f s e v e r a l s u r f a c e r e -a c t i o n s has been used by o t h e r a u t h o r s as c o n c l u s i v e e v i d e n c e t h a t the d i f f e r e n t r e a c t i o n s are o c c u r r i n g a t d i f f e r e n t s u r f a c e 67 68 69 s i t e s . ' I t i s g e n e r a l l y f e l t t h a t the p o i s o n becomes s e l e c t i v e l y adsorbed a t the a c t i v e s i t e , b l o c k i n g f u r t h e r ad-s o r p t i o n o f the s u b s t r a t e . I t s h o u l d be p o i n t e d o u t t h a t p o i s o n -i n g e x p e r i m e n t s do not e x c l u d e the p o s s i b i l i t y t h a t one o f sev-e r a l r e a c t i o n pathways o f an a d s o r b a t e (such as b i n a p h t h y l i n Scheme 5) may become i n d i v i d u a l l y and s e l e c t i v e l y b l o c k e d by a 80 poison. However, t h i s p o s s i b i l i t y seems never to have been en-t e r t a i n e d as a p l a u s i b l e mechanism f o r the a c t i o n of pois o n s . The f o l l o w i n g s e c t i o n c o n s i d e r s the r e s u l t s of t r e a t i n g an o p t i c a l l y a c t i v e s o l u t i o n of b i n a p h t h y l with poisoned ( s u l f u r or dodecanethiol) Raney N i c k e l . E. TREATMENT OF OPTICALLY ACTIVE 1,1'-BINAPHTHYL WITH POISONED RANEY NICKEL When a s o l u t i o n of o p t i c a l l y a c t i v e b i n a p h t h y l was added to a s l u r r y of poisoned Raney N i c k e l , the r e s u l t s were d i f f e r e n t from those shown i n Table VI. Table VII l i s t s the r e s u l t s f o r a number of r a t i o s of poison - i n t h i s case elemental s u l f u r -to n i c k e l . At a low r a t i o the r e d u c t i o n was completely stopped, but the l o s s of o p t i c a l a c t i v i t y was s t i l l g r e a t e r than the amount adsorbed. T h i s i n d i c a t e d t h a t the rac e m i z a t i o n process was s t i l l o c c u r r i n g i n the absence of the r e d u c t i o n p r o c e s s . At a higher r a t i o of s u l f u r to n i c k e l , the a d s o r p t i o n process alone accounted f o r the l o s s i n o p t i c a l a c t i v i t y . F i n a l l y , s u f -f i c i e n t s u l f u r would completely poison not only the c a t a l y t i c a c t i v i t y of the n i c k e l (both f o r r a c e m i z a t i o n and r e d u c t i o n ) , but a l s o the a b i l i t y to adsorb b i n a p h t h y l . On the b a s i s of the d i s c u s s i o n i n the previous s e c t i o n , these r e s u l t s were i n -t e r p r e t e d to mean t h a t e i t h e r there are three d i f f e r e n t s i t e s on the s u r f a c e of Raney N i c k e l which can i n t e r a c t with binaph-t h y l i n three d i f f e r e n t ways, or there are three d i f f e r e n t a c t i v i t i e s a s s o c i a t e d with a s i n g l e s i t e . 81 Table VII The E f f e c t of S u l f u r on the A c t i v i t y of Raney N i c k e l mg sulfur/mg Ni r e d u c t i o n l o s s i n o p t i c a l a c t i v i t y a d s o r p t i o n 0.0063 0 68% 47% 0.019 0 - 8% 8% 0.025 0 0 0 a I n n-heptane at 25 °C. |]binaphthyl] = 0 .0020 M [[Ni] =50 (mg/ml) time = 20 min With one e x c e p t i o n , the r e s u l t s i n Table VII are q u a l i t a -t i v e l y the same as those obtained f o r a l l the Raney N i c k e l used throughout t h i s work. I f i n the p r e p a r a t i o n of the Raney N i c k e l (see Experimental s e c t i o n ) the c a t a l y s t were washed with tap water rather than d i s t i l l e d water, the r e s u l t i n g product would adsorb b i n a p h t h y l but would n e i t h e r reduce nor racemize i t . Dodecanethiol was a l s o used as poison and gave r e s u l t s q u a l i t a t i v e l y the same as s u l f u r . However, at high c o n c e n t r a -t i o n s of t h i o l , the r e a c t i o n suspension turned dark brown and a new peak appeared on g l c t r a c e s . A l s o , dark s o l u t i o n s were more d i f f i c u l t to analyze by p o l a r i m e t r y . Since the a c t u a l s t u d i e s to be d i s c u s s e d d i d not r e q u i r e such high c o n c e n t r a t i o n s of t h i o l , t h i s poison could be used interchangeably with s u l f u r . 82 The r a t i o s of s u l f u r to n i c k e l i n Table VII are not the minimum values r e q u i r e d to achieve the e f f e c t s shown. For ex-ample, a r a t i o of 0.0050 may have been s u f f i c i e n t to completely stop the r e d u c t i o n process. However, because of d i f f i c u l t i e s i n h andling the n i c k e l i n a s l u r r y , i t was not p o s s i b l e to r e -produce the same c a t a l y t i c a c t i v i t y of each new batch of n i c k e l , nor to o b t a i n the same a c t i v i t y of c a t a l y s t i n s u c c e s s i v e ex-periments. T h i s was probably due to f a c t o r s such as weight, p a r t i c l e s i z e d i s t r i b u t i o n , and t r a c e contaminants which made exact r e p r o d u c i b i l i t y very d i f f i c u l t . Consequently, measuring minimum q u a n t i t i e s was an impossible task. I t w i l l be seen l a t e r i n t h i s t h e s i s t h at t h i s problem a l s o made other q u a n t i -t a t i v e s t u d i e s of n i c k e l r a ther d i f f i c u l t . N e v e r t h e l e s s , the sequence of p o i s o n i n g f i r s t the r e d u c t i o n , then the racemiza-t i o n , and f i n a l l y the a d s o r p t i o n was always the same i n v a r i o u s batches of c a t a l y s t . With the p o s s i b i l i t y t h a t the a c t i v i t y of the n i c k e l c o u l d be b e t t e r c o n t r o l l e d , i t was decided to take a c l o s e r look at each process as i t occurred on an a p p r o p r i a t e l y poisoned c a t a -l y s t . The r e d u c t i o n process was d i s c u s s e d i n a previous s e c t i o n and the f o l l o w i n g s e c t i o n s w i l l d e a l with the r a c e m i z a t i o n and ad s o r p t i o n processes, r e s p e c t i v e l y . F. THE POISONED RANEY NICKEL CATALYZED RACEMIZATION OF 1,1'-BINAPHTHYL A f t e r p r e p a r i n g a batch of Raney N i c k e l and determining what r a t i o of poison to n i c k e l was necessary to stop the 83 r e d u c t i o n , i t was p o s s i b l e to study the c a t a l y z e d r a c e m i z a t i o n of a s o l u t i o n of o p t i c a l l y a c t i v e b i n a p h t h y l without i n t e r f e r -ence from l o s s of b i n a p h t h y l by formation of r e d u c t i o n products. T h i s made k i n e t i c a n a l y s i s o f the c a t a l y z e d r a c e m i z a t i o n a sim-p l i f i e d task. F i l t e r e d s o l u t i o n s from the r e a c t i o n f l a s k c o u l d be analyzed f o r o p t i c a l a c t i v i t y and the data t r e a t e d i n a manner analogous to that f o r the carbon c a t a l y z e d r e a c t i o n s . F i g u r e 14 shows a number of t y p i c a l f i r s t order k i n e t i c p l o t s f o r the c a t a l y z e d r a c e m i z a t i o n . I t i s seen t h a t , f o l l o w -ing an i n i t i a l curved p o r t i o n , the r e a c t i o n f o l l o w s good f i r s t order behaviour. In some runs, r a t e constants obtained from the s t r a i g h t l i n e p o r t i o n of the graph showed r a t e enhancements of a facto'r of ten over the uncatalyzed r e a c t i o n . The i n i t i a l curved p o r t i o n o f the k i n e t i c p l o t i s e x p l a i n e d by r e f e r e n c e to Fig u r e 15. Here the f r a c t i o n of the t o t a l amount adsorbed ( r i g h t y - a x i s , determined by g l c ) i s p l o t t e d along with the f i r s t order k i n e t i c p l o t ( l e f t y - a x i s , determined by p o l a r -i m e t r y ) . From the curves i t can be seen that the cu r v a t u r e i n the r a c e m i z a t i o n p l o t stops at the same time a d s o r p t i o n s t o p s . The c u r v a t u r e i n the r a c e m i z a t i o n p l o t i s thus accounted f o r by a n o n - f i r s t order a d s o r p t i o n process o c c u r r i n g at the same time as a f i r s t order r a c e m i z a t i o n process, i . e . For two concurrent r e a c t i o n s , one f i r s t order and the other n o n - f i r s t o r d e r , 1 ! 1—I Time (min) 50 100 F i g u r e 14. F i r s t Order K i n e t i c P l o t s for the Poisoned Raney N i c k e l Catalyzed Racemization of B i n a p h t h y l i n n-Keptane at 25.0 °C. [[Binaphthyl] = 0.050 M |]Nij = 0.40 (#) , 0.35 (A), and 0.30 (A) mil s l u r r y mJt/total volume Time (min) 9 0 270 F i g u r e 15. F i r s t Order K i n e t i c P l o t and F r a c t i o n Adsorbed f o r the Poisoned Raney N i c k e l C a t a l y z e d Racemization of B i n a p h t h y l . CO 86 B n o n - l s t order B Scheme 6 the o v e r a l l r a t e i s n o n - f i r s t order i n A. D o ] 2S£L = k i r a + k 2 o r ] n A f t e r the n o n - f i r s t order process reaches e q u i l i b r i u m , the r e a c t i o n shows f i r s t order behaviour, as i s seen i n F i g u r e 15. In c o n j u n c t i o n with t h i s f i n d i n g , a c a t a l y s t which was s t i r r e d with racemic b i n a p h t h y l before being used f o r a k i n e t i c run gave a very good f i r s t order p l o t throughout the course of the k i n e t i c run (Figure 16). 71 As has been pointed out by Low, most chemisorptions w i l l not f o l l o w the usual mass a c t i o n f u n c t i o n s i n v o l v i n g i n t e g r a l or f r a c t i o n a l powers of c o n c e n t r a t i o n . I t i s not s u r p r i s i n g , then, that attempting to superimpose a slow a d s o r p t i o n process on a f i r s t order k i n e t i c p l o t would lead to c u r v a t u r e . However, a f t e r a d s o r p t i o n has reached e q u i l i b r i u m , what c o n d i t i o n s must be met i n order to o b t a i n f i r s t order k i n e t i c s ? The s i m p l e s t f i r s t order k i n e t i c scheme would correspond to that found f o r the carbon c a t a l y z e d r e a c t i o n . R e c a l l that i n that case the 17 mechanism i n v o l v e d simple a d s o r p t i o n - d e s o r p t i o n . The adsorbed b i n a p h t h y l was p o s t u l a t e d to be i n a t r a n s - c o p l a n a r conformation F i g u r e 16. The E f f e c t on the F i r s t Order K i n e t i c P l o t of P r e t r e a t i n g Poisoned N i c k e l with B i n a p h t h y l . [[Binaphthyl] = 0 .0025 M C N i I ! =37.7 (mg/mJl) Temperature: 25.0 °C Raney 03 88 To determine what other f e a t u r e s these two systems had i n common, a more r i g o r o u s k i n e t i c i n v e s t i g a t i o n was begun. T h i s s t a r t e d by attempting to f i n d how the f i r s t order r a t e constant, k, was e f f e c t e d by temperature, poison, and c o n c e n t r a t i o n of s u b s t r a t e and c a t a l y s t . Table V I I I c o n t a i n s the v a r i a t i o n of k with these parameters. Only one g e n e r a l f e a t u r e of the c a t a l y z e d r a c e m i z a t i o n emerged from Table V I I I . That i s that although the shapes of the f i r s t order k i n e t i c p l o t s were r e p r o d u c i b l e , s p e c i f i c curves themselves were not. For example, e n t r i e s 6 and 7 were thought to be i d e n t i c a l k i n e t i c runs, yet times of a d s o r p t i o n and values of k d i f f e r e d d r a m a t i c a l l y . L i k e w i s e , runs 40 and 41 appeared to d i f f e r i n the c o n c e n t r a t i o n of n i c k e l , yet gave i d e n t i c a l k v a l u e s . T h i s d i f f i c u l t y was no doubt due to problems mentioned e a r l i e r : i t was impossible to o b t a i n p r e c i s e l y the same a c t i -v i t y of c a t a l y s t f o r any two experiments. Thus the t o t a l num-ber of s u r f a c e s i t e s would vary and one would always be p o i s o n -ing more or l e s s s i t e s than we thought were pres e n t . T h i s problem p e r s i s t e d even when the method of d i s p e n s i n g the n i c k e l was changed (see Experimental s e c t i o n ) and precluded any f u r t h e r k i n e t i c i n v e s t i g a t i o n s . The c o n c l u s i o n s which can be drawn are that 1) racemiza-t i o n c a t a l y s i s proceeds i n the absence of r e d u c t i o n ; 2) a f t e r a slow a d s o r p t i o n process i s complete, r a c e m i z a t i o n f o l l o w s f i r s t order k i n e t i c s , and; 3) f i r s t order k i n e t i c s corresponds to the s i m p l e s t a d s o r p t i o n - d e s o r p t i o n mechanism. Table V I I I Tabulated K i n e t i c Results f o r the Poisoned Raney N i c k e l C a t a l y z e d Racemization of Binaphthyl Run no. Temperature Amount of C N i ] b [Binaphthyl] Time of k d catalyst (°C) Poison 3 (xl0 3M) Adsorption 0 (min - 1xl0 3) batch 1 40.0 0 0 2 40.0 0.20 5/15 3 40.0 0.20 1/7 4 40.0 0.20 2/9 5 40.0 0.20 2/9 6 40.0 0.20 3/10 7 40.0 0.20 3/10 8 40.0 0.20 2/10 9 40.0 0.20 2/10 10 40.0 0.20 3/10 11 40.0 0.066 3/10 12 25.0 0 0 13 25.0 0.20 3/10 14 25.0 0.20 •3/10 15 25.0 0.20 3/10 16 25.0 0.20 5/10 17 25.0 0.20 4/10 18 25.0 0.20 7/10 19 25.0 0.20 6/10 20 25.0 0.20 4/10 21 25.0 0.20 4/10 continued on the following page 15.0 0 8.7 -3.3 <30 e LH-6-5 7.1 0 8.7 LH-6-5 5.6 0 22 LH-6-5 5.5 0 8.7 LH-6-5 5.0 25 8.7 LH-6-5 5.0 4 76 LH-6-5 12.0 0 8.7 LH-6-5 5.0 0 8.7 LH-6^5 5.0 20 8.7 LH-6-5 5.0 115 8.7 LH-6-19 12.5 0 1.4 -5.0 0 e LH-6-19 8.3 25 1.4 LH-6-19 5.0 20 12 LH-6-19 5.0 14 6.5 LH-6-19 5.0 40 1.9 LH-6-19 5.0 7 6.5 LH-6-19 5.0 12 16 LH-6-19 5.0 40 5.2 LH-6-19 5.0 15 6.7 LH-6-19 oo Run no. Temperature (°C) Amount of Poison^ E N i I I g [Binaphthyl] Time of k (xl0 3M) Adsorption 0 (min _ 1xl0 3) catalyst batch 22 23 24 25 26 27 28 29 30 31 32 33 34. 35: 36; 37; 38: 39; 4 Of 4 i f 42r 25.0 0 12 5.0 30 1.4 LH-6-65 25.0 0 18 5.0 30 1.4 LH-6-65 25.0 0 29 5.0 30 1.4 LH-6-65 25.0 0.010 34 2.5 6 1.4 LH-6-81 25.0 0.010 114 2.5 0 1.4 LH-6-81 25.0 0.0050 18 2.5 10 1.4 LH-6-81 25.0 0.0050 43 2.5 5 1.4 LH-6-81 25.0 0.0050 67 2.5 10 1.4 LH-6-81 25.0 0.0050 56 1.3 15 1.4 LH-6-81 25.0 0.0050 100 2.5 25 26 LH-6-81 25.0 0.0050 124 2.5 5 16 LH-6-81 25.0 0.0050 77 2.5 50 2.2 LH-6-81 25.0 0.0050 100 2.5 0 39 LH-6-81 25.0 0.0050 97 2.5 0 28 LH-6-81 25.0 0.0050 78 2.5 0 22 LH-6-81 25.0 0.0050 38 2.5 0 2.8 LH-6-81 25.0 0.0050 125 2.5 0 5.2 LH-6-81 25.0 0.0050 77 2.5 0 1.4 LH-6-81 25.0 0.050 126 1.2 0 4.7 LH-7-5 25.0 0.050 178 1.2 0 4.7 LH-7-5 25.0 0.050 208 1.2 0 26 LH-7-5 91 Expressed as (mg sulfur/mJl c a t a l y s t s l u r r y ) . Expressed as (m£ c a t a l y s t slurry/m£ t o t a l volume). Determined from the curved p o r t i o n of 1st order r a c e m i z a t i o n k i n e t i c p l o t . From 1st order k i n e t i c p l o t , t i < 20 min. Expressed as (mg sulfur/mg Raney N i ) . Expressed as (mg/ml). P r e t r e a t e d by s t i r r i n g with h a l f the b i n a p h t h y l f o r 90 min. 92 G. THE ADSORPTION OF RACEMIC 1,11-BINAPHTHYL ON POISONED RANEY NICKEL As was p r e v i o u s l y p o i n t e d out, both the r e d u c t i o n and r a c e -m i z a t i o n a c t i v i t y of Raney N i c k e l was poisoned before the ad-s o r p t i v e a c t i v i t y was poisoned. T h i s allowed the a d s o r p t i o n process to be s t u d i e d independent o f . t h e r e d u c t i o n and racemi-z a t i o n . T h i s s e c t i o n w i l l d e s c r i b e the a d s o r p t i o n f e a t u r e s of b i n a p h t h y l on a d o d e c a n e t h i o l poisoned Raney N i c k e l . F i g u r e 17 c o n t a i n s a number of moles adsorbed versus time curves f o r v a r i o u s i n i t i a l c o n c e n t r a t i o n s of b i n a p h t h y l and otherwise constant c o n d i t i o n s . The curves r e c a l l the problem encountered i n the r a c e m i z a t i o n study. That i s , although the shapes of the curves are r e p r o d u c i b l e , s p e c i f i c curves them-s e l v e s are not. Thus curves a and b were thought to be run under i d e n t i c a l c o n d i t i o n s but d i f f e r e d i n the t o t a l amount adsorbed (the h e i g h t of the curves) and i n the r a t e of a d s o r p t i o n (the shape of the c u r v e s ) . Again, the problem i s most l i k e l y due to d i f f i c u l t i e s i n handling the n i c k e l s l u r r y . F i g u r e 18 shows the a d s o r p t i o n isotherm f o r b i n a p h t h y l on poisoned Raney N i c k e l . T h i s isotherm i s not a true isotherm i n the sense that i t p e r t a i n s to a s c r u p u l o u s l y c l e a n and degassed 70 s u r f a c e over a very wide range of b i n a p h t h y l c o n c e n t r a t i o n s . The s u r f a c e i s contaminated by aluminum and aluminum oxides i n a d d i t i o n to the d o d e c a n e t h i o l which was i n t e n t i o n a l l y added. The dangers i n attempting to i n t e r p r e t a d s o r p t i o n isotherm on F i g u r e 17. Moles Adsorbed versus Time f o r the Adsorption of Bi n a p h t h y l on Poisoned w Raney N i c k e l . <3" o CD J O O CO "D O to CD O E 0 CNi] Ratio mg dodecanethiol/mg Ni Temperature Solvent IOO(mg/ml) 6.1 x 1CT2 7.8 °C n-heptane 10 20 30 40 Ibinaphthyl] ( x 1 0 4 M ) F i g u r e 18... A d s o r p t i o n Isotherm f o r Binaphthyl on Poisoned Raney N i c k e l . 95 " i m p e r f e c t l y d e f i n e d , o f t e n m y s t e r i o u s l y produced" s u r f a c e s have been po i n t e d out. N e v e r t h e l e s s , i n s o f a r as t h i s isotherm r e p r e s e n t s that of b i n a p h t h y l on the a d s o r p t i o n (versus reduc-t i o n and racemization) s i t e s , i t i s Langmuir i n type. F i g u r e 19 c o n t a i n s the a d s o r p t i o n isobar f o r the system. The curve was obtained by m a i n t a i n i n g a suspension of poisoned Raney N i c k e l i n a b i n a p h t h y l s o l u t i o n at v a r i o u s temperatures. T h i s allowed d e t e r m i n a t i o n of the r e v e r s i b i l i t y of the adsorp-t i o n . The moles adsorbed was determined at 280°, 240°, and 210°K. Upon b r i n g i n g the suspension back up to 280°, the same value f o r moles adsorbed was obtained as i n the f i r s t case. A f i n a l de-t e r m i n a t i o n was made at 320°. I t should be p o i n t e d out that with a d i f f e r e n t batch of c a t a l y s t q u a l i t a t i v e l y d i f f e r e n t r e s u l t s were obtained f o r the i s o b a r . In that case a d s o r p t i o n d i d not i n c r e a s e with a decrease i n temperature below room temperature, a p p a r e n t l y because s a t u r -a t i o n had been a t t a i n e d . However, the adsorbed b i n a p h t h y l c o u l d be desorbed by r e f l u x i n g the suspension. T h i s s i t u a t i o n would correspond to a s h i f t to the r i g h t of the curve i n F i g u r e 19. The k i n e t i c s , isotherm, and isobar obtained are t y p i c a l of 70 71 those found f o r other types of c h e m i s o r p t i o n . ' I t i s un-f o r t u n a t e , though, that s p e c i f i c curves were not r e p r o d u c i b l e . There are r e l a t i v e l y few examples of chemisorptions which are both slow and e x t e n s i v e , p a r t i c u l a r l y from the s o l u t i o n phase. R e p r o d u c i b i l i t y would have allowed b e t t e r c h a r a c t e r i z a t i o n of the 7 system, e s p e c i a l l y with regard to entropy and heat of a d s o r p t i o n . o CD jQ v . O CO TD O S 10-O E LNi • = 46 (mg/ml) mgdodecanethiol/mg Ni = 3.5x10" 2 Solvent = n-heptane Temperature(°K) 250 300 350 19 A d s o r p t i o n Isobar f o r Bi n a p h t h y l on Poisoned Raney N i c k e l , 97 Ne v e r t h e l e s s , some th i n g s are e v i d e n t from the data which were c o l l e c t e d . The f a c t t h a t the a d s o r p t i o n isotherm was Langmuir over the range s t u d i e d means that there are not a wide v a r i e t y of s i t e s which d i f f e r i n t h e i r enthalpy of a d s o r p t i o n . This i s inherent i n the assumptions of the Langmuir-type i s o -therms and would be c o n s i s t e n t with the b i n a p h t h y l being adsorbed at a number of l i m i t e d types of s i t e s on the s u r f a c e . The i s o -bar, although not c o n f i r m i n g t h i s p o i n t of view, i s c o n s i s t e n t with i t . A v a r i e t y of su r f a c e s i t e s f o r a d s o r p t i o n can le a d to an isobar which c o n t a i n s s e v e r a l maxima and minima and would be 70 very d i s t i n c t from the type we obt a i n e d . Low has summarized a number of f i n d i n g s concerning slow chemisorptions i n the f o l l o w i n g way: "...slow a d s o r p t i o n r e a l l y occurs 'on top o f 1 contaminants i f the s o l i d i s not r i g o r o u s l y 71 cleaned and kept f r e e from i m p u r i t i e s . " Although he continues to p o i n t out that some c l e a n s u r f a c e s do show slow chemisorp-t i o n , i t i s tempting to a t t r i b u t e the a d s o r p t i o n of b i n a p h t h y l on Raney N i c k e l to the aluminum oxide which u s u a l l y covers 15 to 45% of the t o t a l s u r f a c e . ^ Besides being c o n s i s t e n t with the k i n e t i c s , t h i s c o n c l u s i o n would a l s o be c o n s i s t e n t with the known s o r p t i v e p r o p e r t i e s of aluminum o x i d e s . H. CONCLUSION We have found that a Raney N i c k e l c a t a l y s t w i l l c a t a l y z e both the ra c e m i z a t i o n and the r e d u c t i o n of b i n a p h t h y l . In a d d i -t i o n , there i s an ex t e n s i v e a d s o r p t i o n process which o c c u r s . 98 These t h r e e i n t e r a c t i o n s can be c o n t r o l l e d by c a r e f u l p o i s o n i n g o f the c a t a l y s t w i t h s u l f u r o r d o d e c a n e t h i o l and each p r o c e s s then s t u d i e d s e p a r a t e l y . A l t h o u g h extended s t u d i e s were hampered by problems o f r e -p r o d u c i b i l i t y , the accumulated d a t a i n d i c a t e s e v e r a l t h i n g s . The r e d u c t i o n proceeds through t h r e e i n t e r m e d i a t e s t o g i v e the o c t a h y d r o b i n a p h t h y l IV as the f i n a l p r o d u c t . IV The r a c e m i z a t i o n r e a c t i o n f o l l o w s f i r s t o r d e r k i n e t i c s a f t e r an i n i t i a l n o n - f i r s t o r d e r p e r i o d . The n o n - f i r s t o r d e r p e r i o d i s due t o the a d s o r p t i o n p r o c e s s o c c u r r i n g c o n c u r r e n t l y . F i r s t o r d e r k i n e t i c s c o r r e s p o n d s t o the s i m p l e s t a d s o r p t i o n - d e s o r p t i o n mechanism f o r the r a c e m i z a t i o n . The a d s o r p t i o n i s s i m p l e Lang-muir i n t y p e , i s r e v e r s i b l e , and may i n v o l v e aluminum o x i d e s adsorbed on the Raney N i c k e l . The d i f f e r e n t a c t i v i t i e s o f the Raney N i c k e l can be ex-p l a i n e d i n one o f two ways. One p o s s i b i l i t y i s t h a t a s i n g l e c a t a l y t i c s i t e has t h r e e d i f f e r e n t a c t i v i t i e s . I t might be pos-s i b l e f o r a p o i s o n t o more e f f e c t i v e l y s t o p the r e d u c t i o n b e f o r e s t o p p i n g the r a c e m i z a t i o n , and t o s t o p the r a c e m i z a t i o n b e f o r e the a d s o r p t i o n (Scheme 7) . 99 r a c e m i z a t i o n stopped second stopped I • f i r s t " J " Scheme 7 r e d u c t i o n However, a much s i m p l e r e x p l a n a t i o n i s t h a t t h e r e are t h r e e d i f -f e r e n t s i t e s on the s u r f a c e , each one r e s p o n s i b l e f o r a s e p a r a t e type o f i n t e r a c t i o n w i t h b i n a p h t h y l . M u l t i p l e s u r f a c e s i t e s a re o f t e n e x p r e s s e d e x p e r i m e n t a l l y i n the v a r i e t y o f s t a t e s i n which an a d s o r b a t e may be found. Examples o f t h i s a re seen i n the a d s o r p t i o n o f hydrogen and 73 74 carbon monoxide on n i c k e l and e t h y l e n e on a l u m i n a . Our case appears t o be one o f a r e l a t i v e l y few c a s e s where the presence o f d i f f e r e n t s u r f a c e s i t e s appears t o be r e s p o n s i b l e f o r the c a t a l y s i s o f d i f f e r e n t r e a c t i o n s o f the same a d s o r b a t e . Another c a t a l y s t which has shown t h i s behaviour i s y alumina, which has separate s i t e s f o r o l e f i n i s o m e r i z a t i o n and v i n y l i c hydrogen-deuterium exchange. 7^ The o r i g i n of the m u l t i p l e s u r f a c e s i t e s most l i k e l y l i e s i n the very heterogeneous s u r f a c e obtained i n the p r e p a r a t i o n of the c a t a l y s t . The s u r f a c e a l s o c o n t a i n s adsorbed i m p u r i t i e s , such as aluminum o x i d e s , which may impart a d d i t i o n a l c a t a l y t i c or a d s o r p t i o n p r o p e r t i e s to the Raney N i c k e l . 101 IV. THE PLATINUM (ADAMS' CATALYST) CATALYZED RACEMIZATION OF 1,11-BINAPHTHYL A. INTRODUCTION Platinum metal has been the s u b j e c t of e x t e n s i v e s t u d i e s , both as a metal and because of i t s e x t e n s i v e use as a hydro-92 genation c a t a l y s t . A p r a c t i c a l form of c a t a l y t i c platinum which i s used e x t e n s i v e l y i n o r g a n i c s y n t h e s i s i s produced i n  s i t u by the r e d u c t i o n of platinum oxide (Adams' C a t a l y s t ) by hydrogen i n a s u i t a b l e s o l v e n t . Platinum c a t a l y s t s produced i n t h i s manner have been used i n the s o l u t i o n phase to c a t a l y z e a wide range of hydrogenation and h y d r o g e n o l y s i s r e a c t i o n s . These in c l u d e the r e d u c t i o n of carbon-carbon double and t r i p l e bonds, aromatic r i n g s , ketones, and v a r i o u s n i t r o g e n c o n t a i n i n g func-t i o n a l i t i e s , as w e l l as the hy d r o g e n o l y s i s of a c i d c h l o r i d e s , 92 halogens, and o t h e r s . Much of the u t i l i t y of Adams' C a t a l y s t comes from the commercial a v a i l a b i l i t y of the platinum oxide, i t s r e s i s t a n c e to d e a c t i v a t i o n d u r i n g extended storage, and the ease of producing the a c t i v e form of the c a t a l y s t . The platinum oxide o r i g i n a l l y prepared by Adams was at f i r s t thought to have the formula PtO2"H20> Adams suggested that hydrogen r e d u c t i o n of t h i s oxide produced a lower oxide which was r e s p o n s i b l e f o r 94 95 the c a t a l y s i s . More recent work by Cahen and Ibers has shown that the platinum oxide i s a c t u a l l y a mixture of m e t a l l i c platinum, ( p o s s i b l y hydrated), and a sodium platinum bronze, Na^t-^O^ . (The sodium o r i g i n a t e s from the s y n t h e t i c process used f o r Pt02 production.) The platinum oxide i s reduced to m e t a l l i c platinum and water by hydrogen, but the Na^t^O^ 102 remains unchanged by the r e d u c t i o n . P a r t i c l e diameters f o r the reduced product are i n the micrometer range and sur f a c e areas 2 are g e n e r a l l y i n the range 0.1 to 1.0 (m / g ) . Although unreduced Adams' C a t a l y s t can be st o r e d f o r months 9 2 or even years without l o s s of a c t i v i t y , the a c t i v i t y of the reduced c a t a l y s t i s very changeable and v a r i e s c o n s i d e r a b l y with the pH of the s o l v e n t and may be modified d r a m a t i c a l l y by the a d d i t i o n of a d d i t i v e s such as a l k a l i s a l t s . For example, Baker and Schuetz u n s u c c e s s f u l l y attempted to reduce benzene i n dioxane or e t h a n o l at 135 atm and 1 8 0 ° . 9 ^ When the s o l v e n t was changed to a c e t i c a c i d , the r e a c t i o n was complete i n f i f t e e n minutes at room temperature and 125 atm. S i m i l a r r a t e enhancements i n the presence of a c i d s have been repo r t e d f o r the r e d u c t i o n of c h o l -97 e s t e r o l d e r i v a t i v e s . When both h y d r o g e n o l y s i s and hydrogena-t i o n may occur on the same molecule, the p r o p o r t i o n of hydro-g e n o l y s i s product may be inc r e a s e d with i n c r e a s e d s o l v e n t a c i d i t y , 98 as i n the case of cinnamyl a l c o h o l hydrogenation, or decreased by i n c r e a s i n g the sodium content of the c a t a l y s t , as i n the case 93 of the r e d u c t i o n of c h o l e s t - 4 - e n - 3 3 ~ o l . The r e d u c t i o n of ni t r o g e n c o n t a i n i n g f u n c t i o n a l i t i e s o f t e n r e q u i r e s the presence of a c i d s , presumably to protonate any amine which might o t h e r -wise poison the c a t a l y s t . In some cases the e f f e c t of s o l v e n t a c i d i t y can be a t t r i -buted to the r e a c t i o n of the a c i d with the s u b s t r a t e or product. As mentioned above, p r o t o n a t i o n of an amine w i l l stop i t s p o i s o n -ing of the c a t a l y s t . L i k e w i s e , p r o t o n a t i o n of the group to be 103 cleaved i n a h y d r o g e n o l y s i s r e a c t i o n may f a c i l i t a t e hydrogenoly-s i s with a p p a r e n t l y l i t t l e e f f e c t on a concurrent hydrogenation. T h i s would e x p l a i n the v a r i a t i o n i n h y d r o g e n o l y s i s to hydrogen-a t i o n product r a t i o s with changing a c i d i t y . However, i n the case of r a t e enhancements of benzene hydrogenation, and i n cases where a d d i t i v e s other than a c i d s , such as a l k a l i s a l t s , a l t e r the s e l e c t i v i t y of the c a t a l y s t , i t appears that i t i s the c a t a l y s t i t s e l f which i s changed by the a d d i t i v e s . S e v e r a l authors have suggested t h a t the a l k a l i content of the reduced c a t a l y s t has an i n h i b i t o r y e f f e c t on d i f f e r e n t r e d u c t i o n r e a c t i o n s . ^ 9 ' 1 0 0 ' This i n h i b i t i o n may be stopped by the a d d i t i o n of a c i d , which per-haps d i s s o l v e s the a l k a l i . In c o n j u n c t i o n with t h i s i d e a , wash-ing a pre-reduced c a t a l y s t prepared i n a c e t i c a c i d or methanol w i l l produce a c a t a l y s t which i s a c t i v e towards benzene hydro-9 9 genation. There have been no suggestions put f o r t h r e g a r d i n g the p r e c i s e mechanism of i n h i b i t i o n . The p r e v i o u s work (Chapter III) with Raney N i c k e l had shown that o p t i c a l l y a c t i v e 1,1'-binaphthyl* can i n t e r a c t with a t r a n -s i t i o n metal c a t a l y s t i n a way which w i l l l ead to r a c e m i z a t i o n without concurrent r e d u c t i o n . I t t h e r e f o r e appeared of i n t e r e s t to determine i f t h i s were a g e n e r a l f e a t u r e of t r a n s i t i o n metal c a t a l y s t s which could be extended to Adams' C a t a l y s t . The f o l -lowing s e c t i o n s d e s c r i b e v a r i o u s k i n e t i c r e s u l t s f o r the p l a t i -num (reduced Adams' C a t a l y s t ) c a t a l y z e d r a c e m i z a t i o n of binaph-t h y l . 1,1'-Binaphthyl w i l l be r e f e r r e d to simply as b i n a p h t h y l . 104 B. THE PLATINUM CATALYZED RACEMIZATION OF 1,11-BINAPHTHYL A f t e r reducing platinum oxide i n ethanol on a s l o p i n g mani-f o l d hydrogenation apparatus, the c a t a l y z e d r a c e m i z a t i o n of b i -naphthyl could be s t u d i e d i n a manner analogous to the carbon c a t a l y z e d r a c e m i z a t i o n (see Experimental s e c t i o n ) . I t was found that small amounts (ca l.Omg/mJl) of the oxide would, a f t e r r e -d u c t i o n , q u i c k l y racemize a s o l u t i o n of o p t i c a l l y a c t i v e binaph-t h y l with no concurrent r e d u c t i o n or d e t e c t a b l e a d s o r p t i o n . * The r e s u l t s were the same whether e i t h e r f r e s h platinum oxide were used or platinum oxide which had been opened and s t o r e d f o r s e v e r a l y ears. L i k e the other c a t a l y z e d r a c e m i z a t i o n s s t u d i e d i n t h i s t h e s i s , the platinum c a t a l y z e d r e a c t i o n showed good f i r s t order k i n e t i c s , as seen i n F i g u r e 20 f o r s e v e r a l d i f f e r e n t runs. I f a batch of c a t a l y s t were allowed to stand i n the hydrogenation apparatus f o r s e v e r a l days a f t e r a k i n e t i c run, r e p r o d u c i b l e rate constants c o u l d be obtained by removing some of the op-t i c a l l y i n a c t i v e supernatant and r e p l a c i n g i t with a f r e s h (op-t i c a l l y a c t i v e ) s o l u t i o n of b i n a p h t h y l . T h i s r e p r o d u c i b i l i t y allowed some q u a n t i t a t i v e k i n e t i c s t u d i e s to be done (see below). During the r e d u c t i o n of the oxide the c a t a l y s t appeared to go through s e v e r a l p h y s i c a l changes. Before r e d u c t i o n the powder would form a very f i n e suspension when r a p i d l y s t i r r e d . W i t h in the f i r s t h a l f hour of r e d u c t i o n the c a t a l y s t coagulated * A d s o r p t i o n and r e d u c t i o n were determined by g a s - l i q u i d chromatographic a n a l y s i s . CM + ' b i . o -uncatalyzed 2.9x10~*M 5.0x10"*M 1.0xlO"3M [Binaphthyl] CPtD Temperature Solvent = as shown = 1.0(mg/ml) = 25.0 °C = 100% EtOH time (min) 100 200 300 F i g u r e 2 0 . F i r s t Order K i n e t i c P l o t f o r the Platinum Catalyzed Racemization of B i n a p h t h y l . o 106 i n t o l a r g e clumps and adsorbed g r e a t e r than 50% of the t o t a l hydrogen adsorbed. These l a r g e p a r t i c l e s i n turn would, a f t e r n e a r l y a day of continued s t i r r i n g under hydrogen, again break up i n t o a very f i n e suspension. I t was decided to determine at which p o i n t d u r i n g the r e -d u c t i o n the c a t a l y s t became a c t i v e and to see how the a c t i v i t y c o r r e l a t e d with the p h y s i c a l changes the c a t a l y s t was undergoing. Fig u r e 21 i s a f i r s t order k i n e t i c p l o t i n which the time a x i s corresponds to the time of r e d u c t i o n . (Platinum oxide i t s e l f i s not c a t a l y t i c . ) The graph i s a l s o d i v i d e d i n t o s e c t i o n s which correspond to the p h y s i c a l c o n d i t i o n ( f i n e powder versus coagu-l a t e d p a r t i c l e s ) of the c a t a l y s t at v a r i o u s times. The r e a c t i o n o b v i o u s l y slows down as the p a r t i c l e s clump together and then i n c r e a s e s i n r a t e as the p a r t i c l e s again form a f i n e powder. T h i s i s best e x p l a i n e d i n terms of a l o s s i n s u r f a c e area due to p a r t i c l e c o a g u l a t i o n , although i t may be that there i s a chemical change r e s p o n s i b l e f o r the f l u c t u a t i o n . Perhaps even more i n t e r e s t i n g i s the f a c t t h a t the c a t a l y s t ap-pears to become q u i t e a c t i v e immediately upon r e d u c t i o n . T h i s i m p l i e s t h a t the a c t i v e s i t e s f o r b i n a p h t h y l r a c e m i z a t i o n are c r e a t e d immediately upon r e d u c t i o n and do not r e q u i r e e x t e n s i v e r e d u c t i o n of the bulk oxide. F o l l o w i n g t h i s i n i t i a l work, i t was decided to pursue an i n v e s t i g a t i o n i n t o the k i n e t i c s of the c a t a l y z e d r e a c t i o n and to determine whether the r e a c t i o n was s e n s i t i v e to simple mole-c u l e s which are known to be reduced by the c a t a l y s t . 2.0-(\J + sr. Si 6 1.0-C PARTICULES COAGULATE PARTICLES BREAKING UP AFTER 16 HOURS REDUCTION t ime(min) 120 240 960 1080 F i g u r e 2 1 . F i r s t Order K i n e t i c P l o t for the Platinum Catalyzed Racemization of Bi n a p h t h y l Using Time of Reduction as the Time A x i s . 108 C. THE DEPENDENCE OF THE CATALYZED RATE ON 1,1'-BINAPHTHYL AND PLATINUM CONCENTRATIONS Changing the c o n c e n t r a t i o n of c a t a l y s t or s u b s t r a t e had to be accomplished without t r a n s f e r r i n g the platinum and r i s k i n g p o i s o n i n g by oxygen or other contaminants. In the case of the c a t a l y s t c o n c e n t r a t i o n , t h i s was done by adding a known volume of equimolar b i n a p h t h y l s o l u t i o n to the f l a s k at the end of a k i n e t i c run. A new run could then be s t a r t e d at a new, reduced c a t a l y s t c o n c e n t r a t i o n but the same b i n a p h t h y l c o n c e n t r a t i o n . To change the b i n a p h t h y l c o n c e n t r a t i o n without e f f e c t i n g the c a t a l y s t c o n c e n t r a t i o n , the c a t a l y s t was allowed to s e t t l e to the bottom of the f l a s k at the end of a k i n e t i c run. A measured volume of supernatant was then removed and r e p l a c e d with the same volume of a higher c o n c e n t r a t i o n b i n a p h t h y l s o l u -t i o n . A f t e r c a l c u l a t i n g the d i l u t i o n f a c t o r , a k i n e t i c run could be s t a r t e d at a higher b i n a p h t h y l c o n c e n t r a t i o n but the same platinum c o n c e n t r a t i o n . F i g u r e 22 i l l u s t r a t e s how the f i r s t order r a t e constant kobs G a n g e s as a f u n c t i o n of the b i n a p h t h y l c o n c e n t r a t i o n . The dependence of kQ^s on the c o n c e n t r a t i o n of b i n a p h t h y l i s the 17 same as that found f o r the carbon c a t a l y z e d r e a c t i o n . As the bi n a p h t h y l c o n c e n t r a t i o n i s i n c r e a s e d and the c o n c e n t r a t i o n of c a t a l y s t remains the same, a l a r g e number of both R and S b i -naphthyl molecules compete f o r a l i m i t e d number of ra c e m i z a t i o n s i t e s and the predominant mode of ra c e m i z a t i o n i s the uncatalyzed r e a c t i o n . uncatalyzed rate • 1 1 1 1 1.0 2.0 3.0 4.0 Binaphthyl concentration (mM) o F i g u r e 2 2 . D e p e n d a n c e o f kQ^s o n B i n a p h t h y l C o n c e n t r a t i o n f o r t h e P l a t i n u m C a t a l y z e d ^ R a c e m i z a t i o n o f B i n a p h t h y l . 110 The i n t e r p r e t a t i o n of the dependence of the r a t e constant on the platinum c o n c e n t r a t i o n i s not so s t r a i g h t f o r w a r d . Using the method d e s c r i b e d above, the c a t a l y z e d r e a c t i o n was run over four platinum c o n c e n t r a t i o n s ranging from 0.12 to 0.75 (mg/mJL). A l l the f i r s t order k i n e t i c p l o t s f o r these runs are shown t o -gether i n F i g u r e 23. Despite the f a c t t h a t the c a t a l y s t concen-t r a t i o n was changed by a f a c t o r g r e a t e r than s i x , F i g u r e 23 shows that the r a t e constant, as determined from the negative of the slope of the f i r s t order p l o t , remained e s s e n t i a l l y un-changed . There are other examples where the rat e of a c a t a l y z e d r e -a c t i o n i s independent of the c o n c e n t r a t i o n of the heterogeneous c a t a l y s t . However, these are always i n s t a n c e s i n which the t r a n s p o r t of a r e a c t a n t gas through a l i q u i d phase to the s u r -face of the c a t a l y s t i s the r a t e determining step i n the c a t a l y -102 t i c r e a c t i o n . As pointed out by Roberts, i n cases where t r a n s p o r t of the gas across the g a s - l i q u i d i n t e r f a c e i s r a t e determining, the r e a c t i o n r a t e w i l l not depend on the c a t a l y s t c o n c e n t r a t i o n , but rather w i l l depend on f a c t o r s which i n f l u -ence d i f f u s i o n across the g a s - l i q u i d i n t e r f a c e . These f a c t o r s i n c l u d e s t i r r i n g r a t e , r e a c t o r d e s i g n , and the c o n c e n t r a t i o n of the r e a c t a n t gas i n the gas phase. There are s e v e r a l c h a r a c t e r i s t i c s of the b i n a p h t h y l r e a c -t i o n which d i s t i n g u i s h i t from other r e a c t i o n s which are inde-pendent of c a t a l y s t c o n c e n t r a t i o n . Most important, the platinum c a t a l y z e d r a c e m i z a t i o n of b i n a p h t h y l i s not a r e a c t i o n which CM + a i.o-a . uncatalyzed A d" A WO i A • _° £ 0 C Binaphthyl J = 1.0x10"3M Temperature = 25.0 °C Solvent = 100% EtOH time(min) 5 0 100 150 F i g u r e 23. Dependance of k o b s on Platinum Concentration for the Platinum C a t a l y z e d Racemization of B i n a p h t h y l . C P t J = ° - 7 5 O f 0.43 <•) , 0.23 ( A ) , and 0.12 (#) (mg/m£) 112 consumes a r e a c t a n t gas. Since there i s no d e t e c t a b l e r e d u c t i o n d u r i n g the course of the c a t a l y s i s , there i s no consumption of hydrogen. Gas t r a n s p o r t i s thus not a f a c t o r which would be rate determining i n our case. In c o n j u n c t i o n with t h i s , a typ-i c a l k i n e t i c run was done under hydrogen, f o l l o w e d by another run under argon using the same c a t a l y s t and r e a c t i o n s c o n d i t i o n s . The r a t e s of the two r e a c t i o n s were i d e n t i c a l . A l s o , the platinum c a t a l y z e d r e a c t i o n was independent of the s t i r r i n g r a t e . By i n c r e a s i n g the area of l i q u i d - g a s i n t e r -f a c e , i n c r e a s e d a g i t a t i o n w i l l i n c r e a s e the r a t e of r e a c t i o n s whose rate determining step i s d i f f u s i o n across t h i s i n t e r f a c e . Although the s t i r r i n g speeds t e s t e d o n l y extended through the range achieved with a v a r i a b l e speed magnetic s t i r r e r , the r a t e of a k i n e t i c run was never changed by i n c r e a s i n g or d e c r e a s i n g the s t i r r i n g speed during a run. T h i s i s a l s o c o n s i s t e n t with a r e a c t i o n which i s not a f f e c t e d by d i f f u s i o n c o n t r o l l e d f a c t o r s . How then can t h i s p e c u l i a r k i n e t i c e f f e c t be explained? One p o s s i b i l i t y i s t h a t a s o l u b l e r a c e m i z a t i o n c a t a l y s t i s formed during the r e d u c t i o n of platinum oxide and i t i s only s l i g h t l y s o l u b l e i n the e t h a n o l s o l v e n t . Then even at low platinum c o n c e n t r a t i o n s , the s o l u t i o n w i l l be s a t u r a t e d with the c a t a l y s t and i n c r e a s i n g the platinum c o n c e n t r a t i o n w i l l have no e f f e c t on the c o n c e n t r a t i o n of the a c t u a l c a t a l y s t . However, the c a t a l y s i s c o u l d be completely stopped by f i l t e r i n g the c a t -a l y s t (under an i n e r t atmosphere) or by a l l o w i n g the s o l i d 113 platinum to completely s e t t l e out of the s o l u t i o n . T h i s would not be c o n s i s t e n t with c a t a l y s i s by a homogeneous c a t a l y s t . In an attempt to determine i f a more complicated k i n e t i c scheme might somehow account f o r the lack of dependence of the rate on platinum c o n c e n t r a t i o n , the simple k i n e t i c scheme used for the carbon ' and Raney N i c k e l (see Chapter III) c a t a l y z e d racemization of b i n a p h t h y l was extended to i n c l u d e an a d d i t i o n a l step. T h i s step i n v o l v e d the formation of a c t i v e s i t e s f o r r a c e m i z a t i o n by the a d s o r p t i o n of b i n a p h t h y l on s i t e s otherwise i n a c t i v e towards r a c e m i z a t i o n . U n f o r t u n a t e l y , t h i s ' a c t i v a t i o n mechanism' d i d not g i v e a r a t e e x p r e s s i o n which would e x p l a i n our r e s u l t s . Reaction schemes more e l a b o r a t e than t h i s d i d not seem reasonable and so f u r t h e r k i n e t i c a n a l y s i s was stopped. The very p e c u l i a r lack of r a t e dependence on c a t a l y s t con-c e n t r a t i o n remains an enigma. I t i s worth n o t i n g that a s i m i l a r case has been found i n t h i s l a b o r a t o r y f o r the carbon c a t a l y z e d 103 h y d r o l y s i s of a methyl phosphate e s t e r of b i n a p h t h o l which i s a l s o a r e a c t i o n i n which there i s no apparent gas d i f f u s i o n processes i n v o l v e d . As i n the p r e s e n t case, there was no appar-ent k i n e t i c or p h y s i c a l e x p l a n a t i o n f o r the lack of dependence of r a t e on c a t a l y s t c o n c e n t r a t i o n . In order to determine how the r a c e m i z a t i o n s i t e s were r e -l a t e d to the r e d u c t i o n s i t e s f o r simple hydrogenation r e a c t i o n s - and to perhaps shed some l i g h t on the p e c u l i a r k i n e t i c behav-iour - the e f f e c t of oxygen, cyclohexene, and cyclohexane on the course of the c a t a l y z e d r e a c t i o n was i n v e s t i g a t e d . The r e s u l t s of these s t u d i e s are presented i n the next s e c t i o n . 114 D. THE EFFECT OF OXYGEN, CYCLOHEXENE, AND CYCLOHEXANE ON THE PLATINUM CATALYZED RACEMIZATION OF 1,1'-BINAPHTHYL In order to i n v e s t i g a t e the e f f e c t of oxygen, cyclohexene, and cyclohexane on the platinum c a t a l y z e d r a c e m i z a t i o n of b i -naphthyl, a k i n e t i c run was begun i n the usual manner and, a f t e r one h a l f l i f e , a small q u a n t i t y of the a d d i t i v e was slowly i n -j e c t e d i n t o the s t i r r e d s o l u t i o n . The e f f e c t of the a d d i t i v e was then seen as a d e v i a t i o n of the f i r s t order k i n e t i c p l o t from the usual s t r a i g h t l i n e behaviour. Fi g u r e 24 i l l u s t r a t e s how the course of the c a t a l y z e d r e -a c t i o n i s e f f e c t e d by oxygen. The presence of oxygen i n the r e a c t i o n s o l u t i o n completely but t e m p o r a r i l y poisons the c a t a -l y z e d r e a c t i o n . The le n g t h of time f o r which c a t a l y s i s i s h a l t e d i s p r o p o r t i o n a l to the amount of oxygen i n j e c t e d i n t o the s o l u t i o n . In F i g u r e 25 the e f f e c t of cyclohexene on the r e a c t i o n i s shown. In c o n t r a s t to oxygen, cyclohexene has an i n h i b i t o r y , not a p o i s o n i n g e f f e c t . A l s o , the e f f e c t i s not t r a n s i e n t but rather permanent. The amount by which the r e a c t i o n r a t e i s reduced i s p r o p o r t i o n a l to the amount of cyclohexene i n j e c t e d i n t o the s o l u t i o n . I t was determined by g a s - l i q u i d chromatography that the cyclohexene i n j e c t e d i n t o the r e a c t i o n f l a s k was immediately reduced to cyclohexane. The r e d u c t i o n of cyclohexene from the s o l u t i o n phase by platinum i s thought to proceed through a Temperature = 25.0 °C Solvent = 100% EtOH time (min) 100 2 0 0 300 4 0 0 F i g u r e 24. E f f e c t of A i r on the F i r s t Order K i n e t i c P l o t f o r the Platinum C a t a l y z e d Racemization of B i n a p h t h y l . h-1 CR 1 = 0.94mg/ml) Temperature = 25.0 °C Solvent = 100% EtOH I , 1 r— time (min) 90 180 270 F i g u r e 25. E f f e c t of Cyclohexene on the F i r s t Order K i n e t i c P l o t f o r the Platinum C a t a l y z e d Racemization of B i n a p h t h y l . i — 1 t—• 117 64 l (Scheme 8) . H o r i u t i - P o l a n y i mechanism i n which the a d s o r p t i o n of the a l -kene i s i r r e v e r s i b l e H 2 • 2* ^ 2 H — * -1 \ / k2 \ / C=C +2* —=-|fc-C—C— / \ i t ' k ' » * -3 * H V C— C v + H z I 1 * H % > C - c 6 2* -4 H H (1) (2) (3) (4) Scheme 8 The q u e s t i o n a r i s e s whether the i n h i b i t o r y e f f e c t of cyclohexene i s due to a d s o r p t i o n of the reduced product, cyclohexane, by way of the reverse of step (4) i n Scheme 8, or whether the c y c l o -hexene i s being adsorbed on r a c e m i z a t i o n s i t e s which are d i f -f e r e n t from the r e d u c t i o n s i t e s ; Only i n the former case would one expect to see i n h i b i t o r y e f f e c t s of cyclohexane s i m i l a r to those seen f o r cyclohexene. In F i g u r e 26 the e f f e c t s of cyclohexane on the c a t a l y z e d r a c e m i z a t i o n of b i n a p h t h y l are shown. I t i s c l e a r by comparing F i g u r e s 6 and 7 t h a t the i n h i b i t o r y f e a t u r e s of the two com-pounds are the same. By the argument above, r a c e m i z a t i o n i s o c c u r r i n g on the same s i t e s as the cyclohexene r e d u c t i o n . The temporary p o i s o n i n g e f f e c t of oxygen on the racemiza-t i o n can a l s o be understood i n terms of Scheme 8. I f the 0 100 200 300 time (min) F i g u r e 26. . E f f e c t of Cyclohexane on the F i r s t Order K i n e t i c P l o t f o r the Platinum C a t a l y z e d Racemization of B i n a p h t h y l . t—1 CO 119 chemisorption of oxygen on the r e d u c t i o n s i t e s i s so strong that b i n a p h t h y l cannot compete for the s i t e s , then the c a t a l y z e d r e a c t i o n w i l l be stopped as long as the oxygen remains on the s u r f a c e . However, i f the d e s o r p t i o n of the r e d u c t i o n product, water, i s e s s e n t i a l l y i r r e v e r s i b l e , then once the r e d u c t i o n i s complete the p o i s o n i n g e f f e c t i s stopped. At t h i s p o i n t i t was decided to determine through which stage of the r e d u c t i o n the adsorbed b i n a p h t h y l proceeded. In other words, does r a c e m i z a t i o n proceed through step (2) or step (3) i n Scheme 8? I f the adsorbed b i n a p h t h y l a c t u a l l y added a hydrogen atom in a r e v e r s i b l e step (step 3), then some hydrogen-deuterium exchange with the b i n a p h t h y l molecule would be ex-pected i f the platinum oxide were reduced i n deuterium to pro-duce a metal s u r f a c e covered with deuterium r a t h e r than hydrogen. U n f o r t u n a t e l y , before these experiments could be c a r r i e d out the c a t a l y s t underwent an u n e x p l a i n a b l e l o s s i n a c t i v i t y . T h i s l o s s , and attempts to regenerate the higher a c t i v i t y c a t a l y s t , are d i s c u s s e d i n the f o l l o w i n g s e c t i o n . E. THE LOSS IN CATALYTIC ACTIVITY At one p o i n t during t h i s work no platinum c a t a l y z e d r e -a c t i o n s were run f o r a p e r i o d of about four weeks. Before t h i s p e r i o d , f i r s t order r a t e constants were on the order of 6.1 x 10~ 3 (min - 1) f o r a 1.0 x 10~ 3 M s o l u t i o n of b i n a p h t h y l at 25.0°. A l s o , every batch of reduced platinum oxide had been a c t i v e . When work resumed,: f i r s t order r a t e constants were t y p i c a l l y 120 3.0 x 10 J (min x ) . P o i n t s on the f i r s t order p l o t s were a l s o much more s c a t t e r e d , or showed some d e a c t i v a t i o n before one h a l f l i f e had e x p i r e d . Some batches of c a t a l y s t were not a c t i v e at a l l . The reason f o r t h i s l o s s i n a c t i v i t y i s not at a l l c l e a r . The reagents used f o r a l l r e a c t i o n s were i d e n t i c a l . Neverthe-l e s s , attempts were made to l o c a t e and c o r r e c t the source of the problem. The e t h a n o l , p r e v i o u s l y used as s u p p l i e d , was d r i e d and d i s t i l l e d . A l l glassware was cleaned with chromic a c i d , concentrated a l c o h o l i c potassium hydroxide, acetone, and d r i e d in an oven. The hydrogenation apparatus was a l s o c l e a n e d . The hydrogen, i n a d d i t i o n to being deoxygenated and d r i e d , was passed through a l i q u i d n i t r o g e n t r a p to remove p o s s i b l e hydrocarbon contaminants. None of these cleanup procedures had a s i g n i f i -cant e f f e c t on c a t a l y s t a c t i v i t y . I t had been d i s c o v e r e d e a r l i -er that even platinum oxide which was years o l d would s t i l l pro-duce an a c t i v e c a t a l y s t , so the platinum oxide d i d not appear to be the problem. D i f f e r e n t methods of s t i r r i n g were a l s o t r i e d with no success i n improving c a t a l y s i s . Running the c a t a l y s t through s e v e r a l o x i d a t i o n - r e d u c t i o n c y c l e s using hydrogen per-oxide as oxidant (and hydrogen as reductant) d i d not improve c a t a l y s i s . Because the c a t a l y s t had l o s t i t s r e p r o d u c i b i l i t y and r e -l i a b i l i t y , continued s t u d i e s i n t o the mechanism of the platinum c a t a l y z e d r e a c t i o n were abandoned. T h i s i s unfortunate s i n c e the hydrogen-deuterium exchange experiment may have r e v e a l e d 121 more f e a t u r e s of the c a t a l y z e d r a c e m i z a t i o n . Future s t u d i e s might determine the extent and nature of involvement of other t r a n s i t i o n metal c a t a l y s t s i n the b i n a p h t h y l r a c e m i z a t i o n . I t i s p o s s i b l e that the p e c u l i a r k i n e t i c e f f e c t - that the c a t a -l y z e d r a t e i s independent of the c o n c e n t r a t i o n of the c a t a l y s t -seen i n the platinum c a t a l y z e d r e a c t i o n i s a g e n e r a l f e a t u r e of the c a t a l y z e d r a c e m i z a t i o n of b i n a p h t h y l by t r a n s i t i o n metal c a t a l y s t s . Other metals or other forms of platinum may be more amenable to study than was Adams' C a t a l y s t . F. CONCLUSION Reduced platinum oxide (Adams' C a t a l y s t ) has been shown to c a t a l y z e the ra c e m i z a t i o n of 1 , 1 1 - b i n a p h t h y l i n e t h a n o l . As i n the case with the carbon and Raney N i c k e l c a t a l y z e d racemiza-t i o n s (Chapters II and III) , the platinum c a t a l y z e d r e a c t i o n f o l l o w s simple f i r s t order k i n e t i c s . There i s no d e t e c t a b l e a d s o r p t i o n or i n t e r f e r i n g r e d u c t i o n d u r i n g the r e a c t i o n . The c a t a l y s i s shows a p e c u l i a r k i n e t i c e f f e c t i n that the r e a c t i o n r a t e i s independent of the c o n c e n t r a t i o n of the c a t a -l y s t . U n l i k e other types of c a t a l y z e d r e a c t i o n s which are i n -dependent of the c o n c e n t r a t i o n of the c a t a l y s t , t h i s r e a c t i o n does not appa r e n t l y i n v o l v e any gas d i f f u s i o n p r o c e s s e s . An ex p l a n a t i o n f o r t h i s behaviour could not be found, n e i t h e r with an extended k i n e t i c treatment nor by the occurrence of a s o l u b l e c a t a l y s t which might have s a t u r a t e d the s o l u t i o n . 122 The presence of oxygen i n the r e a c t i o n s o l u t i o n t e m p o r a r i l y poisons the r e a c t i o n , a p p a r e n t l y f o r the d u r a t i o n of i t s reduc-t i o n to water. Cyclohexane and cyclohexene (which i s reduced to cyclohexane) show a permanent i n h i b i t o r y e f f e c t which i n -creases with the c o n c e n t r a t i o n of the compound. These r e s u l t s were i n t e r p r e t e d as i n d i c a t i n g t h at the r e d u c t i o n and racemiza-t i o n s i t e s were the same. Continued s t u d i e s , which would have i n v o l v e d hydrogen-deuterium exchange experiments, were not pos-s i b l e because of an u n c o n t r o l l a b l e decrease i n c a t a l y s t a c t i v i t y . Since both n i c k e l and platinum c a t a l y z e the r a c e m i z a t i o n of b i n a p h t h y l , other t r a n s i t i o n metals may a l s o be s u i t a b l e c a t a -l y s t s . I f they proved amenable to study, then a comparison might be made of the f e a t u r e s of the d i f f e r e n t c a t a l y z e d r a c e -m i z a t i o n s . The n i c k e l and platinum r e a c t i o n s a l r e a d y d i f f e r i n one r e s p e c t : while the r e d u c t i o n and r a c e m i z a t i o n s i t e s on n i c k e l are independent of one another, they appear to be the same on platinum. On the other hand, s i n c e no extended k i n e t i c a n a l y s i s was p o s s i b l e with n i c k e l , i t i s not known whether i t (or other t r a n s i t i o n metals) show c a t a l y z e d r a c e m i z a t i o n r a t e s which are independent of c a t a l y s t c o n c e n t r a t i o n . Features such as these might be b e t t e r c l a r i f i e d by s t u d i e s with a more r e -l i a b l e c a t a l y s t . 123 V. EXPERIMENTAL A. GENERAL Bi n a p h t h y l was s y n t h e s i z e d a c c o r d i n g to the method of 19 S a k e l l a r i o s and Kyrimis and r e s o l v e d by the s o l i d s t a t e 20 method of Pincock and Wilson . Solvents f o r s y n t h e s i s were reagent grade unless otherwise i n d i c a t e d . S o l v e n t s f o r k i -n e t i c and a d s o r p t i o n s t u d i e s were spectrograde with the f o l -lowing e x c e p t i o n s : hexane and heptane were reagent grade, 100% ethanol was used as r e c e i v e d from s u p p l i e r and acetone was reagent grade and d i s t i l l e d from potassium permanganate Gases were reagent grade and deoxygenated by bubbling through a s o l u t i o n of chromous c h l o r i d e f o l l o w e d by d r y i n g through a column of c a l c i u m s u l p h a t e . I n f r a r e d s p e c t r a were recorded on a P e r k i n Elmer 137 I n f r a r e d Spectrophotometer c a l i b r a t e d with the 1601 cm-''" band of p o l y s t y r e n e . S o l i d samples f o r i n f r a r e d s p e c t r a were pr e -pared as n u j o l mulls between sodium c h l o r i d e p l a t e s . S o l u t i o n samples were prepared i n CHC^ and s p e c t r a determined i n 0.506 mm sodium c h l o r i d e c e l l s . Band p o s i t i o n s are r e p o r t e d i n wavenumbers (cm "*") . Proton n u c l e a r magnetic resonance s p e c t r a were recorded on e i t h e r a V a r i a n HA-100 or a Bruker 270 or 400 MHZ FT spec-trometer. Samples were prepared as 10 to 15% s o l u t i o n s i n deuterochloroform or d ^ - d i m e t h y l - s u l f o x i d e . Chemical s h i f t s 124 are reported i n p a r t s per m i l l i o n r e l a t i v e to i n t e r n a l t e t r a -m e t h y l s i l a n e at 6 = 0.0. A l l s p e c t r a were recorded by s t a f f members of the NMR l a b o r a t o r y , the U n i v e r s i t y of B r i t i s h Columbia. Mass s p e c t r a were recorded on an A t l a s CH-46 spectrometer at an i o n i z i n g p o t e n t i a l of 70 eV by members of the U n i v e r s i t y of B r i t i s h Columbia Regional Mass Spectrometer F a c i l i t y . E l e -mental m i c r o a n a l y s i s were performed by Mr. Peter Borda, U n i -v e r s i t y of B r i t i s h Columbia. M e l t i n g p o i n t s were determined with a Thomas Unimelt C a p i l l a r y M e l t i n g P o i n t Apparatus using open tube c a p i l l a r i e s and are c o r r e c t e d . G a s - l i q u i d chroma-tography (glc) was performed using a Hewlett Packard 5830A Gas Chromatograph equipped with a flame i o n i z a t i o n d e t e c t o r and using n i t r o g e n as c a r r i e r gas with a 6 1 by 0.125" s t a i n l e s s s t e e l column packed with 3% OV-17 on Chromosorb W AW-DMCS, 80/100 mesh. O p t i c a l r o t a t i o n s were determined on e i t h e r a P e r k i n Elmer 141 or 241 MC Pol a r i m e t e r using a 1 dc or 1 cm q u a r t z - f a c e d OP jacketed c e l l . S p e c i f i c r o t a t i o n s ( [jsj ^ ) were c a l c u l a t e d using the equation I i°C a 1— aJ X le n g t h of c e l l (dc) x c o n c e n t r a t i o n (g/mil) A l l r a t e constants were determined from a l e a s t squares program g r a t e f u l l y provided by Dr. James Farmer, U n i v e r s i t y of B r i t i s h Columbia. E r r o r s are reported as average standard d e v i a t i o n s from the reported v a l u e s . 125 Changes i n the c o n c e n t r a t i o n o f compounds i n s o l u t i o n were measured by the method o f i n t e r n a l s t a n d a r d s . A f r e s h s o l u -t i o n o f 4 , 4 ' - d i m e t h y l - 1 , 1 1 - b i n a p h t h y l (DMB) was made up a t a c o n c e n t r a t i o n a p p r o x i m a t e l y e q u a l t o the i n i t i a l c o n c e n t r a t i o n o f the compound i n q u e s t i o n . DMB has a flame i o n i z a t i o n r e -sponse time s u f f i c i e n t l y d i f f e r e n t t o p e r m i t r e s o l u t i o n o f the response peaks. F i l t e r e d r e a c t i o n s o l u t i o n s were mixed 1:1 w i t h 100 u £ o f the DMB s o l u t i o n u s i n g a 100 yil Eppendorf p i p e t t e . F o l l o w i n g , g l c a n a l y s i s , r e l a t i v e c o n c e n t r a t i o n changes were de t e r m i n e d as changes i n the r a t i o o f peak a r e a o f the compound t o DMB peak a r e a . B. SYNTHESIS OF OPTICALLY ACTIVE SUBSTITUTED BINAPHTHYLS 1. 4,4'-Dibromo-1,1'-binaphthyl (DBB) R e s o l u t i o n s o f DBB were c i r c u m v e n t e d by p e r f o r m i n g the s y n t h e s i s on o p t i c a l l y a c t i v e b i n a p h t h y l . O p t i c a l l y a c t i v e b i n a p h t h y l (0.25 g, 1.0 mmole, \~o~] 23 = +191) was s t i r r e d i n 5 8 9 8 mil CHC1 3 c o o l e d i n an i c e bath a t 0 °C. B r 2 (0.25 mil, 4.7 mmole) was s y r i n g e d i n t o the s t i r r e d s o l u t i o n and the r e a c t i o n f o l l o w e d by g l c (270 °C). A f t e r the f i r s t new peak had com-p l e t e l y d i s a p p e a r e d and a second new peak appeared (40 m i n ) , the r e a c t i o n was quenched by the a d d i t i o n o f 10 mil s a t u r a t e d NaHS0 3. A f t e r removing the aqueous phase the s o l u t i o n was r i n s e d w i t h 10 mil s a t u r a t e d NaHS0 3, t w i c e w i t h 10 mil 10% NaOH, t w i c e w i t h 10 mil H 20, once w i t h s a t u r a t e d N a C l , and d r i e d over MgS0 4. The r e d s o l u t i o n was e v a p o r a t e d _in vacuo t o g i v e l i g h t 126 brown c r y s t a l s . These were d i s s o l v e d i n 25 nu CH 2C1 2, t r e a t e d once w i t h 50 mg d e c o l o r i z i n g N o r i t , and washed down a 1" by V alumina (Baker A n alyzed) column. The s o l v e n t was removed i n  vacuo to g i v e 0.34 g (82%) o f a f i n e w h i t e powder: mp 215.0 -go 217.0 T l i t mp 217.5, racemic I ; ("ofl 23 = +47 (9 . 1 mg/m£ i n —1 ^ J 5 8 9 CHC1 3); i r (CHClg) 1600, 1560 (1,2,3,4 s u b s t i t u t i o n ) ; mass spectrum p a r e n t peak m/e 414; A n a l . C a l c u l a t e d f o r C 2 o H 1 2 B r 2 : C, 58.29; H, 2.94; B r , 38.78. Found: C, 58.46; H, 2.90; B r , 38 .66 . 2. 4 , 4 ' - D i n i t r o - 1 , 1 ' - b i n a p h t h y l (DNB) R e s o l u t i o n s o f DNB were c i r c u m v e n t e d by n i t r a t i n g o p t i -c a l l y a c t i v e b i n a p h t h y l . In o r d e r t o f o l l o w the s y n t h e s i s o f DNB by t h i n l a y e r chromatography ( t i c ; Eastman Chromagram 13181 S i l i c a G e l w i t h F l u o r e s c e n t I n d i c a t o r No. 6060. C C l ^ as e l u a n t ) , a sample o f racemic DNB was o b t a i n e d u s i n g the method o f 81 S c h o e p f l e . DNB i n the r e a c t i o n m i x t u r e c o u l d be i d e n t i f i e d by comparing Rf v a l u e s w i t h the racemic compound (Rf = 0.30). B i n a p h t h y l (1.8 g, 7.1 mmole, ["of] 2 3 = -174 ) was d i s -' 5 8 9 s o l v e d i n 72 mil C C l ^ and c o o l e d i n an i c e bath a t 0 °C. Con-c e n t r a t e d H 2 S 0 4 (7.6 ml) was added w i t h r a p i d s t i r r i n g , f o l -lowed by 4.5 g (71 mmole) c o n c e n t r a t e d HNO^. A f t e r 15 min the o r g a n i c l a y e r was decanted and washed w i t h s a t u r a t e d NaHCO^ u n t i l s l i g h t l y b a s i c , then w i t h water u n t i l n e u t r a l , and f i -n a l l y w i t h s a t u r a t e d NaCl b e f o r e d r y i n g over MgSO^. Removal of the s o l v e n t _in vacuo gave 1.8 g o f a y e l l o w v i s c o u s o i l c o n s i s t i n g o f m o s t l y m ononitro compound ( v i a t i c ) . T h i s o i l 127 was d i s s o l v e d i n 42 mil a c e t i c a c i d , f o l l o w e d by the a d d i t i o n o f 18 mil 0.66 M HN0 3 and 90 mil 3.3 M H2SC>4. A f t e r s t i r r i n g f o r 1 hr the r e a c t i o n was judged complete by t i c and quenched by the a d d i t i o n o f 5 g i c e . The l i g h t y e l l o w c r y s t a l s which p r e c i p i -t a t e d were r i n s e d w i t h 100 m£ s a t u r a t e d NaHCO^, 100 mil H 20, 10 mil e t h a n o l , and d r i e d _in vacuo t o g i v e 2.1 g o f l i g h t y e l l o w powder. T h i s powder was mixed w i t h 6 g alu m i n a (Baker Analyzed) and packed i n t o a 30" by 2" d r y alumina column. E l u t i o n was begun w i t h 20% benzene/petroleum e t h e r (30-60°) and two y e l l o w bands appeared. The second y e l l o w band began coming o f f a f t e r 1 I and was c o l l e c t e d i n another 1 £ o f e l u a n t . T h i s f r a c t i o n was t r e a t e d w i t h d e c o l o r i z i n g N o r i t and q u i c k l y f i l t e r e d t o p r e -v e n t complete c a t a l y z e d r a c e m i z a t i o n . A f t e r another such t r e a t -ment the s o l v e n t was removed i r i vacuo t o g i v e 0.60 g (34%) o f 81 f i n e y e l l o w powder: mp 225 - 233 [~_ l i t . mp 246 , r a c e m i c ] ; FoT]23 = -11 (5.0 mg/mil i n C H C l ^ ) ; i r (CHC1 Q) 1550, 1360 (-N=0) , 888(-C-N), and 890, 845 (1,2,3,4 s u b s t i t u t i o n ) ; mass spectrum p a r e n t peak m/e 344; A n a l . C a l c u l a t e d f o r C 2 0 H 1 2 N 2 ° 4 : C, 69.77; H, 3.51; N, 8.14; 0, 18.59. Found: C, 69.66; H, 3.48; N, 8.03; 0, 18.83. 3. 4 , 4 ' - D i m e t h y l - 1 , 1 ' - b i n a p h t h y l (DMB) T h i s compound was a generous g i f t from Dr. Fu Ning Fung and was r e s o l v e d as d e s c r i b e d below w i t h o u t f u r t h e r p u r i f i c a -t i o n . 128 Racemic DMB was r e s o l v e d i n the f o l l o w i n g manner. A s i n g l e  c r y s t a l of naphthidine (approximately 2 mg) was added to a c l e a n , dry 1 ml ampule c o n t a i n i n g between 2 and 20 mg of pure, racemic DMB. The ampule was s e a l e d and immersed i n a 151 °C o i l bath f o r 4 min d u r i n g which time the DMB, but not the n a p h t h i d i n e , melted. The ampule was then q u i c k l y and smoothly t r a n s f e r r e d to a 100 °C o i l bath where the DMB was allowed to c r y s t a l l i z e on the naphthidine seed ( s e v e r a l hours to s e v e r a l days) to give a l a r g e opaque c r y s t a l . T h i s was repeated with 60 ampules, each being seeded with a d i f f e r e n t naphthidine c r y s t a l . P o l a r i m e t r i c a n a l y s i s of the ampule contents showed Fa"] 2 3 i n acetone ranging from + or - 31 to + or r 157 f o r the 1 ' 5 8 9 60 d i f f e r e n t ampules. The contents of ampules g i v i n g the same s i g n a value were combined to give two batches of brown c r y s t a l s , 0.26 g and 1.18 g. These were each mixed with equal weight alumina (Baker Analyzed) and each placed on top of a 1" by V dry alumina column. E l u t i o n with 600 mil 2-4% benzene/petroleum ether ( 3 0 - 6 0 ° ) gave white c r y s t a l s : 0.08 g, Fa~\ 2 9 = -95 (3 . 7 mg/mil i n ace-1 ' 5 8 9 tone) and 0.89 g, FaT] 2 9 = +86 ( 5 . 9 mg/m£ i n acetone). ' ' 5 8 9 4. 4,4'-Diamino-1,1'-binaphthyl (naphthidine) Naphthidine was a generous g i f t from Dr. K e i t h R. Wilson and was r e s o l v e d as d e s c r i b e d below without f u r t h e r p u r i f i c a -t i o n . 129 The r e s o l u t i o n of naphthidine was achieved as d e s c r i b e d by forming the (+)-(+) s a l t with (+) ammonium-a-bromo-D-camphor-n-sulphonate and then l i b e r a t i n g the (+)-naphthidine by t r e a t -ment of the s a l t with d i l u t e NH^OH. Naphthidine (1.5 g, 5.3 mmole) was d i s s o l v e d i n 35 mil hot acetone and poured i n t o 200 mil 0.29% HC1. The s o l u t i o n was s t i r r e d and 3.5 g (11 mmole) (+) ammonium-a-bromo-D-camphor-n-sulphonate ( A l d r i c h ) added. A f t e r 2 min l i g h t brown c r y s t a l s p r e c i p i t a t e d which were f i l t e r e d and r e c r y s t a l l i z e d from 35 mil 60% ethanol/H 20 to give 3.2 g f i n e l i g h t powder. Naphthidine was regenerated from the s a l t as needed. T y p i c a l l y , 0.82 g of the s a l t was suspended i n 13 mil e t h a n o l and the suspension degassed by bubbling N 2 through i t f o r h hr. Degassed 1.4% NH^OH (5 mil) was added slowly over 5 min. The s a l t d i s s o l v e d and naphthidine was p r e c i p i t a t e d as s l i g h t l y o f f white-powder by the a d d i t i o n of 5 mil c o l d , degassed H 20. The c r y s t a l s were f i l t e r e d and d r i e d _in vacuo. J u s t p r i o r to a k i n e t i c run the naphthidine was t r e a t e d with one-quarter i t s weight d e c o l o r i z i n g N o r i t , f i l t e r e d , and d r i e d iri vacuo. F a i l -ure to t r e a t the naphthidine with N o r i t gave e r r a t i c k i n e t i c s , even f o r the uncatalyzed r e a c t i o n . C. MODIFICATION OF CARBON 1. HNO3 o x i d a t i o n of N o r i t SGI N o r i t SGI (1 g, Matheson, Coleman and B e l l ) was r e f l u x e d f o r 4 hr i n 10 mil HNO-, (sp gr = 1.42, bp = 83 °C) . The HNO^ 130 was then d i s t i l l e d o f f u s i n g reduced a s p i r a t o r p r e s s u r e (20 mm). The N o r i t was c l e a n e d f u r t h e r by ten washings w i t h 20 m£ 0.1% NaOH. A f t e r each washing the N o r i t was c e n t r i f u g e d and the c e n t r i f u g a t e d e c a n t e d . The f i n a l c e n t r i f u g a t e was c l e a r . The c h a r c o a l was then r e f l u x e d o v e r n i g h t i n 0.1% HC1, c e n t r i f u g e d , r i n s e d w i t h P^O u n t i l n e u t r a l , and d r i e d o v e r n i g h t a t 100 °C i n a h i g h vacuum. 2. L i t h i u m aluminum h y d r i d e (LAH) r e d u c t i o n of Spheron 6 Spheron 6 (1 g, Cabot C o r p o r a t i o n ) was s t i r r e d a t room temperature w i t h 20 m£ t e t r a h y d r o f u r a n ( f r e s h l y d i s t i l l e d from LAH) under a d r y atmosphere. LAH (1.1 g, A l f a P r o d u c t s ) was added over 5 min. A m i l d r e a c t i o n o c c u r r e d w i t h the a d d i t i o n o f the LAH. The r e a c t i o n was r e f l u x e d f o r 10h hr a f t e r which time i t 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 . A p p r o x i m a t e l y 10 g i c e was added and the c l e a r l i q u i d phase d i s c a r d e d . The carbon was then t r e a t e d f o r 14 hr i n 75 m£ o f r e f l u x i n g 6 M H C l , then r i n s e d n e u t r a l w i t h 250 ml H2O, and d r i e d o v e r n i g h t i n a h i g h vacuum a t 82 °C. A b l a n k was p r e p a r e d by t r e a t i n g 1 gram of Spheron 6 i n an i d e n t i c a l f a s h i o n but w i t h o u t the a d d i t i o n o f any LAH. 3. L i t h i u m aluminum h y d r i d e r e d u c t i o n o f c h l o r i n a t e d  and brominated Spheron 6 These were reduced i n a manner i d e n t i c a l t o t h a t f o r the nonhalogenated Spheron 6. 131 4. C h l o r i n a t i o n o f Spheron 6 a t 450 ° C 2 7 Spheron 6 (Cabot C o r p o r a t i o n ) used f o r c h l o r i n a t i o n was f i r s t washed i n the f o l l o w i n g manner. Spheron 6 (10 g) was r e f l u x e d f o r 12 hr i n 6 M HC1 and s u b s e q u e n t l y r i n s e d t o neu-t r a l i t y w i t h H2O. I t was then e x t r a c t e d w i t h benzene f o r 20 hr on a S o x h l e t e x t r a c t o r and d r i e d f o r 20 hr on a h i g h vacuum d r y i n g p i s t o l a t 100 °C. Clean e d Spheron 6 (0.30 g) was spread over 10 cm i n the c e n t e r o f a 75 cm Pyrex tube f i t t e d w i t h a gas i n l e t and o u t - • l e t . The i n l e t was connected t o a tank o f Matheson, Coleman and B e l l r e a gent grade c h l o r i n e and the o u t l e t t o a s e r i e s o f two t r a p s , each c o n t a i n i n g 200 ml 20% NaOH. The Pyrex tube was p l a c e d i n t o a tube f u r n a c e and purged w i t h argon as i t came t o 450 °C (2 h r ) . C h l o r i n e was then bubbled through the system f o r 3 h r . A f t e r t h i s time the c h l o r i n e was t u r n e d o f f and the system c o o l e d to room tem p e r a t u r e . A i r was passed through the tube to evacuate any c h l o r i n e and then the carbon was r i n s e d i n t o a beaker and s t i r r e d w i t h 100 ml J^O f o r h h r . I t was then c e n t r i f u g e d and d r i e d on a h i g h vacuum d r y i n g p i s t o l f o r 12 hr a t 100 °C. A blank was p r e p a r e d by t r e a t i n g 0.30 g Spheron 6 i n an i d e n t i c a l manner but w i t h o u t the i n t r o d u c t i o n o f any c h l o r i n e i n t o the system. 28 5. B r o m i n a t i o n o f Spheron 6 Spheron 6 (1.0 g, Cabot C o r p o r a t i o n , c l e a n e d and degassed as f o r the c h l o r i n a t i o n b lank) was s t i r r e d f o r 24 hr i n 100 ml 132 of 0.1 N Br.> with 0.2 N KBr i n d i s t i l l e d H 20. The suspension was then c o o l e d , c e n t r i f u g e d , the red c e n t r i f u g a t e decanted, and the carbon obtained washed with 300 mil H 20 u n t i l a c l e a r c e n t r i f u g a t e was o b t a i n e d . The carbon was then d r i e d f o r 12 hr on a high vacuum d r y i n g p i s t o l at 100 °C. D. KINETICS OF THE UNCATALYZED AND CARBON CATALYZED REACTIONS K i n e t i c runs f o r the carbon c a t a l y z e d r e a c t i o n s were per-17 formed as p r e v i o u s l y d e s c r i b e d . In a t y p i c a l run, 20-30 mil of the c o r r e c t m o l a r i t y s o l u t i o n was e q u i l i b r a t e d f o r 15-30 min at the temperature of the run. A two-neck f l a s k f i t t e d with an overhead Corning V i b r a s t i r and c o n t a i n i n g a preweighed amount of the c a t a l y s t was a l s o e q u i l i b r a t e d at the d e s i r e d tempera-t u r e . The b i n a p h t h y l s o l u t i o n was p i p e t t e d i n t o the r e a c t i o n f l a s k and when h a l f had been added the V i b r a s t i r and timer were s t a r t e d . Approximately 1 mil samples were removed p e r i -o d i c a l l y with a Pasteur p i p e t t e and f i l t e r e d through a Swinny syr i n g e f i l t e r . P o l a r i m e t r i c a n a l y s i s was performed at X - 589 nm f o r b i n a p h t h y l , DBB, and DMB as s u b s t r a t e s . For naphthidine and DNB, s u f f i c i e n t l y high r o t a t i o n s c o u l d be obtained only i f A = 546 nm were used f o r a n a l y s i s . For the uncatalyzed r e a c t i o n s , s o l u t i o n s of the compounds were e q u i l i b r a t e d at the d e s i r e d temperature f o r 15 to 30 min. Samples were then p e r i o d i c a l l y removed and analyzed as f o r the c a t a l y z e d r e a c t i o n s . 133 F i r s t o r d e r p l o t s were o b t a i n e d by p l o t t i n g l n (a/a ) + 2 a g a i n s t t i m e . a i s the s o l u t i o n r o t a t i o n a t some time t and i s the s o l u t i o n r o t a t i o n a t t = 0. These p l o t s gave s t r a i g h t l i n e s f o r a l l the c a t a l y z e d and u n c a t a l y z e d r e a c t i o n s . E. SOLVATED ELECTRON CATALYZED RACEMIZATION OF 1,1 1-BINAPHTHYL Hexamethyl phosphoramide (HMPA) was heated over barium o x i d e f o r 3h hr a t 65 °C and then vacuum d i s t i l l e d (bp = 6 4 ° (0 . 6 5 mm)). I t was then degassed by the f r e e z e - t h a w method (3 c y c l e s ) and used i m m e d i a t e l y . S o l u t i o n s o f s o l v a t e d e l e c t r o n s were p r e p a r e d a c c o r d i n g t o the f o l l o w i n g method and used i m m e d i a t e l y . In a t y p i c a l p r e -p a r a t i o n a p p r o x i m a t e l y 100 mg sodium ( B r i t i s h Drug House) was c u t from the c e n t e r of a 1 i n c h cube, r i n s e d i n pentane, and q u i c k l y t r a n s f e r r e d t o a c l e a n , d r y , and preweighed 25 mil two-neck f l a s k . The f l a s k had been f i t t e d w i t h a g l a s s s t o p p e r and rubber septum and c o n t a i n e d a magnetic s t i r b a r . The f l a s k was then evacuated f o r \ hr t o e v a p o r a t e the s o l v e n t from the sodium and reweighed t o g i v e 65 mg sodium. F r e s h l y degassed HMPA (4 mil) was s y r i n g e d i n t o the f l a s k and s t i r r i n g s t a r t e d . A f t e r 10 min the s o l u t i o n s took on a dark b l u e hue. I t was sometimes n e c e s s a r y t o p i e r c e the sodium s u r f a c e w i t h a s y r i n g e needle i n o r d e r t o i n i t i a t e d i s s o l u t i o n . A f t e r 30 min o f s t i r -r i n g the sodium had c o m p l e t e l y d i s s o l v e d and the dark b l u e s o l u t i o n was ready f o r use. 134 A dry 10 ml t e s t tube c o n t a i n i n g 19 mg (0.075 mmole) b i -naphthyl was sealed with a rubber septum and purged with n i -trogen. F r e s h l y degassed HMPA (3 ml) was added to d i s s o l v e the b i n a p h t h y l , followed by 20 \xl of the solvated e l e c t r o n s o l u -t i o n . Under a stream of nitrogen some of the f a i n t yellow s o l u t i o n was syringed i n t o a 1 cm polarimeter c e l l and the decrease i n a was followed at room temperature (23.5 to 24.0 3 6 5 °C) by p e r i o d i c a l l y taking a polarimeter reading. At the end of a k i n e t i c run the o p t i c a l r o t a t i o n of the s o l u t i o n i n the t e s t tube was checked against the r o t a t i o n of the s o l u t i o n i n the c e l l . This confirmed that no d e a c t i v a t i o n or poisoning occurred when the s o l u t i o n was t r a n s f e r r e d to the c e l l . F. PREPARATION OF AND KINETICS WITH GRAPHITE INTERCALATES 1. Preparation and k i n e t i c s with potassium-graphite Potassium-graphite i n t e r c a l a t e s were prepared according 42 to the method of L a l a n c e t t e , et a l . A l l preparations used Fisher a c i d washed graphite and Matheson, Coleman and B e l l reagent grade potassium. In a t y p i c a l p r e p a r a t i o n , a 75 m£ three-neck pear-shaped f l a s k was f i t t e d w ith an overhead, screw type s t i r r e r and argon i n l e t . The system was flushed with argon and then flash e d dry with a Bunsen burner. Graphite (1.0 g, 83 mmole) was added to the f l a s k and the f l a s k was again flashed with a flame for 5 min. A piece of potassium was cut from the center of a 1 inch cube and r i n s e d i n pentane. Part of t h i s piece (0.15 g, 3.8 135 mmole) was added to the f l a s k i n approximately 50 mg p i e c e s . A f t e r the a d d i t i o n of each p i e c e the g r a p h i t e was heated with a Bunsen burner to melt the potassium. S h o r t l y a f t e r m e l t i n g , a b r i g h t orange CgK i n t e r c a l a t e formed which was d i s s i p a t e d when the g r a p h i t e was s t i r r e d . D i s s i p a t i o n was f a c i l i t a t e d by very r a p i d but c a r e f u l s t i r r i n g . A f t e r a l l the potassium had been added a 110-140 °C o i l bath was a p p l i e d and the s o l i d s t i r r e d f o r 1% hr. The r e s u l t -ing dark blue powder had the composition C22 K r a mixture of one 3 9 stage CgK and two stage C24K. K i n e t i c runs were performed immediately with a f r e s h batch of i n t e r c a l a t e . In a t y p i c a l run, a constant temperature bath was a p p l i e d to the f l a s k i n which 1.2 g of i n t e r c a l a t e had been prepared and the system was allowed % hr to come to thermal e q u i l i b r i u m . A s o l u t i o n of o p t i c a l l y a c t i v e b i n a p h t h y l ( Q * J = -132 , 30 ml 0.015 M i n d i s t i l l e d spectrograde n-heptane) was the r m a l l y e q u i l i b r a t e d f o r 15 to 30 min at the temperature of the run and then p i p e t t e d i n t o the r e a c t i o n f l a s k . The timer and s t i r r e r were s t a r t e d when h a l f the s o l u t i o n had been added. K i n e t i c s were f o l l o w e d as i n the carbon c a t a l y z e d r e a c t i o n s . A n a l y s i s was done at A. = 365 nm. 2. P r e p a r a t i o n of F e C l ^ - g r a p h i t e F e C l ^ - g r a p h i t e ( f i r s t stage, CgFeCl-j) was a generous g i f t from Dr. J . G. Hooley. I t had been prepared from spectrograde SP-1 g r a p h i t e (Union C a r b i d e ) . 136 Before u s i n g , the i n t e r c a l a t e was washed f r e e of adsorbed F e C l ^ i n the f o l l o w i n g manner. The i n t e r c a l a t e (3 g) was washed f i v e times with 25 mil acetone and then s t i r r e d f o r 3 hr - i n 100 mil acetone. I t was then f i l t e r e d and d r i e d i n vacuo f o r 3 hr. A l l f i l t r a t e s from the washings were yellow. T r e a t i n g F e C l ^ - g r a p h i t e with acetone i s known to remove 8 3 some of the i n t e r c a l a t e d F e C l 3 . Acetone has n e v e r t h e l e s s 84 been used by the same author to remove adsorbed F e C l 3 • 3. P r e p a r a t i o n of A l C l 3 - g r a p h i t e A l C l - j - g r a p h i t e ( f i r s t stage, CqAlCl^) was a generous g i f t from Dr. J.G. Hooley. I t had been prepared from spectrograde SP-1 g r a p h i t e (Union C a r b i d e ) . Before u s i n g , the i n t e r c a l a t e was washed f r e e of adsorbed A l C l ^ i n the f o l l o w i n g manner. The i n t e r c a l a t e (1 g) was washed three times with 20 mil 100% e t h a n o l and then s t i r r e d f o r lh hr i n 20 ml 100% e t h a n o l . The i n t e r c a l a t e was then f i l t e r e d and d r i e d in_ vacuo f o r 5 hr. The f i r s t washing pro-duced white smoke and heat, but subsequent ones d i d not. Since 8 5 h y d r o l y s i s of i n t e r c a l a t e d A l C l ^ i s p o s s i b l e , t h i s may have occurred d u r i n g the washing. 4. K i n e t i c s of the g r a p h i t e and i n t e r c a l a t e d g r a p h i t e  c a t a l y z e d r e a c t i o n s The k i n e t i c s of the g r a p h i t e and i n t e r c a l a t e d g r a p h i t e r e a c t i o n s were run i n the same manner. In a t y p i c a l example, 8 6 a 100 mJl three-neck Morton f l a s k was equipped with a F i s h e r 137 Dynamix s t i r r e r and n i t r o g e n i n l e t . I t was then charged with a known amount of c a t a l y s t , p l a c e d i n a constant temperature bath, and allowed 30 min to come to thermal e q u i l i b r i u m . A s o l u t i o n of o p t i c a l l y a c t i v e b i n a p h t h y l i n n-heptane was t h e r -mally e q u i l i b r a t e d f o r 15 to 30 min at the temperature of the run. I t s o p t i c a l a c t i v i t y was then determined and the s o l u -t i o n p i p e t t e d i n t o the r e a c t i o n f l a s k . The timer and s t i r r e r were s t a r t e d when h a l f the b i n a p h t h y l s o l u t i o n was added. K i n e t i c s were followed as i n the carbon c a t a l y z e d r e a c t i o n s . For the i n t e r c a l a t e c a t a l y z e d r e a c t i o n s i t was a l s o de-termined whether some s o l u b l e compounds were r e s p o n s i b l e f o r the c a t a l y s i s . At the end of a c a t a l y t i c run the c a t a l y s t was allowed to s e t t l e to the bottom of the f l a s k and approximately 2 mil of the supernatant was f i l t e r e d through a Swinny sy r i n g e _ 3 f i l t e r and mixed 1:1 with a 1.0 x 10 M s o l u t i o n of o p t i c a l l y a c t i v e b i n a p h t h y l . The o p t i c a l r o t a t i o n of the s o l u t i o n was the same before and a f t e r shaking the s o l u t i o n f o r 10 min. The a c t i v i t y of F e C l ^ and A l C l ^ towards b i n a p h t h y l race-m i z a t i o n in n-heptane was a l s o determined. In the case of _3 F e C l 3 , 2 mil of 1.0 x 10 M o p t i c a l l y a c t i v e b i n a p h t h y l was shaken f o r 10 min with 100 mg F e C l 3 (Fisher A n a l y t i c a l Reagent). There was no change in the o p t i c a l r o t a t i o n of the s o l u t i o n . In the case of A1C1 3, an i d e n t i c a l t e s t using 12 mg A1C1 3 ( B r i -t i s h Drug House, f r e s h l y sublimed) showed a 66% l o s s i n o p t i c a l a c t i v i t y and 24% l o s s i n b i n a p h t h y l . This i n d i c a t e d that 138 s o l i d AlCl-j i n n-heptane can both racemize and r e a c t with b i -naphthyl . When comparing c a t a l y s i s by an i n t e r c a l a t e with that by g r a p h i t e , the comparison was always made between the i n t e r -c a l a t e and the g r a p h i t e from which i t was made. Weights of i n t e r c a l a t e s were adjusted to account f o r t h e i r lower carbon content. Thus F e C l ^ - g r a p h i t e c o n t a i n s 31.8% carbon and so 1.0 g would be e q u i v a l e n t to 0.32 g of g r a p h i t e . G. PREPARATION AND USE OF RANEY NICKEL 48 1. P r e p a r a t i o n of Raney N i c k e l NaOH (20 g) was added to 75 mil d i s t i l l e d H 20 i n a 250 mil beaker. The s o l u t i o n was s t i r r e d with a magnetic s t i r r e r and maintained at 75 °C. N i - A l a l l o y powder (15 g, A l f a Inorganics) was added over 30 min. A vigorous r e a c t i o n ensued with each a d d i t i o n of a l l o y powder and the temperature was maintained between 70 °C and 90 °C by use of a c o l d water bath. A f t e r a l l the a l l o y had been added, the suspension was allowed to c o o l to room temperature with s t i r r i n g (45 min). The n i c k e l was allowed to s e t t l e out, the milky aqueous phase decanted, and the n i c k e l was r i n s e d to n e u t r a l i t y with d i s t i l l e d H^O (8 to 20 I). I t was then r i n s e d three times with 100 mil EtOH, three times with 100 mil n-heptane, and s t o r e d i n a sea l e d b o t t l e under n-heptane. Batches of Raney N i c k e l were used w i t h -i n s i x weeks of p r e p a r a t i o n . 139 Washing the c a t a l y s t w i t h tap water r a t h e r than d i s t i l l e d t^O p o i s o n e d the c a t a l y s t towards r e d u c t i o n and r a c e m i z a t i o n , but not towards a d s o r p t i o n . 2. C h a r a c t e r i z i n g batches o f Raney N i c k e l For each b a t c h o f Raney N i c k e l p r e p a r e d , i t had t o be de-termined f i r s t whether t h a t b a t c h of c a t a l y s t was a c t i v e towards r e d u c t i o n , r a c e m i z a t i o n , and a d s o r p t i o n and s e c o n d l y , what amount o f p o i s o n was n e c e s s a r y t o s t o p the i n d i v i d u a l p r o c e s s e s . In the former c a s e , 1.3 g o f f r e s h Raney N i c k e l s l u r r y ( t o t a l volume of 1 ml) was added t o a pear-shaped f l a s k f i t t e d w i t h a screw type s t i r r e r and n i t r o g e n i n l e t . T h i s was f o l l o w e d by 4 -3 — ml 5.0 x 10 M o p t i c a l l y a c t i v e b i n a p h t h y l (Fa I = -132). L - —1 5 8 9 S t i r r i n g was begun and 10 sec l a t e r the t = 0 sample removed w i t h a P a s t e u r p i p e t t e and f i l t e r e d through a Swinny s y r i n g e f i l t e r . The s o l u t i o n was a n a l y z e d f o r o p t i c a l a c t i v i t y and b i n a p h t h y l c o n c e n t r a t i o n . Other samples were removed p e r i o d i -c a l l y and a n a l y z e d i n a s i m i l a r f a s h i o n . G l c a n a l y s i s showed the appearance of r e d u c t i o n p r o d u c t s and a decrease i n b i n a p h -t h y l c o n c e n t r a t i o n . P o l a r i m e t r i c a n a l y s i s showed a decrease i n o p t i c a l a c t i v i t y . The amount of p o i s o n n e c e s s a r y t o p o i s o n the i n d i v i d u a l p r o c e s s e s was determined by t r i a l and e r r o r . The amount r e -q u i r e d was e x p r e s s e d i n one o f two ways, depending on how the Raney N i c k e l was measured. In one method the Raney N i c k e l s l u r r y was r a p i d l y s t i r r e d w i t h a magnetic s t i r r e r and measured 140 volumes removed with a wide mouth Pasteur p i p e t t e . In t h i s case the amount of poison was expressed i n mg poison/m£ s l u r r y . In the second method a measured volume of s l u r r y was weighed and the weight of Raney N i c k e l determined assuming the volume to be due e n t i r e l y to the s o l v e n t . Since none of the n i c k e l d i s s o l v e s i n the heptane, (density of n i c k e l ) ( v o l u m e of n i c k e l ) + ( d e n s i t y of heptane) (volume of heptane) = weight of s l u r r y The weight of the s l u r r y was always l e s s than 1.5 g per 1.0 mft t o t a l volume. Thus i f x = mi of heptane and t a k i n g the d e n s i t y of n i c k e l as 8.9 (g/m£) and the d e n s i t y of heptane as 0.68 (g/m£), then x > 0.90 mi The maximum e r r o r i n the weight of n i c k e l would thus be 0.07 g or 8%. Using t h i s method the amount of poison was expressed in mg poison/mg N i . In g e n e r a l e i t h e r d o d e c a n e t h i o l ( A l d r i c h ) or elemental s u l f u r (0.014 M i n n-heptane) c o u l d be used as a po i s o n . How-ever, at high c o n c e n t r a t i o n s the t h i o l turned the r e a c t i o n s o l u t i o n l i g h t brown and made p o l a r i m e t r i c readings d i f f i c u l t . For t h i s reason s u l f u r was used as poison whenever p o l a r i m e t r i c analyses were to be performed. 141 In a t y p i c a l c h a r a c t e r i z a t i o n , a 10 mil t e s t tube was charged with 0.78 g of Raney N i c k e l s l u r r y ( t o t a l volume = 1 mil, 0.10 g Raney N i c k e l ) . S u l f u r (4 mil, 0.014 M i n n-heptane) was added and the s o l u t i o n shaken f o r 2 min. Then, 4 mil of 3.9 x 10 M o p t i c a l l y a c t i v e b i n a p h t h y l (f~a I = -132) was 1 ' 5 8 9 added and, a f t e r two i n v e r s i o n s of the t e s t tube, the t = 0 sample was removed, f i l t e r e d , and analyzed as above. Shaking was continued f o r 20 min and another sample removed and ana-l y z e d to determine the e f f e c t of that amount of p o i s o n . S i m i -l a r experiments were repeated i n order to determine the e f f e c t of more or l e s s p o i s o n . 3. P o i s o n i n g of Raney N i c k e l f o r a k i n e t i c or a d s o r p t i o n  study In these cases the Raney N i c k e l was poisoned i n the f l a s k to be used f o r the study: e i t h e r a three-neck pear-shaped 8 6 f l a s k with a screw type s t i r r e r or a Morton f l a s k with an overhead bladed Dynamix s t i r r e r . A l l r e a c t i o n s were done under N 2 or Ar. The amount of poison used was determined by the c h a r a c t e r i z a t i o n experiments above. In a t y p i c a l a d s o r p t i o n study, 5.0 g Raney N i c k e l s l u r r y ( t o t a l volume = 4 mil) was r i n s e d i n t o a 100 mil Morton f l a s k ( f i t t e d with a bladed Dynamix s t i r r e r and n i t r o g e n i n l e t ) with 25 mil n-heptane. The suspension was e q u i l i b r a t e d at 7.5 °C for h hr. S t i r r i n g was s t a r t e d and 650 jail of 5.0 x 10 M 142 do d e c a n e t h i o l ( A l d r i c h ) i n n-heptane was added dropwise over 2 min. The poisoned c a t a l y s t was used immediately. Poison i n g the c a t a l y s t f o r a k i n e t i c run was done i n an i d e n t i c a l manner but using the a p p r o p r i a t e amount of poison r e q u i r e d to onl y stop the r e d u c t i o n r e a c t i o n . 4. K i n e t i c , a d s o r p t i o n , and product a n a l y s i s s t u d i e s These s t u d i e s were a l l performed i n a s i m i l a r manner, the only d i f f e r e n c e being the amount of poison used to poison the c a t a l y s t and the method of s o l u t i o n a n a l y s i s . In a t y p i c a l a d s o r p t i o n study, 75 ml 0.012 M b i n a p h t h y l was e q u i l i b r a t e d at 7.5 °C f o r h hr and then p i p e t t e d i n t o the r e a c t i o n f l a s k c o n t a i n i n g f r e s h l y poisoned c a t a l y s t . S t i r r i n g was s t a r t e d and a f t e r 10 sec the t = 0 reading removed and f i l t e r e d as d e s c r i b e d i n the C h a r a c t e r i z a t i o n s e c t i o n above. Q u a n t i t a t i v e a n a l y s i s was performed as d e s c r i b e d i n the General s e c t i o n . S i m i l a r a n a l y s i s was used i n the product d i s t r i b u t i o n s t u d i e s . In the k i n e t i c runs the f i l t e r e d s o l u t i o n s were ana-ly z e d f o r o p t i c a l a c t i v i t y . Sub-zero temperatures were achieved using s l u r r i e s of CHC1 or C C l ^ i n dry i c e . Determinations of the amount adsorbed v e r -sus temperature were made on the same batch of c a t a l y s t s by simply changing the constant temperature bath and a l l o w i n g the a d s o r p t i o n to come to e q u i l i b r i u m (2 to 6 hr as determined by g l c ) . 143 5. Synthesis of 5,6,7,8,5',6',7',8'-Octahydro-1,1'-binaphthyl Racemic b i n a p h t h y l (2.0 g, 7.9 mmole) was d i s s o l v e d i n 250 ma spectrograde n-heptane and s t i r r e d under N 2. Approximately 10 g Raney N i c k e l was added and the r e a c t i o n was s t i r r e d under r e f l u x f o r 2 weeks. During t h i s time the b i n a p h t h y l was c l e a n -l y reduced through three i n t e r m e d i a t e s ( v i a g l c , 190 °C) to give a f i n a l f o u r t h product. The s o l u t i o n was then f i l t e r e d , t r e a t e d once with d e c o l o r i z i n g N o r i t and evaporated to dryness to give a c l e a r o i l . A f t e r 1 hr i n an i c e bath, c r y s t a l s began to ap-pear and the o i l was placed i n the f r e e z e r o v e r n i g h t . The c l e a r o i l , QoQ 2 3 = -4 .83 (49 mg/mil i n heptane) was removed from the 3 6 5 chunky c l e a r prisms, [~a~\\ 2 3 = +1.05 (28 mg/mil i n heptane). - 1 3 6 5 The c r y s t a l s were r e c r y s t a l l i z e d once from 100% EtOH to g i v e 0.60 g (29%) c l e a r prisms: mp 91.0 - 91.5; roTI 2 3 = 0; i r 1 ' 3 6 5 (CHCl^) 2900 (C-H); nmr (see body of t e x t ) ; mass spectrum par-ent peak m/e 262; Anal-.- C a l c u l a t e d f o r C 20^22* ^' 91 • 5 5 7 8.45. Found: C, 91.40; H, 8.65. H. PREPARATION AND USE OF PLATINUM A l l platinum was prepared by the r e d u c t i o n of P t 0 2 (Adam's C a t a l y s t , Matheson, Coleman, and B e l l ) on a s l o p i n g m a n i f o l d 8 7 hydrogenation apparatus as d e s c r i b e d by Augustine. In a t y p i c a l experiment, a 25 mil two-neck round bottom f l a s k was f i t t e d with a rubber septum and charged with 21 mg P t 0 2 , 20 mil 100% e t h a n o l , and a one inch T e f l o n - c o a t e d magnetic s t i r bar. The f l a s k was p l a c e d on the hydrogenation apparatus and reduced 144 for 20 h r s . During the f i r s t 15 min the f i n e l y d i s p e r s e d c a t a -l y s t coagulates to form l a r g e r p a r t i c l e s . A f t e r extended r e -d u c t i o n the f i n e d i s p e r s i o n again appeared (see body of t e x t ) . -3 Hydrogen uptake was 1.4 x 10 moles. -3 To the reduced c a t a l y s t was added 5 mJ, of 4.2 x 10 M o p t i c a l l y a c t i v e b i n a p h t h y l (\~a~~] 2 3 = +145 ). S t i r r i n g was J 5 8 9 s t a r t e d and the t = 0 and subsequent samples removed by w i t h -drawing 1 ml a l i q u o t s of the r e a c t i o n suspension with a s y r i n g e f i t t e d with an 18 guage needle. The samples were then q u i c k l y f i l t e r e d through a Swinny s y r i n g e f i l t e r and analyzed f o r op-t i c a l a c t i v i t y . K i n e t i c data was t r e a t e d as f o r the carbon c a t a l y z e d r e a c t i o n s . To study the e f f e c t of platinum c o n c e n t r a t i o n on the r e -a c t i o n r a t e , one of two methods was used. In one case a k i n e t i c run was begun as above but a f t e r one h a l f l i f e the s t i r r i n g stopped and the c a t a l y s t allowed to s e t t l e to the bottom of the f l a s k . Some of the supernatant ( t y p i c a l l y one t h i r d ) was r e -moved and the s t i r r i n g s t a r t e d again at the new platinum concen-t r a t i o n . T h i s was termed the S t o p - S t a r t Method. In the second method a k i n e t i c run was a l s o s t a r t e d as above and followed f o r times between one and two h a l f l i v e s . A f t e r t h a t time the s t i r r i n g was stopped and a f r e s h volume of b i n a p h t h y l s o l u t i o n - of the same m o l a r i t y as the r e a c t i o n s o l u t i o n - was added. The r e a c t i o n was s t a r t e d again at the new platinum c o n c e n t r a t i o n . T h i s was termed the D i l u t i o n Method. 145 Both methods r e q u i r e d that one c l o s e l y determine the volume of samples removed i n order to a s c e r t a i n the change i n s o l u t i o n volume when the supernatant was removed or more s o l u -t i o n added. Both methods gave the same r e s u l t s i . e . the r a t e d i d not change with a change i n c a t a l y s t c o n c e n t r a t i o n . The dependence of r a t e on b i n a p h t h y l c o n c e n t r a t i o n was determined by using a v a r i a t i o n on the S t o p - S t a r t Method. A f -ter removing some of the supernatant an e q u i v a l e n t volume of a higher c o n c e n t r a t i o n b i n a p h t h y l s o l u t i o n was added and the s t i r r i n g r e s t a r t e d . In t h i s way the b i n a p h t h y l c o n c e n t r a t i o n , but not the c a t a l y s t c o n c e n t r a t i o n , was changed. A i r used f o r p o i s o n i n g was f i r s t f i l t e r e d through CaSO^ and then i n j e c t e d i n t o the r e a c t i o n s o l u t i o n over a p e r i o d of 20 sec. Cyclohexene (Matheson, Coleman, and B e l l ) was p u r i f i e d by washing three times with e q u i v a l e n t volumes of s a t u r a t e d NaHSO^ three times with d i s t i l l e d f^O, d r y i n g over MgSO^, and then d i s t i l l i n g under argon from CaH 2 (bp 82.5 °C, u n c o r r e c t e d ) . Cyclohexane ( F i s h e r , ACS C e r t i f i e d ) was p u r i f i e d by shak-ing four times with an e q u i v a l e n t volume of 1:1 H^SO^, HNO^, washing to n e u t r a l i t y with s a t u r a t e d NaHCO^, washing with d i s -t i l l e d H 20, d r y i n g over MgS0 4, and then d i s t i l l i n g (bp 79.8 °C, uncorrected) . Both cyclohexene and cyclohexane were added to the s t i r r e d r e a c t i o n suspension by slow i n j e c t i o n over a p e r i o d of 20 sec. Any other reagents added to the r e a c t i o n f l a s k were s y r i n g e d i n without f u r t h e r p u r i f i c a t i o n . 146 BIBLIOGRAPHY 1. Extended Abstracts, 13th Biennial Conference on Carbon, Irvine, C a l i f o r n i a , J u ly, 1977 2. R.W. Coughlin, Proc. Int. Congr. Catal., 4th, 2, 322 (1971) 3. D. Tobson, H. Harker, and W.F.K. Wynne-Jones, Surface Science, 9, 246 (1968) 4. P.H. Given and L.W. H i l l , Carbon, 6, 525 (1968) 5. J.A. Meier and L.W. H i l l , J. Cat., 32, 80 (1974) 6. G.C. 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