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UBC Theses and Dissertations

Solutions in difluorophosphoric acid Reed, William 1968

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SOLUTIONS IN DIFLUOROPHOSPHORIC ACID ' -by W i l l i a m Reed A THESIS SUBMITTED IN PARTIAL FULFILMENT OF -THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY i n the Department of Chemistry We accept t h i s t h e s i s as conforming to the re q u i r e d standard THE UNIVERSITY OF BRITISH COLUMBIA January 196S 0 W i l l i a m Reed 1968 In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f t h e r e q u i r e m e n t s f o r an a d v a n c e d d e g r e e a t t h e U n i v e r s i t y o f B r i t i s h C o l u m b i a , I a g r e e t h a t t h e L i b r a r y s h a l l m a k e i t f r e e l y a v a i l a b l e f o r r e f e r e n c e a n d s t u d y . I f u r t h e r a g r e e t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y p u r p o s e s may be g r a n t e d by t h e H e a d o f my D e p a r t m e n t o r by h i s r e p r e s e n -t a t i v e s . I t i s u n d e r s t o o d t h a t c o p y i n g o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l n o t be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . D e p a r t m e n t o f The U n i v e r s i t y o f B r i t i s h C o l u m b i a V a n c o u v e r 8, C a n a d a Date February 27, 1968 ( i i ) ABSTRACT -The p h y s i c a l and i n o r g a n i c chemistry of s o l u t i o n s i n di f l u o r o p h o s p h o r i c a c i d , HPO^Fg, has been s t u d i e d , as part of a general study of s o l u t i o n s i n non-aqueous pro t o n i c s o l v e n t s . D i f l u o r o p h o s p h o r i c a c i d i s a c o l o u r l e s s , a s s o c i a t e d l i q u i d which might be expected to have solvent p r o p e r t i e s s i m i l a r t o those of other p r o t o n i c systems such as H^O, I-^SO^ and HSO^F. However, e l e c t r i c a l c o n d u c t i v i t y s t u d i e s of s o l u t i o n s of various e l e c t r o l y t e s and nuclear magnetic resonance s t u d i e s of s o l u t i o n s of a l k a l i metal difluorophosphates i n d i c a t e that the a c i d i s a poor so l v e n t f o r e l e c t r o l y t e s and that i o n - p a i r i n g i s probably extensive. Acid-base behaviour i n HPO2F2 has been e x t e n s i v e l y i n -v e s t i g a t e d . Compounds which behave as bases i n t h i s system i n -clude metal di f l u o r o p h o s p h a t e s , c h l o r i d e s , n i t r a t e s and carbonates, organic amines, and some organic nitro-compounds and c a r b o x y l i c a c i d s . Inorganic molecules such as F^SO^, HSO^F and SbF^ behave as a c i d s . Reaction between an a c i d and a base i n HPO2F2 commonly r e s u l t i n the format i o n of an i n s o l u b l e s a l t . The r e a c t i o n between KPO2F2 and SbF^, f o r example, has been used t o prepare the new compound KSbF^P02F2« To f u r t h e r i n v e s t i g a t e the f a c t o r s a f f e c t i n g a c i d s t r e n g t h s , c r y o s c o p i c and e l e c t r i c a l c o n d u c t i v i t y s t u d i e s of va r i o u s i n o r g a n i c oxy-acids were c a r r i e d out i n nitrobenzene, as so l v e n t . The a c i d s H^SO^, HSO3F and HPO2F2 appeared'to be v i r -t u a l n o n - e l e c t r o l y t e s i n nitrobenzene, vrith ^SO^ apparently e x h i b i t i n g some p o l y m e r i z a t i o n . ( i i i ) TABLE OF CONTENTS • PAGE CHAPTER I General I n t r o d u c t i o n ' 1 1.1 P r o p e r t i e s of d i f l u o r o p h o s p h o r i c a c i d 1 1.2 Acid-base behaviour i n pro t o n i c s o l v e n t s 4 1.3 O u t l i n e of present work 6 CHAPTER I I S o l u t i o n s of Metal Difluorophosphates 8 2.1 I n t r o d u c t i o n 8 2.2 Experimental 8 A) P r e p a r a t i o n and p u r i f i c a t i o n of m a t e r i a l s 8 i d i f l u o r o p h o s p h o r i c a c i d i i metal difluorophosphates B) E l e c t r i c a l c o n d u c t i v i t y 10. C) Nuclear magnetic resonance 17 D) V i s c o s i t y 18 E) Density 19 2.3 R e s u l t s and d i s c u s s i o n 19 A) E l e c t r i c a l c o n d u c t i v i t y 19 B) Nuclear magnetic resonance 30 C) Density 41 D) V i s c o s i t y 1+6 CHAPTER I I I Miscellaneous Bases 48 - A) Organic s o l u t e s 48 3 .1 I n t r o d u c t i o n 48 3 . 2 Experimental 48 A) E l e c t r i c a l c o n d u c t i v i t y 48 B) P r e p a r a t i o n and p u r i f i c a t i o n of m a t e r i a l s 48 3.3 R e s u l t s and d i s c u s s i o n 49 (iv) • . PAGE B) Inorganic s o l u t e s . 53 3 . 4 I n t r o d u c t i o n 53 3 .5 Experimental 54 3-6 R e s u l t s and d i s c u s s i o n " 54 CHAPTER IV Acids and Acid-Base Reactions 62 4 . 1 I n t r o d u c t i o n 62 4 . 2 Experimental 63 A) P r e p a r a t i o n and p u r i f i c a t i o n of m a t e r i a l s 63 B) E l e c t r i c a l c o n d u c t i v i t y 64 C) Nuclear magnetic resonance 65 4 .3 P r o t o n i c a c i d s : r e s u l t s and d i s c u s s i o n 65 4 . 4 SbF^ s o l u t i o n s : r e s u l t s and d i s c u s s i o n 72 4 .5 Studies on K S b F 5 P 0 2 F 2 95 CHAPTER V Nitrobenzene. S o l u t i o n s 102 5.1 I n t r o d u c t i o n 102 5.2 Experimental 103 A) Cryoscopy 103 B) E l e c t r i c a l c o n d u c t i v i t y 108 C) P r e p a r a t i o n of m a t e r i a l s 109 5.3 R e s u l t s and d i s c u s s i o n 109 A) F l u o r o s u l p h u r i c a c i d s o l u t i o n s 110 B) Sulphuric a c i d s o l u t i o n s 117 C) P i f l u o r o p h o s p h o r i c a c i d s o l u t i o n s 121 5.4 Conclusion 121 CHAPTER VI Summary and Suggestions f o r Further Work 123 6.1 -Summary 123 6.2 Suggestions f o r f u r t h e r work 125 BIBLIOGRAPHY . 1 2 7 (v) LIST OF TABLES . • TABLE PAGE 1. P h y s i c a l P r o p e r t i e s of Difluorophosphoric A c i d t 2 2. S p e c i f i c C o n d u c t i v i t i e s of the A l k a l i and Some A l k a l i n e 20 Ea r t h M e t a l Difluorophosphates at 25° 3. Equivalent C o n d u c t i v i t i e s of Some Difluorophosphates at 25° . 23 4 . S p e c i f i c C o n d u c t i v i t i e s of Some Potassium S a l t s i n Various Solvents 26 5. 1H, 1 9 F and ^ 1P Chemical S h i f t s f o r S o l u t i o n s of MP0„F 9 i n HP0 2F 2 32 6. D e n s i t i e s and V i s c o s i t i e s of Some Solutes i n HP0 2F 2 at 25° 42 7. S p e c i f i c C o n d u c t i v i t i e s of Some Organic Bases i n KPOoFo at 25° . 50 • #. S p e c i f i c C o n d u c t i v i t i e s of Various E l e c t r o l y t e s i n HPO F at 25° 55 2 2 9. S p e c i f i c C o n d u c t i v i t i e s of Some Acids i n HP0 2F 2 at 25° 66 10. 19F.and 31p Ch emical S h i f t s and Coupling Constants f o r Some Complex Antimony-Fluorine Species 82 11. I n f r a r e d Spectra .of Various Inorganic F l u o r i n e Compounds 96 12. I n f r a r e d Snectrum of Gaseous Products from the Decomposition of K S b F 5 P 0 2 F 2 100 13. Cryoscopic Measurements i n Nitrobenzene 111 14. S p e c i f i c C o n d u c t i v i t i e s of Some E l e c t r o l y t e s i n Nitrobenzene at 25° 114 15. E q u i v a l e n t C o n d u c t i v i t i e s of Some E l e c t r o l y t e s i n Nitrobenzene at 25° 119 (vi) LIST OF FIGURES FIGURE PAGE 1. Difluorophosphoric Acid D i s t i l l a t i o n Apparatus 9 2. E l e c t r i c a l Conductivity Cell - 11 3 . Injector, used for Solute Additions to the Conductivity . Cell ' 13 4 . Microburette, used for Solute Additions to the Conductivity Cell 16 5. Specific Conductivities of Some Difluorophosphates at 2 5 ° 21 6. Equivalent Conductivities of Some Dif luorophosphates at 2 5 ° plotted against the Square Root of the Ionic Strength 25 7. N.M.R. Chemical Shifts for MP0 2F 2 i n HP0 2F 2 34 8. 1 9 F N.M.R. Chemical Shifts for MPOgFg i n HP0 2F 2 35 9 . 3 1P N.M.R. Chemical Shifts for MP0 2F 2 i n HP0 2F 2 36 10. Densities of Some Metal Difluorophosphates i n HPO^Fo 4 4 at 2 5 ° 11. Specific Conductivities o-f Some Organic Bases i n HP0 9F 9 at 25° 51 12. Specific Conductivities, of Various Electrolytes in HP0 2F 2 at 2 5 ° 56 1 3 - Specific Conductivities of Various Potassium Salts i n HP0 2F 2 at 2 5 ° 59 14. Specific Conductivities of Some Acids in HP0 2F 2 at 25° 08 15. Acid-Base Titrations i n HP0 2F 2 at 25° 70 16. - Acid-Base Titrations for SbF against KPO F i n HPO F at 2 5 ° 5 . 1 Z 1 75 17. 1 9 F N.M.R. Spectrum of a 3 . 6 3 molal SbF£./HP0oFo Solution at 30° 5 ^ d. 7 g 18. 1 9 F N.M.R. Spectrum of a 3 . 6 3 molal 3bF_/HP0oF Solution at - 6 5 ° 5 2 2 79 19. 1 9 F N.M.R. Spectrum of a 7.0 molal SbF /HPO F Solution at 3 0 ° 5 2 2 8 0 ( v i i ) FIGURE . PAGE 20. 1^F N.M.R. Spectra of the P-F Region f o r a 2 . 3 1 m o l a l SbF 5/HP0 2F 2 S o l u t i o n at 3 0 ° and - 7 0 ° 8 4 21. 19F N.M.R. Spectrum i n the Sb-F Region f o r a 2 . 3 1 molal ' SbF 5/HP0 2F 2 S o l u t i o n at - 7 0 (peak M) 85 22a) X 9 F N.M.R. Spectra i n the Sb-F Region f o r a 2 . 3 1 molal • SbF 5/HP0 2F 2 S o l u t i o n at - 7 0 ° (peaks K, L and P) 8 6 22b) ^F.N.M.R. Spectrum i n the Sb-F Region f o r a 2 . 3 1 molal SbF 5/HP0 2F 2 S o l u t i o n at - 7 0 ° (peaks N & 0) 8 7 2 3 . X 9 F High-Resolution N.M.R. Spectrum of the P-F Region f o r a 2 . 3 1 molal SbF 5/HP0 2F 2 S o l u t i o n at 3 0 ° 9 2 2 4 . 5 1 P N.M.R. Soectrum of a 2 . 6 2 molal•SbFr/HPO-F- S o l u t i o n a t 3 0 ° ? 93 2 5 . D e t a i l s of the 3 1 P N.M.R. Spectrum of a 2 . 6 2 molal SbF./ HP0 2F 2 S o l u t i o n at 3 0 ° 5 9 4 2 6 . Vacuum Line used f o r the Decomposition of KSbF^P0 2F 2 9 8 2 7 . C r y o s t a t , used f o r Nitrobenzene S o l u t i o n s 1 0 4 2 8 . Depression of Freez i n g P o i n t (AT) f o r Various Solutes i n Nitrobenzene 1 1 2 ' 2 9 . S p e c i f i c C o n d u c t i v i t i e s of Some Solutes in.Nitrobenzene at 25 1 16 3 0 . E q u i v a l e n t C o n d u c t i v i t i e s of Some E l e c t r o l y t e s i n Nitrobenzene at 2 5 ° 1 1 8 ( v i i i ) ACKNOWLEDGMENTS The a u t h o r w i s h e s t o e x p r e s s g r a t i t u d e t o D r . R. C. Thompson who f i r s t s u g g e s t e d t h e p r o b l e m , and u n d e r whose g u i d a n c e t h e work was d o n e . T h a n k s a r e due t o M r . S . Rak who c o n s t r u c t e d t h e g l a s s a p p a r a t u s , t o M r . R. B u r t o n who o p e r a t e d t h e H.A . .100 n . m . r . s p e c t r o m e t e r , t o M r . R. W o l f e who a s s i s t e d w i t h t h e o p e r a t i o n of t h e p l a t i n u m r e s i s t a n c e t h e r m o m e t e r and f i n a l l y t o M r . L . N e e r i n g f o r many h e l p f u l s u g g e s t i o n s . The g e n e r o u s g i f t o f d i f l u o r o p h o s p h o r i c a c i d b y t h e C z a r k - M a h o n i n g C h e m i c a l Company i s a l s o g r a t e f u l l y a c k n o w l e d g e d . CHAPTER I '• ..' -General I n t r o d u c t i o n At the t u r n of the century s o l u t i o n chemistry was l a r g e l y , concerned w i t h r e a c t i o n s c a r r i e d out i n aqueous media. During the past f i v e decades, however, s t u d i e s on a v a r i e t y of non-aqueous s o l v e n t s have r e s u l t e d i n the development of many new solvent systems. The experience so obtained has g r e a t l y broad-ened the scope of s y n t h e t i c chemistry and has co n s i d e r a b l y i n -creased the understanding of the p h y s i c a l and chemical p r o p e r t i e s of s o l u t i o n s . Although the number of so l v e n t s which have been i n v e s t i g a t e d i s very l a r g e , extensive and systematic s t u d i e s on the p h y s i c a l p r o p e r t i e s of s o l u t i o n s have been l i m i t e d to r a t h e r few s o l v e n t s , notably HF, H^SO^ and NH^ and to a sma l l e r extent -HSO^F, S0 2 and HC1. The purpose of the work described i n t h i s t h e s i s was to study the p r o p e r t i e s of s o l u t i o n s i n anhydrous d i f l u o r o p h o s p h o r i c a c i d and to i n v e s t i g a t e the p o s s i b i l i t y of HP0 2F 2 as a prepara-t i v e medium. At present, the range of s u i t a b l e and r e a d i l y a v a i l a b l e f l u o r i n a t e d s o l v e n t s of use f o r the pr e p a r a t i o n of f l u o r i d e s i s l i m i t e d e s s e n t i a l l y t o hydrogen f l u o r i d e , f l u o r o -s u l p h u r i c a c i d and bromine t r i f l u o r i d e and i t i s hoped th a t HP0 2F 2 w i l l extend t h i s range. 1.1 P r o p e r t i e s of d i f l u o r o p h o s p h o r i c a c i d The l i t e r a t u r e r e g a r d i n g d i f l u o r o p h o s p h o r i c a c i d has been reviewed r e c e n t l y 2 > 3 , 4 a n d a s l i t t l e f r e s h i n f o r m a t i o n has ap-peared s i n c e these reviews were w r i t t e n , the us u a l h i s t o r i c a l 2 r e v i e w o f t h e s o l v e n t w i l l be d i s p e n s e d w i t h . However-, a sum-mary o f t h e p h y s i c a l and c h e m i c a l p r o p e r t i e s o f HPO2F2 r e l e v a n t t o t h i s work w i l l be a t t e m p t e d . D i f l u o r o p h o s p h o r i c a c i d i s a m o b i l e , c o l o u r l e s s , c l e a r l i q u i d w h i c h fumes s t r o n g l y i n m o i s t 2 a i r ; some o f i t s p h y s i c a l p r o p e r t i e s a r e l i s t e d i n T a b l e 1. T a b l e 1 . P h y s i c a l P r o p e r t i e s o f D i f l u o r o p h o s p h o r i c A c i d P r o p e r t y V a l u e ( r e f e r e n c e 3) V a l u e ( t h i s work ) M e l t i n g p o i n t °C: ( i ) - 9 1 . 3 - 1 . 0 ( i i )-96.5 - 1 . 0 B o i l i n g p o i n t °C: ( i ) 108-111 ( i i )115 .9 42-43' a t 75mm. 50-52 a t 100mm. L i q u i d d e n s i t y {&/ml): d ^ 5 = 1.583 dj? 5 = 1 .583 v i s c o s i t y YJ ( p o i s e ) : 0 .0519 a t 26 . 0 1 ° 0 . 0 5 5 - . 0 0 3 a t 25.0° h e a t o f v a p o r i z a t i o n ( c a l . / m o l e ) : ( i ) 7 9 2 5 , UD9125 ( i i i ) 9 3 6 0 T r o u t o n c o n s t a n t : ( i ) 2 0 . 4 , ( i i ) 23.7 ( i i i ) . 2 4 . 6 I t i s a monobas ic a c i d i n w a t e r and i s s l o w l y h y d r o l y s e d w i t h t h e 5 f o r m a t i o n o f m o n o f l u o r o p h o s p h o r i c a c i d , H P 0 2 F 2 + H 2 0 —* HgPO^F + HF ( 1 . 1 ) . T r o t t e r e t a l . c a r r i e d ou t t h e f i r s t d e t a i l e d s t u d y o f t h e P0 2 F2~ i o n i n t h e i r s t r u c t u r e a n a l y s i s o f p o t a s s i u m d i f l u o r o p h o s p h a t e . ^ I t was f o u n d t h a t t h e r e i s d i s t o r t i o n o f t h e v a l e n c y a n g l e s i n t h e d i f l u o r o p h o s p h a t e s f r o m t h e r e g u l a r t e t r a h e d r a l v a l u e . The m o l e c u l a r shape o f monomeric H P 0 2 F 2 may, t h e r e f o r e , be assumed t o be a l s o a p p r o x i m a t e l y t e t r a h e d r a l . The degree of a s s o c i a t i o n of molecules i n a l i q u i d determines to no s m a l l extent i t s s o l v e n t p r o p e r t i e s and the evidence t h a t HPO2F2 i s a s t r o n g l y a s s o c i a t e d l i q u i d i s extensive. I n the s e r i e s of compounds shown below the molecular weight of each molecule i n each column I s approximately the same i . e . a f l u o r i n e atom has been r e p l a c e d by a hydroxyl group. -S-compounds b o i l i n g p o i n t (1 atm) S 0 2 F 2 H0S0 2F (HO) 2S0 2 -55.4 162.7 317 ( w i t h decom-p o s i t i o n ) P- compounds b o i l i n g point (1 atm); POF^ HOPOF, (H0) 2P0F (H0) 3P0 -39.8 116 (with decom-p o s i t i o n ) (cannot be d i s t i l l e d , some decom-p o s i t i o n at 180°) 213 (-|H20) The l a r g e change i n b o i l i n g point i s a t t r i b u t e d to molecular 7 a s s o c i a t i o n due t o hydrogen bonding . I n the sulphur s e r i e s of compounds the very high b o i l i n g point of H-SO compared to that 8 d k of HSOoF i s c o n s i s t e n t w i t h a higher degree of molecular a s s o c i a -te t i o n i n the former l i q u i d . I t would appear on the basis of i t s b o i l i n g p o i n t , t h e r e f o r e , t h a t d i f l u o r o p h o s p h o r i c a c i d i s exten-9 s i v e l y a s s o c i a t e d . L e n s k i i et a l . r e p o r t a value f o r the v i s -c o s i t y of HPO F of 5.31 c e n t i p o i s e ( c . f . I . 5 6 cp. f o r HSO F ) , 1 0 2 2 11 3 which i s f u r t h e r i n d i c a t i o n of solvent a s s o c i a t i o n . This a s s o c i a 1 p t i o n was f u r t h e r s t u d i e d by S t a f f o r d et a l . who examined the i n f r a r e d s p e c t r a of a number of h y d r o x y l i c a c i d s i n the l i q u i d and vapour s t a t e s and found the OH s t r e t c h i n g v i b r a t i o n s h i f t e d t o lower f r e q u e n c i e s on going from the vapour t o the l i q u i d . 4 I t was concluded t h a t i n the s e r i e s of compounds HNO^, HCIO^, HSO3F, CH3SO3H and H P 0 2 F 2 the s t r e n g t h of hydrogen bonding i s i n -d i c a t e d by the extent of the v a p o u r - l i q u i d s h i f t and that as the OH frequency s h i f t i s greatest f o r H P 0 2 F 2 i t probably forms the str o n g e s t hydrogen bonds. The Trouton constants of many non-associated l i q u i d s are of the order 2 1 . 5 , ^ w h i l e a s s o c i a t e d l i q u i d s commonly e x h i b i t somewhat greater v a l u e s . Consistent w i t h t h i s , the Trouton con-s t a n t of H P 0 2 F 2 i s approximately 24. F i n a l l y , evidence f o r hydrogen bonding may be obtained from the n.m.r. chemical s h i f t of p r o t o n i c l i q u i d s . 1 ^ I n the present work i t was found that the resonance of H P 0 2 F 2 occurs at - 3 . 3 5 T lower f i e l d even than t h a t found f o r HgSO^ (-1.6T). 1.2. Acid-base behaviour i n p r o t o n i c s o l v e n t s I t i s convenient to di s c u s s the chemistry of s o l u t i o n s i n p r o t o n i c s o l v e n t s i n terms of acid-base behaviour and a few com-ments concerning d e f i n i t i o n s of a c i d s and bases would be. r e l e v a n t at t h i s p o i n t . I t i s known tha t water i s not unique i n i t s a b i l i t y t o act as an i o n i z i n g solvent and as a medium f o r acid-base behaviour. Analogies among p r o t o n i c s o l v e n t s become apparent when 15 the a u t o - p r o t o l y s i s r e a c t i o n of each i s considered. Although such i o n i z a t i o n i s o r d i n a r i l y comparatively s m a l l , c o n d u c t i v i t y measurements have shown i t s e x i s t e n c e i n a number of in s t a n c e s . I n the t a b l e below the a u t o p r o t o l y s i s r e a c t i o n s of various s o l -vents are l i s t e d . 5 Solvent H20 H 20 + H 20 ^ H^0+ + 0H-NH3 NH^ + NH^ ^ NH^+ + NH 2~ HF HF +• HF ^ H 2 F + + F~ H 2S0 4 H 2S0 4 +' H 2S0 4 ^ H 3 S 0 4 + + HS0 4" HSO^F HSO^F + HSO^F ^ HgSC^F* + SO^F" Based upon such c o n s i d e r a t i o n s s e v e r a l d e f i n i t i o n s f o r aci d s and bases have been advanced i n terms of the parent s o l v e n t . 16,17,16* They can be combined to admit as an a c i d any m a t e r i a l g i v i n g , e i t h e r by d i r e c t d i s s o c i a t i o n or by i n t e r a c t i o n w i t h the s o l v e n t , the c a t i o n c h a r a c t e r i s t i c of the sol v e n t and as a base any m a t e r i a l g i v i n g the anion c h a r a c t e r i s t i c of the so l v e n t . N e u t r a l i z a t i o n , i n terms of the general theory of sol v e n t systems, amounts to the combination of the sol v e n t c a t i o n w i t h the solvent anion t o pro-duce the s o l v e n t . By analogy w i t h other p r o t o n i c s o l v e n t s a c i d behaviour i n HP0 2F 2 may be defined as the r e a c t i o n of a so l u t e t o produce H-the acidium i o n , H^PO^F^ and base behaviour as the r e a c t i o n t o produce the P 0 2 F 2 ~ i o n . These i o n s are the c h a r a c t e r i s t i c ions produced by solvent a u t o p r o t o l y s i s . 2HP0 2F 2 ^ H 2 P 0 2 F 2 + + P0 2F 2~ (1.2) There i s some evidence ( t o be given l a t e r ) f o r t h i s r e a c t i o n i n HP0 2F 2, however, the d e f i n i t i o n of ac i d s and bases i n t h i s solvent i s a c t u a l l y independent of whether or not t h i s r e a c t i o n takes place to a measurable extent. Difluorophosphates which i o n i z e to give P0 2F 2~, MP0 2F 2 ^ M + + P 0 2 F 2 " (1.3) and molecules which are protonated, B + HP0 2F 2 BH + + P 0 2 F 2 " (1.4) are bases i n t h i s system. Correspondingly, a c i d s are molecules which protonate HP0 2F 2, HA + HP0 2F 2 — H 2 P 0 2 F 2 + + A" (1.5) or molecules which accept difluorophosphate anions, A + 2HP0 2F 2 ^ A P 0 2 F 2 " + H 2 P 0 2 F 2 + (1.6) 1.3. O u t l i n e of present work. Chapter I I of t h i s t h e s i s i s concerned l a r g e l y w i t h the d e t a i l e d i n v e s t i g a t i o n of the nature of s o l u t i o n s of the a l k a l i and a l k a l i n e e a r t h metal difluorophosphates i n d i f l u o r o p h o s p h o r i c a c i d . This study has c l o s e l y f o l l o w e d that r e p o r t e d by G i l l e s p i e 19 and co-workers 7 on s o l u t i o n s of metal hydrogen sulphates i n s u l p h u r i c a c i d . Using a v a r i e t y of p h y s i c a l measurements these authors were able t o e l u c i d a t e the nature of these s o l u t i o n s . From e l e c t r i c a l c o n d u c t i v i t y , t r a n s p o r t number and f r e e z i n g -p o i n t depression measurements they were able t o show, f o r example t h a t the metal hydrogen sulphates are f u l l y d i s s o c i a t e d e l e c t r o -l y t e s , the degree of s o l v a t i o n of the a l k a l i metal c a t i o n s de-creases w i t h i n c r e a s i n g c a t i o n s i z e and the hydrogen sulphate anion conducts e l e c t r i c i t y by a p r o t o n - t r a n s f e r mechanism. P r o t o n a t i o n r e a c t i o n s of organic molecules i n sol v e n t s of high a c i d i t y such as HF, 2 0 HSO^F 1 0 and H 2S0^ 2 1 have been s t u d i e d e x t e n s i v e l y . Chapter I I I d e s c r i b e s e l e c t r i c a l c o n d u c t i v i t y s t u d i e s on p r o t o n a t i o n r e a c t i o n s of organic bases i n HP0 2F 2. E l e c t r i c a l c o n d u c t i v i t y s t u d i e s on s o l u t i o n s of miscellaneous 7 i n o r g a n i c compounds are a l s o described i n t h i s chapter. 3 Although HPC^Fg i s a strong a c i d i n H 20 , s t u d i e s of s o l u -77 t i o n s of H P 0 2 F 2 i n H 2S0^ have shown H P 0 2 F 2 t 0 b e a w e a k e r a c i d than both HgSO^ . and HSO^F and t h e r e f o r e a wider range of s o l u t e s which would behave as a c i d s i n H P 0 2 F 2 should be a v a i l a b l e . Chapter IV i s concerned w i t h a c i d behaviour i n H P 0 2 F 2 and a c i d -base r e a c t i o n s i n t h i s s o l v e n t . F a c t o r s which determine the r e l a t i v e orders of a c i d 22 strengths are not w e l l understood. Previous work has estab-l i s h e d the order HSO^F > H 2S0^ > H P 0 2 F 2 ; however i t i s s i g n i f i -cant t h a t t h i s order i s e s t a b l i s h e d only f o r the case where the bulk solvent i s a p r o t o n i c medium. I n an attempt to determine the r e l a t i v e proton-donating a b i l i t i e s of these a c i d s i n non-p r o t o n i c media, s o l u t i o n s of the a c i d s were s t u d i e d i n n i t r o -benzene as solvent and t h i s work i s described i n chapter V. CHAPTER I I S o l u t i o n s of M e t a l Difluorophosphates 2.1 I n t r o d u c t i o n The a l k a l i and a l k a l i n e earth metal difluorophosphates may be expected to act as strong bases according t o (1.3) when d i s s o l v e d i n d i f l u o r o p h o s p h o r i c a c i d . I t i s not p o s s i b l e , however, to p r e d i c t the degree of d i s s o c i a t i o n of these s a l t s i n t o f r e e i o n s , p a r t i c u l a r l y as the d i e l e c t r i c constant of HPC^Fg i s not known. I n an attempt to o b t a i n an understanding of the degree and nature of i o n - s o l v e n t and i o n - i o n i n t e r a c t i o n s ( i . e . i o n - p a i r formation) i n t h i s s o l v e n t , e l e c t r i c a l c o n d u c t i v i t y , v i s c o s i t y , d e n s i t y , and n.m.r. s t u d i e s on s o l u t i o n s of metal d i f l u o r o p h o s -4 phates and r e l a t e d compounds have been c a r r i e d out. E a r l i e r work has described e l e c t r i c a l c o n d u c t i v i t y s t u d i e s on s o l u t i o n s of t h e . a l k a l i metal difluorophosphates. Because of i t s importance t o the present work and the f a c t t h a t i t i s as yet unpublished and hence.not r e a d i l y a v a i l a b l e , the r e s u l t s w i l l a l s o be given i n d e t a i l here. (Table 2) 2.2 Experimental A) P r e p a r a t i o n and p u r i f i c a t i o n of m a t e r i a l s . 1.- Difluorophosphoric a c i d Commercial HPO2F2, s u p p l i e d by Ozark-Mahoning Chemical Company, T u l s a , Oklahoma, was p u r i f i e d by double d i s t i l l a t i o n at a pressure of 100 mras. of mercury and a temperature range of 50-52° i n the apparatus shown i n F i g . 1. A more d e t a i l e d F i g . 1. Difluorophosphoric Acid- D i s t i l l a t i o n Apparatus 10 d e s c r i p t i o n of the procedure i n v o l v e d i n p u r i f y i n g the a c i d was 4 given p r e v i o u s l y . i i M e t a l difluorophosphates • * The p r e p a r a t i o n of anhydrous a l k a l i metal d i f l u o r o p h o s -phates by the r e a c t i o n of a l k a l i metal c h l o r i d e s w i t h d i f l u o r o -phosphoric a c i d according t o , MCI + HP0 2F 2 -* MP0 2F 2 + HC1 (2.1) was re p o r t e d previously.^" I n the present work anhydrous ca l c i u m and barium difluorophosphates were prepared i n an analogous manner by the r e a c t i o n of the a l k a l i n e earth metal c h l o r i d e s ( p r e v i o u s l y d r i e d by heating t o 190° f o r 18 hours i n an oven and s t o r e d over phosphoric oxide i n a vacuum d e s i c c a t o r ) w i t h the a c i d . The samples were stored over phosphoric oxide i n a vacuum d e s i c c a t o r u n t i l used. Microanalyses were obtained from the A. Bernhardt M i c r o a n a l y t i c a l L a b o r a t o r i e s , Germany and the r e s u l t s are g i v e n below: C a ( P 0 2 F 2 ) 2 B a ( P 0 2 F 2 ) 2 c a l c u l a t e d obtained c a l c u l a t e d obtained %? 25.60 25 .43 16.26 16 .39 %F 31 .40 31.65 22 .40 22 .70 %Ba 40.4.6 40.35 B) E l e c t r i c a l C o n d u c t i v i t y The design of the c e l l used t o measure the c o n d u c t i v i t i e s of s o l u t i o n s i n d i f l u o r o p h o s p h o r i c a c i d i s shown i n F i g . 2. The c e l l could be attached t o the d i s t i l l a t i o n apparatus at K by means of the B19 ground g l a s s cone L. The c e l l has two el e c t r o d e s and F i g . 2 E l e c t r i c a l C o n d u c t i v i t y C e l l a c e l l constant of approximately 6. The c a p a c i t y of the c e l l was about 400 mis.. The c e l l was cleaned w i t h aqua-regia and the el e c t r o d e s were p l a t e d w i t h platinum blarcR* by e l e c t r o l y s i n g a c h l o r o -p l a t i n i c a c i d s o l u t i o n prepared according t o Jones and B o l l i n g e r . The s o l u t i o n c o n s i s t e d of a 0.3% s o l u t i o n of c h l o r o p l a t i n i c a c i d i n 0.025N h y d r o c h l o r i c a c i d w i t h 0.02$ l e a d acetate added. A current of t e n m i l l i a m p s . was passed f o r f i f t e e n minutes w i t h a r e v e r s a l of current every t e n seconds. The c e l l was steamed out, d r i e d and then c a l i b r a t e d u s i n g aqueous potassium c h l o r i d e s o l u -t i o n according t o the method of L i n d , Zwolenik and Fuoss. The c e l l was r e p l a t e d and r e c a l i b r a t e d p e r i o d i c a l l y . A l l measurements were made w i t h the c e l l immersed i n an o i l bath r e g u l a t e d by means of a mercury-thallium thermo-regula'tor at 25 i . 0 0 2 ° . The temperature of the o i l bath was measured by Beckmann thermometers which had been c a l i b r a t e d against a p l a t i -num r e s i s t a n c e thermometer. For the a d d i t i o n of s o l i d m a t e r i a l t o the c e l l the ap-paratus shown i n F i g . 3 was used. I t c o n s i s t e d of a 'T'-shaped g l a s s tube, w i t h B 19 ground g l a s s sockets at the ends 0 and P, and a B 24 ground g l a s s cone w i t h an exte n s i o n at M. The corks at 0 and P were made of T e f l o n and they were t i g h t l y f i t t e d w i t h s t a i n l e s s s t e e l p i s t o n s A and B r e s p e c t i v e l y . The f l a t 'runners' which were a l s o made from T e f l o n i n t e r l o c k e d at Q and.lay'on the bottom of the g l a s s tubes. The compound t o be added t o the c e l l was weighed i n t o s m a l l , preweighed, dry g l a s s boats which were st o r e d i n the si d e arm. I t was found t h a t approximately ei g h t "to minimize p o l a r i s a t i o n e f f e c t s . F i g . 3 I n j e c t o r , , used f o r Solute A d d i t i o n s t o the C o n d u c t i v i t y C e l l boats could be accommodated i n the s i d e arm. I f the s o l u t e was thought t o be hygroscopic the samples were weighed out i n the dry box. However, t o remove any water which may have been ab-sorbed i n the weighing-out process the loaded i n j e c t o r was connected t o a vacuum pump v i a l i q u i d n i t r o g e n t r a p s , warmed and evacuated. The i n j e c t o r was detached from the pump a f t e r a few hours and st o r e d u n t i l use i n the dry box. A c o n d u c t i v i t y run was c a r r i e d out i n the f o l l o w i n g man-ner: by means of a B 3-9 in n e r ground g l a s s j o i n t the conduc-t i v i t y c e l l was attached t o the d i s t i l l a t i o n apparatus at K and f l u s h e d out w i t h dry a i r . D i f l u o r o p h o s p h o r i c a c i d was d i s t i l l e d d i r e c t l y i n t o the c e l l and a c i d obtained i n t h i s way u s u a l l y had —L —1 —1 a c o n d u c t i v i t y of about' 2.6 x 1 0 o h m s " cm7 * At a l l times i n han d l i n g the a c i d great care was taken to exclude water. I n a t e s t run on the pure a c i d , a gradual i n c r e a s e i n the s p e c i f i c c o n d u c t i v i t y occurred w i t h time; over a p e r i o d of seven hours a 0.5% in c r e a s e i n Ji. was observed'! S o l u t i o n s f o r c o n d u c t i v i t y measurements were prepared as f o l l o w s : d i f l u o r o p h o s p h o r i c a c i d was d i s t i l l e d d i r e c t l y i n t o the c e l l which was weighed before and a f t e r a d d i t i o n of a c i d . The B 21+ stopper was removed and the i n j e c t o r was q u i c k l y i n s e r t e d i n t o the c e l l at F. Mercury • was poured i n t o the g l a s s tubes h o l d i n g the platinum e l e c t r o d e s and then the c e l l and i n j e c t o r were placed on a stand i n the o i l bath. A d d i t i o n of s o l u t e was achieved by pushing a g l a s s boat from the s i d e arm i n t o the main tube by the p i s t o n A and then the boat was moved by p i s t o n B along N and. pushed i n t o the a c i d . •^perhaps due to water i m p u r i t y . , The c e l l was w e l l shaken a f t e r each a d d i t i o n of s o l u t e t o ensure good mixing and then returned t o the o i l bath. A f t e r s u f f i c i e n t time had elapsed t o a l l o w f o r temperature e q u i l i -brium ( f i f t e e n minutes) the r e s i s t a n c e measurements were made. The c e l l was then removed from the bath, reshaken, and the con-d u c t i v i t y redetermined u n t i l no f u r t h e r change i n r e s i s t a n c e was observed. I n t h i s way v a r i a t i o n s i n c o n d u c t i v i t y due t o improper mixing were e l i m i n a t e d . L i q u i d s o l u t e s were added to the c e l l by means of a 2ml. microburette (R.G.I. Inc.) shown i n F i g . 4. A T e f l o n adaptor was constructed ( i n s e t F i g . 4) so tha t the microburette could be attached to the c e l l ; i t c o n s i s t e d of a T e f l o n sleeve w i t h a B 19 socket at one end and a T e f l o n nut c o n t a i n i n g a V i t o n '0* r i n g . The adaptor was he l d at p o s i t i o n B on the g l a s s b a r r e l of the burette by p l a c i n g the T e f l o n nut, A, c o n t a i n i n g the T0 T r i n g at B and screwing up the sleeve i n t o the nut u n t i l i t was he l d f i r m l y and d i d not s l i p down the gl a s s t i p . The dry micro-b u r e t t e and l i q u i d s o l u t e were placed i n the dry box. The bu r e t t e was r i n s e d out and then f i l l e d w i t h the s o l u t e . The g l a s s t i p was wiped and then capped w i t h a tube f i t t e d w i t h a B 19 cone which f i t t e d i n t o the T e f l o n B 19 socket sleeve. The apparatus was removed and attached to the c e l l , the tube being removed at the l a s t moment. A d d i t i o n s were made by screwing up the plunger and n o t i n g the i n i t i a l and f i n a l volumes. By making use of the d e n s i t y of the s o l u t e the mass of the a d d i t i o n and thus the r e s u l t i n g m o l a l i t y of the s o l u t i o n could be determined. Resistances of s o l u t i o n s were measured on a p r e c i s i o n F i g . k M i c r o b u r e t t e , used f o r Solute A d d i t i o n s to the C o n d u c t i v i t y C e l l 16 in f> cr O SiiuiWLi MM B 17 a~c r e s i s t a n c e bridge which has been p r e v i o u s l y described by 25 Daggett. A 2000c/s o s c i l l a t o r was employed as the source and a telephone headset was used as the n u l l d e t e c t o r . Throughout t h i s work, s p e c i f i c c o n d u c t i v i t y w i l l be r e f e r r e d t o by the symbol J{_ .. Some measurements were made at 1000 c/s and these gave s a t i s f a c t o r y agreement w i t h those at 2000 c/s. C) Nuclear magnetic resonance (n.m.r.) A d e s i r e d amount of s o l u t e was added to a weighed, dry n.m.r. tube (Varian A s s o c i a t e s , a n a l y t i c a l n.m.r. sample tube, part no. 9 0 5 - 3 7 0 ) of 0 . 5 cm.o.d. which was then reweighed and t r a n s f e r r e d t o a dry box. About 1 m l . of HPO2F2 was added to the tube which was again reweighed. The tube was once more r e -turned t o the dry box where a c a p i l l a r y tube ( 0 . 1 5 cm.o.d.) of H P 0 2 F 2 used as an e x t e r n a l reference was added. During these handling procedures the tube was t i g h t l y capped. F i n a l l y the n.m.r. tube was * flame sealed* and s t o r e d i n l i q u i d , n i t r o g e n u n t i l the s p e c t r a were run ( i t u s u a l l y took 4 - 5 days t o ob-t a i n a l l the s p e c t r a ) . I t was found t h a t a d d i t i o n of the HPQ^Fj ex-t e r n a l r eference to a n.m.r. tube of HPO2F2 caused no new reson-ances t o appear i n the f l u o r i n e or phosphorus s p e c t r a . The chemical s h i f t s , r e l a t i v e t o the pure s o l v e n t , were measured w i t h a V a r i a n HA 100 h i g h - r e s o l u t i o n spectrometer,• operating at 1 0 0 . 0 Mc/s f o r 1H, 9 4 . 0 7 f o r 1 9 F and 4 0 . 4 3 f o r 3 1 P . Chemical s h i f t s were measured by the * side-band* technique, i n the case of the phosphorus and proton s p e c t r a and on c a l i b r a t e d , chart paper f o r the f l u o r i n e s p e c t r a . I n the "^F s p e c t r a the r e g i o n around each peak of the doublet was-examined by l o c k i n g - i n on the other peak of the doublet. 18 D) V i s c o s i t y -V i s c o s i t y measurements of s o l u t i o n s of s e v e r a l metal d i -fluorophosphates i n d i f l u o r o p h o s p h o r i c a c i d as solvent were c a r r i e d out at 25°. S o l u t i o n s were made up i n the drybox by add-i n g a weighed amount of HP0 2F2 to a known weight of the metal d i -fluorophosphate contained i n a t e s t tube which was then thorough-l y shaken. I n a l l cases the d e n s i t y and v i s c o s i t y determina-t i o n s were made on the same s o l u t i o n . 26 A standard Ostwald viscometer was employed which was c a l i b r a t e d u s i n g d i s t i l l e d water and dimethyl sulphoxide as standards. The temperature was c o n t r o l l e d by p l a c i n g the v i s c o -meter i n a 25-0.1° waterbath. To make sure that the d r y i n g tubes which f i t t e d on the openings of the viscometer and would be needed f o r the HPO2F2 determinations would not a f f e c t the r e s u l t s s e v e r a l measurements were taken using the c a l i b r a t i n g l i q u i d s w i t h the d r y i n g tubes i n p o s i t i o n as w e l l as removed. No d i f f e r e n c e i n the r e s u l t s was observed. The viscometer was f i r s t washed w i t h concentrated n i t r i c a c i d and then s e v e r a l times w i t h d e i o n i z e d water; i t was then d r i e d and flushed-out w i t h dry a i r f o r 1-2 hours. Ten mis. of l i q u i d were p i p e t t e d i n t o the wide bore tube of the viscometer which was placed u p r i g h t i n the water bath and then l e f t f o r an hour t o a t t a i n 25° - the tubes being capped to prevent evapora-t i o n before measurements were made. Several runs were made on each s o l u t i o n u n t i l c o n s i s t e n t r e s u l t s were obtained. Great care was taken t o make sure t h a t no dust p a r t i c l e s were trapped i n the c a p i l l a r y . I n the case of the HP0oF s o l u t i o n s the viscometer was charged w i t h the s o l u t i o n i n the dry box. E) Density The c l e a n , dry s p e c i f i c g r a v i t y b o t t l e s of 10 mis. capa-c i t y were weighed and then f i l l e d w i t h l i q u i d . The b o t t l e was then suspended t o i t s neck i n the water bath and l e f t f o r an hour. On f u r t h e r examination i t was u s u a l l y found t h a t the l i q u i d l e v e l was mid-way up the c a p i l l a r y of the stopper. The c a p i l l a r y was f i l l e d by means of a f i n e p i p e t t e . Excess l i q u i d which expanded out through the c a p i l l a r y was mopped up by t i s s u e paper. 'When it.appeared t h a t the b o t t l e and c a p i l l a r y were f u l l of l i q u i d and at 25° the b o t t l e was removed and placed i n a beaker of c o l d water. The b o t t l e was then thoroughly d r i e d and weighed. This procedure was repeated three times f o r each determination. To c a l i b r a t e the b o t t l e s , l i q u i d s of a c c u r a t e l y known d e n s i t y were used, namely mercury and water, care being taken to exclude a l l a i r bubbles. For the s o l u t i o n s i n d i -f l u o r o p h o s p h o r i c a c i d the weighed d e n s i t y b o t t l e was f i l l e d i n the dry box and then t r a n s f e r r e d t o the water bath. 2.3 R e s u l t s and d i s c u s s i o n A) E l e c t r i c a l c o n d u c t i v i t y The r e s u l t s of the c o n d u c t i v i t y measurements on s o l u t i o n s of metal difluorophosphates i n d i f l u o r o p h o s p h o r i c a c i d at 25° are given i n Table 2. As a l l the s o l u t i o n s were made up by weight the concentrations are expressed i n molal u n i t s , m. I n each case a p l o t of the s p e c i f i c conductance, X. against m o l a l i t y was made ( F i g . 5 ) . As de n s i t y and v i s c o s i t y data are 20 TABLE 2 •SPECIFIC CONDUCTANCES OF SOME DIFLUOROPHOSPHATES AT 2 5°C L i P 0 2 F 2 10 dm ohm. .cm. 9K P 0 2 F 2 10 ^ m ohm. cm. RbP0 2F 2 102m l O 2 ^ .ohm cm. ^ " 0 . 0 0 0 0.306 1.020 2.190 4.429 6.773 9.733 13.91 19.69 27.66 37 .20 4 9 . 3 4 6 0 . 0 8 70.55 2.482 2.673 3 .464 4 .528 6 .379 8.086 10.15 12.73 16.59 20 .46 24 .43 29.18 3 2 . 2 1 34 .56 NaP0 2F 2 102m lO1^ 0.000 0.222 0.761 2.859 6.003 8.220 11.16 15.13 20.95 25.36 31.37 3 6 . 3 3 42.46 47.79 ohm;"Icm.~1 2.503 2.557 2.868 4 . 5 0 0 6.794 8.266 10.12 12.26 15.15 17.96 20.67 22.81 24.75 26.40 0.000 0.158 0.566 1.366 2.435 4.043 6.054 9.310 13.33 18.53 23.88 29.65 34.37 4 0 . 2 8 48.26 2.410 2.557 2.740 3.153 3.889 4.925 5.939 7.658 10.10 12.79 15.21 17.77 19.82 22.46 24.27 NH^P0 2F 2 102m 1 0 ^ 0.000 1.977 5.864 11.44 18.75 27.15 3 5 .60 ohm. -lcm.-l 2.473 3.546 5.351 9.110 13.35 13 .71 23.91 B a ( P 0 2 F 2 ) 2 10 2m 1 0 ^ ohm.~^cm. 0 . 0 0 0 2.823 1.736 3.783 6.033 8.075 7.646 9 .800 1 0 . 0 8 12.39 13.44 15.29 16.02 17.12 2 0 . 0 8 20.21 24.23 22.70 -1 0.000 6.629 2.051 4.056 7.084 11.22 I 6 . 8 4 23.63 31.88 2.499 2.662 3.313 4.314 5.325 7.329 10.56 13.81 17.72 10 2m 0.000 O.468 1.409 3.191 6.155 9.751 13.48 17.92 24.29 CsP0 2F 2 104U ohm. cm. 2.443 2.565 2.923 3.708 5.041 6.665 8.395 10.51 13.64 1 0 2 m 0.000 1.120 2.470 4.327 7.533 10.79 14.83 19.66 23.50 C a ( P 0 2 F 2 ) 2 lcAtt ohm_J- cm 2.553 2.758 4.628 5-793 8.676 10.30 11.77 13.53 14.27 -1 22 available f o r solutions of L i P 0 2 F 2 , KP0 2F 2, RbP0 2F 2 and B a ( P 0 2 F 2 ) 2 (see l a t e r ) , equivalent conductivities could be calculated f o r these solutes and these are given i n Table 3 , and i n F i g . 6 plots of equivalent conductance versus the square root of io n i c strength are shown. The equivalent conductance values, A , were c a l c u l a -t e d from the expression, TV = lOQoXi c • ' where C i s the concentration i n gram equivalents per l i t r e . The value of X i , the s p e c i f i c conductivity caused by the addition of solute, was calculated f r o m X i = X. —X,o, the observed conduc-tance l e s s the conductance value at i n f i n i t e dilution 1'! For the a l k a l i metal d i f luorophosphates K.o was taken as 2.25 x 10~^ 'ohm~"'"cm7^  but f o r the calcium and barium s a l t s values for l ^ o were 2.15 and 1 .90 x 10"^ ohm~x cm, . These equivalent conducti-v i t y values may be corrected f o r the change i n the bulk v i s -i s o c o s i t y of the s o l u t i o n by m u l t i p l y i n g by Vj /yj } where Yj the v i s c o s i t y of the pure solvent and Yj the v i s c o s i t y of the s o l u t i o n . 2 7 The A r j values are a l s o given i n Table 3; the e f f e c t of the v i s c o s i t y c o r r e c t i o n causes a lowering of the equi v a l e n t c o n d u c t i v i t y v a l u e s , which i s greatest f o r the more concentrated s o l u t i o n s . I n the case of C a ( P 0 2 F 2 ) 2 s o l u t i o n s n e i t h e r d e n s i t y nor v i s c o s i t y measurements were made, thus no v i s c o s i t y c o r r e c t i o n can be a p p l i e d and the equivalent conduc-t i v i t i e s ( c f . Table 3 ) were c a l c u l a t e d assuming the same value f o r the s o l u t i o n s as t h a t of the pure s o l v e n t , 1.5$3g./ml. The most s t r i k i n g f e a t u r e of these r e s u l t s i s t h a t the c o n d u c t i v i t y values are con s i d e r a b l y s m a l l e r than those obtained TABLE 3 EQUIVALENT CONDUCTANCES OF SOME ELECTROLYTE'S AT 25° L i P 0 2 F 2 io2c ioc^ 10*00., A ^Vlc ohm." era." 1 * O .484I • 0 .6958 0.423 8 .739 8.687 1.613 1 .270 1.214 7.526 7 .383 3 .459 1 .859 2 .278 6.585 6 .269 6.984 2.643 4 .129 5.912 5.404 10.66 3 .265 5.836 5-475 4 . 8 5 1 15 .29 3 .910 7 . 9 0 . 5.167 4 .438 21.78 4 .667 10.48 4 - 8 1 1 4-070 30.69 5-540 14.34 4-671 3 .910 42.89 6.549 18 .21 4 .245 3 -553 57 -24 7-566 22 .23 3-683 3-240 7 6 . 0 0 8 .718 26.93 3.542 2.940 K P 0 2 F 2 10 2C 10C2 1 0 S . -1 ohm cm. A 0 .2500 0 .5000 0.307 12.26 12.27 0 .6953 0 .9462 0.490 5.474 5.458 2.112 1-454 0.903 4.276 4.233 3.925 1.961 1.639 4-175 4.092 6.379 2.526 2.675 4-193 4.046 9.537 3.086 3.669 3.668 3.655 14.63 3-625 5.406 3-697 3.390 21.66 4 .654 7.65 3.624 3-182 28 .93 5-379 10.54 3-643 3-071 37.13 6.093 12.96 3.490 2.855 45-91 6.776 15.52 3-360 2.643 53-04 7.283 17.57 3-312 2.524 61.92 7.669 20.21 3 .268 2.445 73-77 6.569 22.02 2.988 2.384 RbP0 2F 2 10 2C 10C2 ohm._J-cm. -1- . 1.011 1.005 0.412 4.075 3.241 1 .800 1.068 3-295 6.399 2 .530 2.064 3.225 11.14 3 .336 3.575 3.209 17-60 4.195 5.579 3.170 26.29 5.128 8.31 3.161 36 .71 6.059 11.56 3.149 49 .22 7.015 15.47 3.143 A v 3.976 3.193 3.036 2.880 2.729 2.665 2.623 2.595 TABLE 3 (cont'd) B a ( P 0 2 F 2 ) 2 1 0 2 C 10C~2 1 0 43il A ohm."cm."1 2.738 2.867 1.883 3.436 9.453 5.326 6.175 3.265 1 1 . 9 4 5.986 7 . 9 0 0 3-308 1 5 - 6 7 6.857 1 0 . 4 9 3-347 20.78 7 - 9 0 0 1 3 - 3 9 3-221 2 4 . 6 7 8.603 1 5 - 2 2 3-084 3 0 . 7 2 9-601 1 8 . 3 1 2.980 36.83 1 0 . 5 1 20.80 2.823 1 . 7 6 8 1 1 1 ? ? 1 6 . 6 5 2 2 . 6 7 2 9 . 7 1 3 5 . 2 0 C a ( P 0 2 F 2 ) 2 2 . 3 0 4 W5 7 . 0 6 9 8 . 2 4 7 9 . 4 4 2 1 0 . 2 8 1 . 7 1 9 25 F i g . 6 E q u i v a l e n t C o n d u c t i v i t i e s of Some Difluorophos-phates at 25° p l o t t e d against the Square Root of the I o n i c Strength f o r strong bases i n other a s s o c i a t e d p r o t o n i c s o l v e n t s . Table 4 compares values of s p e c i f i c conductances at 0 . 1 molal concen-t r a t i o n f o r stro n g bases i n va r i o u s s o l v e n t s . TABLE 4 S p e c i f i c Conductances of Some Potassium S a l t s i n Various Solvent Solvent HP0 2F 2 Z" HSO^F 10 Solute KP0 2F 2 KSO^F S p e c i f i c conductance of 0.1m s o l u t i o n H 2 S 0 4 1 9 H 2 0 28 KHSO KOH 4 7 .81 220 200 275 x l O ~ 4 xlO - 4 x l O " ^ xlO-4-The lower c o n d u c t i v i t y values observed f o r the HP0 2F 2 s o l u t i o n s are e i t h e r due t o i o n i c m o b i l i t i e s i n HP0 2F 2 being much l e s s than those i n the other s o l v e n t s l i s t e d i n the Table or el s e due to the metal difluorophosphates being incompletely d i s s o c i a t e d e l e c t r o l y t e s i n HPOgFg. Since the d i e l e c t r i c constant of HPOgFg i s not knovm, making i t impossible t o p r e d i c t the importance of i o n p a i r i n g i n t h i s s o l v e n t , the r e s u l t s w i l l be examined on the b a s i s of two models: ( i ) i o n - p a i r i n g i s not important i n t h i s s o l v e n t and the metal difluorophosphates are f u l l y d i s s o c i a t e d e l e c t r o l y t e s , ( i i ) i o n - p a i r i n g i s important and the metal d i -fluorophosphates are incompletely d i s s o c i a t e d i n t o f r e e i o n s . Model ( i ) I n s o l v e n t s where the m o b i l i t i e s of the a u t o p r o t o l y s i s ions are much greater than the mobilities of other ions (because of a proton transfer mechanism of conduction for the former ions) strong bases exhibit almost identical specific conductivity curves at low concentrations with small deviations noticeable only i n more concentration solutions. As the conductivity curves for the a l k a l i metal and alkaline earth metal difluorophos phates deviate from each other at even the lowest concentrations measurable, i t must be concluded that, i f the difluorophosphates are f u l l y dissociated, the PO2F2*" ion does not show abnormal conduction. This conclusion i s consistent with the low conduc-t i v i t i e s observed for these solutions but i s surprising i n view of the associated nature of the solvent. The conductivity of the a l k a l i metal difluorophosphates decreases in the order Li)>Na^ NH^} Rb^ > Cs at any given con-centration. As each solute has the common ion, P O 2 F 2 " , then the differences i n the conductivity must be due to differences i n the mobilities of the cations i f i t i s assumed that complete dissociation of these salts occurs. This order of cation mobility i s opposite to that found by Gillespie et a l . in their 10 29 conductivity measurements in HSO^F and HgSO^ solutions where they found the order Cs^ > Rb)> Nh\^<v K/>Na)> L i prevailed. Gillespie has suggested that the lighter members have the larger solvated ion size, therefore accounting for their lower mobilities. For solutions of al k a l i metal difluorophosphates i n HPO^F^, assuming complete dissociation, i t must be concluded that the smallest cation has the greatest mobility and i s hence the least s o l -vated'— a surprising and indeed questionable result. Moreover i f i t i s assumed th a t the a l k a l i n e earth difluorophosphates are a l s o completely d i s s o c i a t e d i t f o l l o w s t h a t the m o b i l i t y of the Ca i o n i s l e s s than the m o b i l i t y of the Ba ^ i o n i . e . the sm a l l e r i o n has the smaller m o b i l i t y , a r e v e r s a l of the s i t u a -t i o n noted above f o r the a l k a l i metal c a t i o n s . Model ( i i ) I f i t i s assumed that i o n - p a i r i n g i s important i n HPO2F2 and the metal difluorophosphates are only weakly d i s s o c i a t e d i n t h i s s o l v e n t , then the r e l a t i v e orders of the c o n d u c t i v i t y values of these s a l t s may r e f l e c t t h e i r r e l a t i v e degrees of d i s s o c i a t i o n . 30 I n water } where i o n - p a i r i n g i s general though not extensive, f o r the a l k a l i metal s a l t s of the oxy-acids the metals of higher atomic number show more i o n - p a i r i n g . Thus cesium s a l t s tend t o e x h i b i t more i o n - p a i r i n g than l i t h i u m s a l t s and consequently produce fewer i o n s i n s o l u t i o n . I f t h i s tendency of i o n - p a i r i n g were to occur i n HPO2F2 then l i t h i u m difluorophosphate would be. the most d i s s o c i a t e d and would be expected t o e x h i b i t the highest conductance of the a l k a l i metal s a l t s , as i s observed. The s p e c i f i c c o n d u c t i v i t y curves f o r cal c i u m and barium difluorophosphates ( F i g . 5 ) show considerable curvature w i t h Ca^Ba and at s i m i l a r c oncentrations barium shows a greater con-ductance than calcium. I f i t i s assumed th a t these c o n d u c t i v i t y curves simply r e f l e c t the d i f f e r e n c e s i n degrees of d i s s o c i a t i o n of these s o l u t e s then c l e a r l y B a ( P 0 2 F 2 ) 2 i s the most d i s s o c i a t e d . I n the previous d i s c u s s i o n of the p o s s i b i l i t y of i o n - p a i r i n g i n the a l k a l i metal s a l t s i t would seem that f o r the Group I I metals w i t h the in c r e a s e i n c a t i o n i c charge, the formation of i o n - p a i r s i n q u i t e d i l u t e s o l u t i o n s would be the r u l e r a t h e r than the 3 0 exception. Davies r e p o r t s t h a t i n water, f o r s a l t s of the i n -organic oxy-acids, i o n - p a i r i n g i n c r e a s e s w i t h atomic number and i o n i c r a d i u s of the c a t i o n , as f o r the Group I metals. This shows t h a t - i o n - a s s o c i a t i o n cannot be explained by a purely e l e c t r o s t a t i c theory i n which the solvent f u n c t i o n s only as a medium of uniform d i e l e c t r i c , f o r i f so, the s m a l l e s t ions would show most i o n - p a i r i n g . However, Davies a l s o r e p o r t s that f o r .the hydroxides, f l u o r i d e s and carboxylates of the a l k a l i n e earth metals the opposite order p r e v a i l s , the l a r g e r barium i o n g i v i n g the l e a s t i o n - p a i r i n g . This order i s c o n s i s t e n t w i t h the r e s u l t s given here i n th a t the barium s a l t shows greater c o n d u c t i v i t y than the calcium s a l t at the same co n c e n t r a t i o n and so i s pre-sumably more d i s s o c i a t e d . I n view of the f a c t that the s p e c i f i c c o n d u c t i v i t y of H P O 2 F 2 i s high ( i n f a c t of the same order of magnitude as the s p e c i f i c c o n d u c t i v i t i e s of d i l u t e s o l u t i o n s of the metal d i -fluorophosphates) and as i t i s not known whether solvent s e l f -d i s s o c i a t i o n or i m p u r i t i e s are g i v i n g r i s e t o t h i s c o n d u c t i v i t y , q u a n t i t a t i v e treatment of the c o n d u c t i v i t y data i s d i f f i c u l t . Lack of i n f o r m a t i o n on the d i e l e c t r i c constant of HPC^Fg adds t o the d i f f i c u l t y of t r e a t i n g th£sedata. When the s p e c i f i c con-d u c t i v i t y curves are e x t r a p o l a t e d t o i n f i n i t e d i l u t i o n i t i s noted that the curves do not pass through the o r i g i n nor through the p o i n t corresponding to i n i t i a l s olvent c o n d u c t i v i t y . I f i t i s assumed t h a t the e x t r a p o l a t e d c o n d u c t i v i t y values are due t o i m p u r i t i e s i n the solvent and the d i f f e r e n c e between these values and the o r i g i n a l s olvent c o n d u c t i v i t y values are due t o r e p r e s s i o n of s o l v e n t a u t o p r o t o l y s i s then c o n d u c t i v i t y values — Xx> may be taken as reasonable values f o r the conduc-t i v i t y of added s o l u t e . Using these IKi*-values equivalent con-d u c t i v i t y values f o r the metal difluorophosphates have been c a l -c u l a t e d and are p l o t t e d against the square root of the i o n i c s t r e n g t h i n F i g . 6. Q u a l i t a t i v e l y i t can be seen t h a t at high concentrations the equivalent c o n d u c t i v i t i e s converge f o r the v a r i o u s s o l u t e s w h i l e at low values of i o n i c strength the curves diverge w i t h a greater i n c r e a s e i n «/V on d i l u t i o n f o r L/LPO2F2 c o n s i s t e n t w i t h t h i s s o l u t e showing the greatest degree of d i s -s o c i a t i o n . Moreover at very high concentrations CofPOgFg^ shows the g r e a t e s t decrease i n W c o n s i s t e n t w i t h i t being the l e a s t d i s s o c i a t e d . The i n t e r p r e t a t i o n of the c o n d u c t i v i t y data on the b a s i s of model ( i i ) appears to be the more reasonable of the two model proposed i . e . i o n a s s o c i a t i o n i n HPO2F2 i s important and metal difluorophosphates are weakly d i s s o c i a t e d i n t h i s s o l v e n t . Further evidence supporting t h i s c o n c l u s i o n was obtained from t h n.m.r., v i s c o s i t y and d e n s i t y s t u d i e s to be discussed l a t e r i n t h i s chapter and a l s o from the f a c t that tetraphenylarsonium c h l o r i d e gives more h i g h l y conducting s o l u t i o n s than the metal difluorophosphates (to be presented i n Chapter I I I ) . B) Nuclear magnetic resonance The -^H, 1 9 F , and chemical s h i f t s of the s o l v e n t peak r e l a t i v e to an e x t e r n a l r e f e r e n c e of HPOoFp were measured f o r a number of s o l u t i o n s of a l k a l i metal s a l t s i n HPO^Fg. The r e s u l t s are given i n Table 5 and the uncorrected values are p l o t t e d against the molal c o n c e n t r a t i o n i n F i g s . 7 -9 . The chemical s h i f t s were measured f o r s o l u t i o n s over the same co n c e n t r a t i o n range as t h a t used i n c o n d u c t i v i t y measurements and as a r e s u l t the s h i f t s are very s m a l l and correspondingly very s e n s i t i v e t o i m p u r i t i e s such as water and p a r t i c u l a r l y paramagnetic species. I n s p i t e of these d i f f i c u l t i e s reasonably smooth curves x^ere ob-t a i n e d f o r a l l the s o l u t e s s t u d i e d except the resonance of K P 0 2 F 2 s o l u t i o n s . This s a l t showed the smallest dependence of "Hi chemical s h i f t on c o n c e n t r a t i o n and gave r e s u l t s which were very s c a t t e r e d and d i f f i c u l t to reproduce. Chemical s h i f t s are observed f o r a l l three n u c l e i when s a l t i s added and the nature of the s h i f t depends on the a l k a l i metal. The s h i f t s were c o r r e c t e d f o r bulk diamagnetic suscep-t i b i l i t y e f f e c t s according to the equation 1*', S = H-H r e f . + 2_TT ( X w ^ e f . — > X i r ) H r e f . 3 v The s u s c e p t i b i l i t i e s of the s o l u t i o n s x^ere c a l c u l a t e d from P a s c a l constants and the Wiedmann mixture law. The molar diamagnetic s u s c e p t i b i l i t y of d i f l u o r o p h o s p h o r i c a c i d was taken as 38 x 10 ^c.gs.; t h i s value was estimated by u s i n g t h a t of ortho-phosphoric a c i d (43.8 x 10~^c.gs.)^ and s u b s t i t u t i n g two f l u o r i n e 9.1 x 10""6 c,g S.) f o r two hydroxyl groups (12.0 x 10""^c.gs.) .•^ 1 C o r r e c t i o n s f o r the bulk diamagnetic s u s c e p t i b i l i t y e f f e c t s were estimated and are given i n Table 5. The a p p l i c a t i o n of these cor r e c t i o n s does not a l t e r the nature of the r e s u l t s obtained; the TABLE 5 •^H, 1 < 7F and 3 1 P Chemical S h i f t s * f o r S o l u t i o n s of MP0 2F 2 i n HP0 2F 2 1 0 2 m . H 6.792 +0 .0142(.0010) 17.06 +0.0418( .0030) 27.90 +0.0620( .0031) 32.59 +0.0756(.0025) 50.44 + 0 . 0 9 0 8 ( . 0 0 2 1 ) 6 . 5 0 3 +0.0175(.0006) 12.2,7 + 0 . 0 2 4 0( .0018) 2 8 . 3 9 +O.O415 (.0030) 3 1 . 8 5 + 0 . 0 4 7 9 ( . 0 0 2 0 ) 4 7 . 7 9 + 0 . 0 5 5 9 ( . 0 0 2 0 ) Chemical S h i f t (p.p.m.) 19W L i P 0 2 F 2 -0.0627(.0002) -0.133 (.001) -0.191 (.001) -0.224 (.002) -0.311 (.001) NaP0 2F 2 -0.0788(.OO64) -0.138 ( .007) -0.288 (.004) -0.316 ( .004) -0.442 ( .004) KP0 2F 2 31T Suscept. c o r r (p.p.m.) - 0 . 0 5 4 6 ( . 0 0 4 9 ) -O.I46 ( . 0 0 5 ) - 0 . 2 0 7 ( . 0 1 7 ) - 0 . 2 5 9 ( . 0 0 6 ) - 0 . 3 8 3 ( . 0 0 5 ) - 0 . 0 7 7 6 ( . 0 0 7 4 ) -0 .165 ( . 0 1 0 ) -0.413 ( . 0 1 2 ) - 0 . 4 4 7 ( . 0 1 5 ) - 0 . 6 7 0 ).017) + 0 . 0 0 1 + 0 . 0 0 4 + 0 . 0 0 8 + 0 . 0 1 0 +0.016 +0.003 +0.006 +0.014 +0.017 +0.025 9 .030 +0.0282( .0010) - 0 . 0 8 3 9 ( . 0 0 5 3 ) -0.124 ( .008) +0.007 1 7 . 4 2 - 0 . 0 1 9 ( .002) -O.I84 ( .003) - 0 . 2 3 6 ( .003) +0.013 2 5 . 6 2 +0.026 ( .002) - 0 . 2 0 7 ( .004) - 0 . 2 9 4 ( .011) +0.018 3 5 . 8 4 - 0 . 0 2 9 ( .002) - 0 . 3 6 9 (.005) - 0 . 4 6 9 ( .005) +0.029 4 5 . 4 2 -0 .455 (.005) -0.531 ( .015) +O.O35 NH 4 P 0 2F 2 8.633 -0.0144(0012) - 0 . 0 9 9 9 ( . 0 0 0 3 ) -0.0588( .0015) +0.008 14 .89 -0.0144( .0006) -0 .156 (.003) -0.114 ( .0005) +0.014 32.73 -0.0679( .0002) - 0 . 3 5 1 (.005) - 0 . 2 7 7 ( .008 +0.033 34.74 -0.0725( .0002) -O.366 (.004) -O.304 ( .002) +0.035 56.03 -O.132 ( .001) -0 .553 (.010) -0.LS2 (.013 R b P 0 2F 2 5'.040 .0023) - 0 . 0 6 6 7 ( . 0 0 0 7 ) -0.0596( .0035 +0.004 15.50 -0.0276( -O.I9O ( .003) +0.014 21.97 - 0 . 0 4 3 2 ( . 0 0 0 5 ) - 0 . 2 7 1 ( .004) - 0 . 2 6 9 ( .005) +0.022 32.47 -0.0790( .0021) - 0 . 3 9 1 (.005) - 0 . 4 1 0 ( .008) +0.032 37.74 -0.0946( .0030 - 0 . 4 4 3 (.005) -O.472 ( .011) +0.038 33 TABLE 5 (cont'd) 2 10 in Chemical S h i f t (p.p.m.) Suscept. c o r r . C s P 0 2 F 2 1 1 . 8 9 - 0.0132( . 0 0 0 4 ) - 0 . 1 5 2 ( . 0 0 3 ) - 0 . 1 5 7 ( . 0 0 4 ) +0.017 14 . 7 0 - 0 . 0 2 5 3 (.0012) -0.190(.002) - 0.180 ( . 0 0 3 ) +0.021 20 . 7 5 -0.0781(.0010) - 0.273 ( . 0 0 4 ) - 0 . 2 5 9(.011) + 0 . 0 3 0 3 2 . 6 2 -0.127 (.002) - 0 . 4 2 8 ( . 0 0 5 ) - 0 . 4 0 8(.010) +O.O49 43 . 8 6 -O . I64 (.006) - 0 . 5 1 7 ( . 0 0 5 ) +0.066 * Values f o r the s h i f t s are the average values of at l e a s t two • determinations; the values i n the brackets are the average d e v i a t i o n s . 36 c o r r e c t i o n s simply s h i f t . t h e curves s l i g h t l y t o higher f i e l d s and so f o r d i s c u s s i o n purposes the uncorrected curves, shown i n F i g s . 7-9 only need be considered. The e f f e c t on the solvent proton chemical s h i f t of adding s a l t s has been i n v e s t i g a t e d i n a number of s o l v e n t s , notably H 2 0 ^ 2 , H 2 S 0 4 -^and HSO^F"^. I n a s e r i e s of compounds s t u d i e d by Schneider, B e r n s t e i n and Pople-^ i t was found that i n a l l cases a s s o c i a t i o n through hydrogen bonding s h i f t s the proton s i g n a l to low f i e l d . A s s o c i a t i o n through hydrogen bonding w i l l thus pro-duce a l o w - f i e l d s h i f t whereas h i g h - f i e l d s h i f t s caused by s o l -vated i o n s can be a t t r i b u t e d to there being fewer hydrogen bonds between the s o l v a t i o n l a y e r and the bulk solvent than between the s o l v e n t molecules themselves. This break-up of solvent s t r u c t u r e has been examined e x t e n s i v e l y i n water by proton mag- • n e t i c resonance-^ 2. Hindman^ D d i v i d e d the e f f e c t s of ions on the proton magnetic s h i e l d i n g by e l e c t r o n s i n water molecules to h i g h - and l o w - f i e l d s h i f t s . The h i g h - f i e l d s h i f t s were a t -t r i b u t e d to the breaking of hydrogen bonds i n the process of r e -o r i e n t a t i n g the water molecules by the i o n , r e l a t e d to the forma-t i o n of the primary s o l v a t i o n l a y e r , and a l s o the breaking of a d d i t i o n a l bonds beyond the primary h y d r a t i o n l a y e r i . e . i n the i n the s t r u c t u r e broken r e g i o n . I f an: i o n were capable of i n -ducing more hydrogen bonding i n the s o l u t i o n than e x i s t e d i n the pure s o l v e n t a l o w - f i e l d s h i f t would occur. Before proceeding with' a d i s c u s s i o n of the r e s u l t s ob-t a i n e d i n t h i s work, i t i s convenient t o consider the r e s u l t s of analogous 1H n.m.r. s t u d i e s by other workers on s o l u t i o n s of 3 8 a l k a l i metal hydrogen sulphates i n s u l p h u r i c a c i d and a l k a l i metal f l u o r o s u l p h a t e s i n f l u o r o s u l p h u r i c acid^*". I n both cases i t was observed t h a t a d d i t i o n of s a l t caused the sol v e n t proton s i g n a l t o s h i f t to l o w - f i e l d s . The extent of t h i s s h i f t de-pended on the co n c e n t r a t i o n of the s a l t and the a l k a l i metal c a t i o n i n v o l v e d — the l a r g e s t l o w - f i e l d s h i f t being produced by the l a r g e s t c a t i o n . These r e s u l t s were explained as f o l l o w s : The anion (SCUF~ i n the case of HSO-F s o l u t i o n s and HSO, ~ i n } 3 4 the case of H 2 S °4 s o l u t i o n s ) i n t e r a c t s w i t h the so l v e n t molecules i n such a -way as to in c r e a s e the number of hydrogen bonds present i n s o l u t i o n over t h a t o c c u r r i n g i n the pure s o l v e n t and hence causes a s h i f t to l o w - f i e l d . Superimposed on t h i s i s the e f f e c t of the c a t i o n which by v i r t u e of i t s s o l v a t i o n breaks up the sol v e n t s t r u c t u r e and so decreases the number of hydrogen bonds-present and thus gives r i s e to a h i g h - f i e l d s h i f t i n the proton resonance. The s m a l l e r the c a t i o n the greater i s i t s degree of 3 7 s o l v a t i o n and the gr e a t e r i s the u p - f i e l d s h i f t caused by i t . The o v e r a l l downfield s h i f t observed f o r a l l the s a l t s i s due t o the f a c t t h a t the e f f e c t of the anion i s c o n s i d e r a b l y greater than t h a t of the c a t i o n . The r e s u l t s of the present s t u d i e s on a l k a l i metal d i -fluorophosphates d i s s o l v e d i n HPO2F2 are t o be cont r a s t e d w i t h those described above. L i t h i u m and sodium difluorophosphate a c t u a l l y cause a s h i f t to h i g h - f i e l d i n the proton resonance of the s o l v e n t w h i l e rubidium and cesium difluorophosphate cause a s h i f t to l o w - f i e l d . I t would appear th a t u n l i k e the s i t u a t i o n w i t h K^ SO^ , and HSO^F the down-field s h i f t caused by the anion i s 39 of comparable magnitude to the u p - f i e l d s h i f t caused by the c a t i o n s . I t i s important to note, however, t h a t as i n the previous systems s t u d i e d , HSO^F and H^SO^, the s m a l l e r the c a t i o n the greater i s the s h i f t t o h i g h - f i e l d , suggesting t h a t i n HPO^Fg the c a t i o n s are s o l v a t e d , the s m a l l e r ones being more s o l v a t e d than the l a r g e r ones. The. problem which remains i s d i s c o v e r i n g why the P(02^2~ i o n does not cause a l a r g e s o l v e n t proton s h i f t to low-f i e l d s as do the HS0^~ and SO^F" i o n s i n t h e i r r e s p e c t i v e s o l -vents. The answer probably l i e s i n the f a c t t h a t the metal d i -fluorophosphates are e x t e n s i v e l y i o n - p a i r e d i n HPO^F^. The a l k a l i metal c a t i o n s may be p i c t u r e d as being s o l v a t e d by s o l -vent molecules w i t h difluorophosphate anions present w i t h i n the c a t i o n s o l v a t i o n s h e l l . Hence the c a t i o n s by v i r t u e of t h e i r s o l v a t i o n cause an u p - f i e l d s h i f t i n the ~*"H resonance w h i l e the P0 2F 2"" i o n s have l e s s e f f e c t on the solvent chemical s h i f t than they would i f they were f r e e ions as i s the case f o r HSO^- ions i n H o S 0 , and SO_F~ i o n s i n HSCLF. When a l k a l i metal difluorophosphates are added to HPO2F2 a s i n g l e ^9p resonance i s observed ( a c t u a l l y a doublet due to c o u p l i n g w i t h phosphorusf^which i s an average s i g n a l due to f l u o r i n e atoms i n the solvent molecules and f l u o r i n e atoms i n the P O 2 F 2 " i o n s . The s h i f t of t h i s s i g n a l w i t h respect t o pure HPOgFg was measured f o r a number of s o l u t i o n s and the r e s u l t s are presented g r a p h i c a l l y i n F i g . 8 . Due t o the f a c t t h a t POgFg" in i s an anion i t would be expected t h a t the 7 F resonance would occur at higher f i e l d s trengths than the "^p resonance of HPO2F2 and. hence the a d d i t i o n of M P 0 2 F 2 t o HPOgFg might be expected to 4 0 cause a F u p f i e l d s h i f t r e l a t i v e t o pure HPO2F2. However, as can be seen i n F i g . 8, a l l of the s h i f t s are to l o w - f i e l d . I n analogous s t u d i e s on s o l u t i o n s i n f l u o r o s u l p h u r i c a c i d i t was found t h a t the 1 9 F resonance i s indeed s h i f t e d t o high f i e l d as metal f l u o r o s u l p h a t e s are added to the s o l v e n t . Again i t i s concluded t h a t the expected h i g h - f i e l d s h i f t due to added POgFg" i o n s to d i f l u o r o p h o s p h o r i c a c i d i s not observed because the ^®2^2~ i ° n s a r e n o t ' f r e e * but are present i n the s o l v a t i o n sphere of the c a t i o n . The down-field s h i f t s which are observed are presumably due t o the i n t e r a c t i o n of the c a t i o n s w i t h the s o l v e n t molecules. I t i s i n t e r e s t i n g to note t h a t the l a r g e s t down-field s h i f t i s observed f o r the l a r g e s t c a t i o n , C s + , v' which has the most sol v e n t molecules i n the f i r s t s o l v a t i o n sphere and hence i n the immediate environment of the c a t i o n . 31 The P n.m.r. s t u d i e s of s o l u t i o n s of a l k a l i metal d i -fluorophosphates i n HPO2F2 show, as was the case f o r the 1 9 F s p e c t r a , that added metal difluorophosphate s h i f t s the "average" resonance to l o w - f i e l d s . Again, the expected h i g h - f i e l d s h i f t due t o the added P 0 2 F 2 ~ i o n s i s n o t observed and the dov/nfield s h i f t s are presumably due to the i n t e r a c t i o n of the solvent mole-1 19 cu l e s w i t h the c a t i o n s . U n l i k e the H and F n.m.r. r e s u l t s there i s no c o r r e l a t i o n between the magnitude of the observed s h i f t and the s i z e of the a l k a l i metal c a t i o n although L i + does seem to show a s i g n i f i c a n t l y s maller downfield s h i f t than the other c a t i o n s and t h i s i s probably due to the f a c t t h a t there are fewer solvent molecules i n i t s f i r s t s o l v a t i o n sphere. I t i s t o be expected that the c a t i o n - s o l v e n t i n t e r a c t i o n s w i l l have l e s s 41 e f f e c t on the s h i e l d i n g constant of the P nucleus than on the H or F n u c l e i s i n c e the phosphorus atom i s p o s i t i o n e d at the centre of the molecule, screened by two f l u o r i n e atoms and two oxygen atoms from the c a t i o n . This probably accounts f o r the f a c t t h a t l i t t l e d i f f e r e n c e i s observed i n the p l o t s i n F i g . 9 f o r the Na, K, Rb and Cs s a l t s . 2 . 3 C) D e n s i t i e s fluorophosphate s o l u t i o n s i n d i f l u o r o p h o s p h o r i c a c i d at 25 are g i v e n and i n F i g . 10 the d e n s i t i e s of these s o l u t i o n s are p l o t t e d against c o n c e n t r a t i o n , m, expressed i n moles per lOOOg. of s o l v e n t . I t appears t h a t i n o r g a n i c c a t i o n s cause an increase c e n t r a t i o n . G i l l e s p i e and W a s i f p found a s i m i l a r t r e n d f o r metal b i s u l p h a t e s i n s u l p h u r i c a c i d but a decrease i n d e n s i t y w i t h i n c r e a s i n g c o n c e n t r a t i o n was observed f o r organic c a t i o n s . Density changes can be more conveniently discussed i n terms of the apparent molar volume of the s o l u t e s r a t h e r than i n terms of the d e n s i t i e s themselves. The molar volume, 0, of an e l e c t r o -3 l y t e i s r e l a t e d t o the d e n s i t y of the s o l u t i o n , d, by the equation, the pure so l v e n t and m, the m o l a l i t y of the s o l u t i o n . The apparent molar volumes given i n Table 6b v;ere c a l -c u l a t e d from the equation. I t can be seen that there i s no marked change i n the apparent molar volume w i t h c o n c e n t r a t i o n and I n Table 6 the d e n s i t i e s , d, of some a l k a l i metal d i -TABLE 6 a) D e n s i t i e s and V i s c o s i t i e s of Some Solutes i n HPO2F2 at 25 L i P 0 2 F 2 102m D 5^ ^ 0 0.000 1.5827 (.0001) 5.200 (.040) 7.185 1.5855 (.0002) 4.544 (.040) 48.9 18.29 1.5911 (.0003) 4.392 (.018) 48.2 23.36 1.5965 (.0002) 4.330 (.055) 48.7 32.30 1.5984 (.0005) 4.350 (.075) 47.8 RbP0 2F 2 " 0.000 5.200 (.040) 10.06 1.6003 (.0004) 4.536 (.030) 45.0 22.07 1.6197 (.0005) 4.366 (.090) 48.0 35.45 1.6413 (.0003) 4.310 (.193) 48.0 K P 02 F 2 0.000 1.5824 ( .0002) 5.769 ( .001) 12.60 1.5960 (.0004) 5.122 ( .020) 44-0 23.54 I .6O64 (.0001) 5.029 ( .018) 47.0 39.16 1.6231 (.0003) 4.306 ( .021) 45.6 54.49 I .638O (.0008) 4.617 (.040) 45.3 Ba(P0 2F 2)2 0.000 5.722 ( .020) 13.57 5.011 (.131) 23.05 1.6406 ( .0008) 5.269 (.065) H O 29.95 1.6599 (.0005) 5.407 ( .055) 106 (CH 0),NC1 3 4 0.000 5.658 (.052) 16.45 3.963 (.025) 27.34 1.5745 (.0011) 3.724 (.035) 49.52 1.5699 ( .0012) 2.900 (.015) o TABLE 6 (cont'd) b) Solute Mean 0 mis. Mean 0^ mis. M e a n $H2S0k L i P 0 2 F 2 48 t l -16 t l -7.0 K P 0 2 F 2 45 -2 -19 t 2 -1.0 RbP0 2F 2 47 ±2 -17 -2 +5.0 B a ( P 0 2 F 2 ) 2 108 t2 -20 t 2 -12 c) v i s c o s i t y depression,AT\ 0 • m o l a l i t y , 10S i . Solute 0.100 0.200 0 .300 L i P O j ^ -0 .707 -0.804 -0 .847 K P 0 2 F 2 -0.519 -0.888 -1.27 RbP0 2F 2 -0 .655 -0.820 -0 .869 B a ( P 0 2 F 2 ) 2 -0 .637 -0.642 -0.222 ( C H j N C l J 4 -1 .09 -1 .83 -2.29 - 7 . 0 +1.7 +7.7 -24.3 0.400 - 0 . 8 7 2 -I . 4 6 - 0 . 8 9 0 - 2 . 5 6 45 a l s o the apparent molar volumes are v i r t u a l l y the same f o r a l l of the a l k a l i metal s a l t s s t u d i e d . This i s to be co n t r a s t e d w i t h the r e s u l t s obtained f o r s o l u t i o n s i n H SO.^ and Ho0^"^ 2 i f 2 where the apparent molar volume i s a f u n c t i o n of the concentra-t i o n and nature of the s a l t added. I n the water and HgSO^ work values of 0*, the apparent molar volume of the c a t i o n s , were c a l c u l a t e d assuming t h a t the p a r t i a l molar volumes of the anions are the same as the molar volumes of the solvent molecules. I f i t i s assumed th a t the apparent molar volume occupied by a difluorophosphate i o n i n s o l u t i o n i s the same as tha t of a d i f l u o r o p h o s p h o r i c a c i d molecule, then 0^ values may be obtained. The values given i n column 3 of Table 6b were c a l c u l a t e d by us i n g a f i g u r e of 64 mis., the molar volume of HPO2F2, f o r the apparent molar volume of the difluorophosphate i o n . Thus the apparent molar volume of the c a t i o n , 0*, i s given by: 0 - 64 = 0*. These are compared w i t h the apparent molar volumes i n aqueous s o l u t i o n and i n s u l p h u r i c a c i d and as can be seen the values are co n s i d e r a b l y greater i n the case of HPO2F2 s o l u t i o n s . I t seems l i k e l y t h a t the 0^ values i n d i f l u o r o p h o s p h o r i c a c i d are i n -c o r r e c t . I f a p a r t i a l molar volume of l e s s than 64 i s assumed f o r the d i f luorophosphate anion then the values of 0"*" w i l l be i n b e t t e r agreement w i t h those obtained i n the other systems. I n -deed, i f the difluorophosphate anions are present i n the s o l v a t i o n spheres of the c a t i o n s and not ' f r e e ' , as i t i s s t r o n g l y suspec-t e d , then i t i s not unreasonable to expect t h a t the anion w i l l have a s m a l l e r apparent molar volume than the sol v e n t molecules. 19 32 I t has been shown that i n s u l p h u r i c a c i d • and water 46 the extent of s o l v a t i o n of metal c a t i o n s decreases i n the order B a ^ L i ^ K^Rb. From Table 6b i t can be seen th a t t h i s same order p r e v a i l s w i t h i n c r e a s i n g negative values of i . e . B a 2 + i s most negative and Rb + most p o s i t i v e . The values f o r the d i f l u o r o -phosphates are approximately the same and thus no i n f o r m a t i o n r e g a r d i n g the r e l a t i v e order of s o l v a t i o n numbers can be ob-t a i n e d as was p o s s i b l e i n the s o l v e n t s where the s a l t s were f u l l y d i s s o c i a t e d . 2.3 D) V i s c o s i t i e s I n Table 6a the v i s c o s i t i e s f o r various s o l u t i o n s are given. The e f f e c t of the s o l u t e on the v i s c o s i t y i s given by, " l^o w n e r e I s t n e v i s c o s i t y of the s o l u t i o n . I n t e r p o l a t e d values are given i n Table 6c f o r the v i s c o s i t y depression. A l l the s o l u t e s s t u d i e d caused a decrease i n the v i s c o s i t y w i t h tetramethylammonium c h l o r i d e causing the l a r g e s t depression. 38 I n s u l p h u r i c a c i d i t was found that metal hydrogen sulphates g e n e r a l l y cause an in c r e a s e i n the v i s c o s i t y , the e f -f e c t of the a l k a l i n e earths being p a r t i c u l a r l y g r e a t , whereas organic molecules were found to cause a sm a l l decrease i n the v i s c o s i t y . G i l l e s p i e e xplained changes i n the v i s c o s i t y i n terms of the e f f e c t s of the c a t i o n s on the s t r u c t u r e of the so l v e n t . The s m a l l i n o r g a n i c c a t i o n s were considered to cause a ' t i g h t e n -i n g 1 of the s t r u c t u r e of the solvent around the i o n , p u l l i n g the solv e n t molecules s t r o n g l y together and considerably r e s t r i c t -i n g t h e i r freedom of movement and thus i n c r e a s i n g the v i s c o s i t y . However, i n the case of the .large organic c a t i o n s i t was suggested th a t i n a d d i t i o n to the e f f e c t caused by t h e i r s o l v a t i o n the bulky 47 groups would tend to d i s r u p t the s t r u c t u r e of the surrounding s o l v e n t , as they would not f i t e a s i l y i n t o i t and t h i s would probably be accompanied by a decrease i n v i s c o s i t y . The v i s c o s i t i e s of a l l the d i f l u o r o p h o s p h o r i c a c i d s o l u t i o n s are l e s s than the v i s c o s i t y of pure HPO2F2, thus i n d i c a t -i n g the behaviour of l a r g e , bulky s o l u t e s and not of f u l l y d i s -s o c i a t e d s a l t s . I t may be that the i o n p a i r i t s e l f i s s t r u c t u r e breaking and would not e a s i l y f i t i n t o the s t r u c t u r e of the sur-rounding s o l v e n t . V i s c o s i t y and d e n s i t y measurements were a l s o made on tetramethylammonium c h l o r i d e s o l u t i o n s i n HPO2F2 as a comparison study. CHAPTER I I I Miscellaneous Bases A) Organic Bases 3 . 1 I n t r o d u c t i o n A l a r g e number of organic compounds are bases i n the 20 21 hydrogen f l u o r i d e and s u l p h u r i c a c i d ' solvent systems. Most substances c o n t a i n i n g oxygen, n i t r o g e n or sulphur atoms t h a t are not c o o r d i n a t i v e l y s a t u r a t e d o f f e r a lone e l e c t r o n p a i r capable of b i n d i n g protons i n a c i d i c s o l v e n t s . I n HgSO^ amines are strong bases and are simply converted to t h e i r conjugate a c i d s 1 9 . Nitrocompounds, however, being weaker bases, e x h i b i t a v a r i e t y of base strengths (m-nitrotoluene> nitrobenzene y p - n i t r o c h l o r o b e n z e n e ^ 2,4-dinitrotoluene) and are not f u l l y protonated. I t was of i n t e r e s t to see whether a span of base strengths of such organic molecules can be observed i n HPO^Fg s o l u t i o n s . 3 . 2 Experimental A) E l e c t r i c a l c o n d u c t i v i t y s t u d i e s were c a r r i e d out at 25° on s o l u t i o n s of various organic bases i n the c e l l shown i n Fig.. 2. The procedure adopted was the same as that o u t l i n e d p r e v i o u s l y ; s o l i d s were added by means of the ' i n j e c t o r 1 and l i q u i d s by the microburette. B) P r e p a r a t i o n and p u r i f i c a t i o n of m a t e r i a l s Nitrobenzene: 'Analar* nitrobenzene was p u r i f i e d by f r a c t i o n a l f r e e z i n g followed by d o u b l e - d i s t i l l a t i o n under vacuo. Benzoic a c i d : 'Analar' grade benzoic a c i d was r e c r y s -t a l l i z e d from water and d r i e d over phosphoric oxide i n a vacuum 49 d e s i c c a t o r . O x a l i c a c i d : l A n a l a r * grade o x a l i c a c i d was d r i e d i n an oven at 150° and st o r e d over phosphoric oxide i n a vacuum d e s i c -c a t o r . Reagent grade 2 , 4 - d i n i t r o t o l u e n e , p - n i t r o t o l u e n e , m - n i t r o a n i l i n e , p - n i t r o a n i l i n e , p-nitrochlorobenzene and p-dinitrobenzene were r e c r y s t a l l i z e d from methanol, d r i e d and stor e d over phosphoric oxide i n a vacuum d e s i c c a t o r . 3.3 R e s u l t s and d i s c u s s i o n The r e s u l t s of the c o n d u c t i v i t y measurements on s o l u t i o n s of p - n i t r o a n i l i n e , m - n i t r o a n i l i n e , 3 , 4 - d i c h l o r o a n i l i n e , 2 , 4 - d i n i t r o t o l u e n e , p - n i t r o t o l u e n e , p-nitrochlorobenzene, p-dinitrobenzene, nitrobenzene, benzoic a c i d and o x a l i c a c i d are given i n Table 7 and are p l o t t e d against the m o l a l i t y of the s o l u t i o n i n F i g . 11. I t was found th a t the a n i l i n e s and benzoic a c i d were completely s o l u b l e over the con c e n t r a t i o n range s t u d i e d whereas o x a l i c a c i d , p-dinitrobenzene and 2 , 4 - d i n i t r o t o l u e n e ap-peared v i r t u a l l y i n s o l u b l e and caused e s s e n t i a l l y no change i n the c o n d u c t i v i t y when added to HP02F2. Assuming t h a t the point at which f u r t h e r a d d i t i o n of s o l u t e causes no n o t i c e a b l e increase i n the c o n d u c t i v i t y of the s o l u t i o n corresponds at l e a s t a p p r o x i -mately t o the s o l u b i l i t y of the s o l u t e i t would appear th a t the compounds p - n i t r o t o l u e n e , p-nitrochlorobenzene and nitrobenzene have s o l u b i l i t i e s 0 .08, 0.034 and 0.15 moles/kg. r e s p e c t i v e l y . The three a n i l i n e s have n e a r l y l i n e a r c o n d u c t i v i t y -m o l a l i t y curves which are s i m i l a r , p a r t i c u l a r l y at low concentra-t i o n s , t o the curve obtained f o r cesium difluorophosphate. This TABLE 7 Conductivities of Some Organic Bases i n Difluorophosphoric Acid at 25° p - n i t r o a n i l i n e m-nitroanlline 102m. 104X' 102m. 10*X ohrrT+cm. ohm_1crn. 0.0000 2.435 0.0000 2.648 0.2666 2.489 0.8946 2.538 1.218 2.836 3.256 3.456 2.576 3.457 7.252 5.273 4.562 4.366 12.34 7.467 7.304 5.583 19.60 10:73. 10.30 6.849 27.41 13.63 14.51 8.542 35.85 17.58 18.56 10.11 43.64 19.78 22.87 12.67 50.75 21.53 2 , 4-dinitrotoluene p-nitrotoluene 0.0000 2.417 0.0000 2.458 0.7450 2.476 0.8714 2.688 1.932 2.474 2.377 3.325 4.267 2.456 4.638 4.233 insoluble 7.969 4.896 12.88. . 4.851 insoluble nitrobenzene p-dinitrobenzene 0.0000 2.893 0.2224 2.962 0.0000 2.885 0.5004 3.057 0.6382 2.940 0.9823 3.228 4.565 2.945 1.909 3.534 insoluble 3.077 3.912 4.374 4.331 oxalic acid 6.635 4-982 Q.0000 2.690 9.434 5.752 13.12 6.679 insoluble 16.83 6.845 insoluble 3,4-dichloroaniline 1 102m. 1 0 ^ ohm^cm 0.0000 2.569 0.4074 2.483 1.156 2.596 2.843 3.227 5-493 4.339 8.738 5.630 12.50 7.039 16.97 8.635 21.04 10.03 25.30 11.62 p-nitrochlorobenzi 0.0000 2.617 0.5345 2.699 1.711 2.850 3.380 2.892 6.O64 2.804 insoluble benzoic acid 0.0000 2.458 0.4769 2.602 1.406 2.895 3.207 3.440 5.947 4.186 9.825 5.101 14.05 5.966 19.82 6.993 24.40 7.682 27.10 8.074 -1 F i g . 11 S p e c i f i c C o n d u c t i v i t i e s of Some Organic Bases i n HPO^F^ at 25° r • © CsP0 2F 2 A p - n i t r o a n i l i n e • m - n i t r o a n i l i n e O 3 , h , - d i c h l o r o a n i l i n ^ H nitrobenzene O benzoic a c i d 0 io io2 x m o l a l i t y , m 52 suggests they are f u l l y protonated but, l i k e the metal d i f l u o r o -p'hosphates, are a l s o i n c o m p l e t e l y d i s s o c i a t e d . I t i s not s u r -p r i s i n g t h a t the degrees of d i s s o c i a t i o n f o r the a n i l i n e s are s i m i l a r i n view of a g e n e r a l s i m i l a r i t y , i n the s i z e s of the c a t i o n s of the i o n p a i r s , v i z . RM^'PC^Fp -. G i l l e s p i e et a l . 1 ^ have compared the i o n i z a t i o n constants f o r some n i t r o compounds i n f l u o r o s u l p h u r i c and s u l p h u r i c a c i d s and due to the greater a c i d i t y of HSO^F organic bases are i n general protonated to a g r e a t e r extent i n t h i s s o l v e n t . I t -was found t h a t the i o n i z a t i o n constants decreased i n the order n i t r o b e n z e n e ^ p-nitrochlorobenzene/> 2 , 4 ~ d i n i t r o t o l u e n e ; benzoic a c i d was f u l l y i o n i z e d i n HSO^F and H^SO^. I t would be expected, t h e r e f o r e , as d i f l u o r o p h o s p h o r i c a c i d i s known to be a weaker 2 ? a c i d than H^SO^ t h a t the extent of d i s s o c i a t i o n of organic s o l u t e s w i l l be much l e s s . The n i t r o compounds were i n f a c t found to be l e s s s o l u b l e i n HPO2F2 than the amines,with . the -strongest bases nitrobenzene and p - n i t r o t o l u e n e , showing the g r e a t e s t s o l u b i l i t y . This l a c k i n s o l u b i l i t y on the p a r t of the n i t r o compounds i s c o n s i s t e n t w i t h them being weaker bases than the amines. The b a s i c i t y of an organic s o l u t e r e l a t i v e t o the solvent must be great enough to at l e a s t cause hydrogen bonding w i t h the s o l v e n t , otherwise i t i s u n l i k e l y to be able t o s u f -f i c i e n t l y d i s r u p t the s t r u c t u r e of the solvent t o enable i t to d i s s o l v e . The f o r m a t i o n of the conjugate a c i d from an organic base can be considered as a two-step process: 53 B + HP0 2F 2 ^ HB'T ,0 2F 2~ (3 .1 ) HB J rP0 2F 2- ^ HB + + P 0 2 F 2 ~ (3 .2 ) the f i r s t step being the p r o t o n a t i o n of the base to form an i o n - p a i r and the second step being the d i s s o c i a t i o n of t h i s species i n t o f r e e i o n s . I t i s probable t h a t , i n the case of benzoic a c i d , the lower c o n d u c t i v i t i e s r e l a t i v e to those observed f o r the organic amines are due t o incomplete p r o t o n a t i o n , i . e . the benzoic a c i d i s a weaker base than the amines and hence step (3 .1 ) does not go to completion. B) Inorganic Solutes 3 . 4 I n t r o d u c t i o n I t i s w e l l known t h a t i n s u l p h u r i c a c i d " ^ the a l k a l i and some other metal hydrogen sulphates behave as strong bases, analogous to hydroxides i n water. Many s a l t s of other f a m i l i a r i n o r g a n i c a c i d s undergo complete s o l v o l y s i s as i s i l l u s t r a t e d i n the f o l l o w i n g examples, KNO3 + H 2 S 0 ^ - K + + HSO^' + HNO3 NH^CIO^ + H 2S0 4 = NH 4 + + HSO^" + HCIO^ As the a l k a l i and a l k a l i n e e a r t h metal difluorophosphates were prepared from the corresponding c h l o r i d e s i t was of i n t e r e s t to disc o v e r whether complete s o l v o l y s i s of the c h l o r i d e s takes place i n s o l u t i o n . I n an e f f o r t t o examine the general usefulness of e l e c t r i c a l c o n d u c t i v i t y s t u d i e s i n determining modes of r e -a c t i o n of s o l u t e s i n d i f l u o r o p h o s p h o r i c a c i d , c o n d u c t i v i t y measurements were made of s o l u t i o n s of potassium n i t r a t e and 54 carbonate i n ll?O^F^. 3.5 Experimental E l e c t r i c a l c o n d u c t i v i t y s t u d i e s were c a r r i e d out at 25° on s o l u t i o n s of v a r i o u s i n o r g a n i c s o l u t e s i n the c e l l shown i n F i g . 2. The s o l u t e s were added by means of the " i n j e c t o r " as described p r e v i o u s l y . Tetraphenylarsonium c h l o r i d e : commercial t e t r a p h e n y l -arsonium c h l o r i d e obtained from A l d r i c h Chemical Co. was d r i e d i n . a d r y i n g p i s t o l c o n t a i n i n g phosphoric oxide at 100° and 15 mms. pressure. Tetramethylammonium c h l o r i d e : commercial grade obtained from Matheson Co. Inc. was r e c r y s t a l l i z e d from ethanol and d r i e d by heating under vacuo. The a l k a l i earth and a l k a l i metal c h l o r i d e s were d r i e d by heating t o 190° i n an oven' f o r 18 hours and then stored over phosphoric.oxide i n a vacuum d e s i c c a t o r . 3 . 6 R e s u l t s and. D i s c u s s i o n I n Table 8 the e l e c t r i c a l c o n d u c t i v i t y values f o r v a r i o u s a l k a l i and a l k a l i n e earth metal c h l o r i d e s o l u t i o n s i n HPO2F2 are given and they are p l o t t e d against the c o n c e n t r a t i o n expres-sed as a m o l a l i t y i n F i g . 12. Included i n the f i g u r e are the e l e c t r i c a l c o n d u c t i v i t y curves f o r the corresponding d i f l u o r o -phosphates (shown as a s o l i d l i n e ) and as can be seen the conduc-t i v i t y curves f o r the difluorophosphates at low concentrations are v i r t u a l l y i d e n t i c a l w i t h the experimental p o i n t s of the c h l o r i d e s . However, at high concentrations some d e v i a t i o n I s TABLE 8 S p e c i f i c Conductances of Some Inorganic E l e c t r o l y t e s i n Difluorophosphoric A c i d at 25° KC1 NaCl C a C l 2 102m. lO^X 102m. l O ^ 102m. lO^ X ohm~lcm7-'- ohm -lcm.-i ohm**lcm. 0.000 2 .780 0 .000 2.789 0.000 2.783 2.870 3 .943 3-550 5 .200 1.637 3-924 6 . 7 1 1 6 .117 12.30 11.22 3 .692 5.510 12 .72 9 .397 24 -08 18 .00 6 .874 7 .935 21 .80 14.11 33.30 25 .50 11 .96 10 .75 3 4 . 2 6 21 .18 55.78 33.55 17.24 13.21 51 .39 29 .80 22.68 15.40 67.52 38.17 30 .72 17-90 KNO3 0.000 2.616 0.8532 3.147 3.023 5.391 6.052 8.142 10.95 12.35 15.85 16.95 21.04 21.31 27.44 26.00 t e t r a m e t h y l -ammonium c h l o r i d e 0.000 2.652 3.061 4.513 7.357 8.237 11.44 12.57 16.93 19.59 21 .28 26.11 26.28 34.67 30.72 43.06 34.69 50.86 B a C l 2 0.000 2.757 2.661 5.450 6.935 10.86 10.93 15.52 16 .81 22.20 KgCO^ t e t r a p h e n y l - AsF arsonium c h l o r i d e 3 0.000 2.622 0.7154 3-152 1.577 4-499 2.835 6.368 •5 .280 9.915 9.220 16.50 15.00 23.75 20.60 32.78 25.00 • 41 .18 0.000 2.515 0.3773 3.093 1.231 4.744 2.198 6.946 3 .731 11.02 4.963 14.19 6.528 18.29 8.039 22.19 9.344 24.70 not s o l u b l e 57 observed. The most reasonable explanation of these r e s u l t s i s t h a t complete s o l v o l y s i s of the c h l o r i d e occurs to give the metal difluorophosphate and HC1. Over a wide c o n c e n t r a t i o n range the HC1 has no e f f e c t on t h e . c o n d u c t i v i t i e s of the d i f l u o r o p h o s -phates ( i . e . HC1 i s a n o n - e l e c t r o l y t e ) , however, at high con-c e n t r a t i o n s the HC1 could cause a change i n the p r o p e r t i e s of the s o l u t i o n such as v i s c o s i t y , d e n s i t y and d i e l e c t r i c constant which could i n c r e a s e the m o b i l i t i e s of the ions present or i n -crease the degree of d i s s o c i a t i o n of i o n p a i r s and thus produce a higher c o n d u c t i v i t y . I t i s w e l l known tha t i n s o l v e n t s of low d i e l e c t r i c con-s t a n t where i o n a s s o c i a t i o n i s important, s a l t s of l a r g e c a t i o n s show the g r e a t e s t degree of d i s s o c i a t i o n 1 9 . To f u r t h e r t e s t the assumption t h a t metal difluorophosphates are s t r o n g l y a s s o c i a t e d i n HP0 2F 2, c o n d u c t i v i t y s t u d i e s on (CH^)^NCl and (C^H^)^AsCl were made. Since i o n i c c h l o r i d e s apparently undergo complete s o l v o l y s i s (see above) t o the corresponding difluorophosphate and hydrogen c h l o r i d e these complex s a l t s w i l l r e a c t w i t h HP0 2F 2 according to the equation, R^MCl + HP0 2F 2 —* R MP0 2F 2 + HC1 ( 3 . 3 ) ' and i t ' i s thus important to know 'what e f f e c t the HC1 produced w i l l have on the c o n d u c t i v i t y of the s o l u t i o n s . The s t u d i e s on the a l k a l i and a l k a l i n e earth metal c h l o r i d e s have shown that at low concentrations the e f f e c t of the HC1 i s s m a l l and the con-d u c t i v i t y observed i s e s s e n t i a l l y t h a t due to the corresponding difluorophosphate. I t may be assumed th a t the c o n d u c t i v i t y 5 8 curves f o r the R^MCl compounds are e s s e n t i a l l y those of the cor-responding difluorophosphates. While (CH 3)^NP0 2F 2 e x h i b i t s con-d u c t i v i t y values about the same as those of metal d i f l u o r o p h o s -phates the compound (C^H/^^AsPO^Fg i s much more h i g h l y conduct-i n g . I t i s unreasonable t o assume th a t these high c o n d u c t i v i t i e s are due t o a greater m o b i l i t y of the (C^H^)^As + c a t i o n compared to the metal c a t i o n s and must be due t o greater d i s s o c i a t i o n of t h i s s a l t , confirming the former c o n c l u s i o n that the metal d i -fluorophosphates are weakly d i s s o c i a t e d . I n F i g . 13 the c o n d u c t i v i t i e s of potassium n i t r a t e and carbonate are shown r e l a t i v e t o KC1 and KPO^Fg. The c o n d u c t i v i t y produced by KgCO^ s o l u t i o n s i s more than t h a t expected f o r the s o l v o l y s i s of the carbonate t o 2KPO2F2 according t o , KgCO^ + 2 H P 0 2 F 2 ~~* 2 K P 0 2 F 2 + H 2 C 0 3 (3.4) H 2C0 3 —» H20 '+ C0 2 Considerable effervescence was observed during the run presumably due.to the e v o l u t i o n of carbon d i o x i d e . The water t h a t i s thus produced should be protonated t o E^0+ i n t h i s a c i d i c s o l v e n t . Thus the observed c o n d u c t i v i t y f o r the carbonate s o l u t i o n should be g r e a t e r than twice that of a s i m i l a r c o n c e n t r a t i o n KPOgFg s o l u t i o n . However, i t i s not known I f water behaves as a simple base i n the HP0 2F 2 s o l v e n t system; i t i s p o s s i b l e t h a t e q u i l i b r i a of the type, H 20 + HP0 2F 2 5 = * H 2P0 3F + HF H 30 + + P 0 2 F 2 " ^ H 2 P 0 3 F + H F could occur. P r o t o n a t i o n of H 2P0 3F or HF produced i n such reactions-could account f o r the f a c t t h a t the observed c o n d u c t i v i t y i s 6£ 60 g r e a t e r than twice t h a t f o r KPOgFg. 19 Potassium n i t r a t e i s known t o rea c t w i t h s u l p h u r i c and f l u o r o s u l p h u r i c a c i d s to produce the ni t r o n i u m i o n , KN03 + HA ^ HNO^ + A~ + K + (3.5) HNO^ + 2HA ^ N0 2 + + 2A" + H^O* I n d i f l u o r o p h o s p h o r i c a c i d the c o n d u c t i v i t i e s observed f o r KKO3 are much greater than those observed f o r s i m i l a r concentrations of KPO2F2, thus i n d i c a t i n g t h a t some r e a c t i o n i n a d d i t i o n to the simple s o l v o l y s i s r e a c t i o n KNO^ + HP0 2F 2 — • K + + P0 2F 2~ + HNO^ (3.6) i s t a k i n g p l a c e . I t i s not known i f n i t r i c a c i d i s s t a b l e i n HP0 2F 2, nor whether i t would act as an a c i d or base. I t i s d o u b t f u l i f p r o t o n a t i o n of n i t r i c a c i d would occur to any great extent. HNO3 + HP0 2F 2 ^ H 2N0 3 + + P O ^ " (3 .7) During the a d d i t i o n of n i t r a t e brown fumes were observed and the s o l u t i o n was coloured brown, i t thus appears that the n i t r i c a c i d i s unstable and decomposes according t o , 2HNO3 + HP0 2F 2 ^ 2N02 + P 0 2 F 2 " + H 30 + + 0 2 ( 3 . 8 ) The observed c o n d u c t i v i t y values which are greater than those e x h i b i t e d by KP0 2F 2 at the same concentrations could be explained by the presence of t h i s r e a c t i o n . I t i s impossible, at the moment, t o be more q u a n t i t a t i v e , concerning these s t u d i e s as the i o n i c m o b i l i t i e s of the species p o s t u l a t e d and the degrees of d i s s o c i a t i o n of the i o n p a i r s are not known. I t could be, f o r example, th a t the X versus n curve f o r potassium carbonate i s j u s t l e s s than t h a t of 3 x X versus n. curve f o r KP0 2F2 due t o the f a c t t h a t the i o n i c m o b i l i t y of the H^ O i s l e s s than t h a t of K or the degree of d i s s o c i a t i o n of H 30 +P0 2F2- i s l e s s than the degree of d i s s o c i a -t i o n of K + P 0 o F o ~ . 62 CHAPTER IV Acids and Acid-Base Reactions 4.1 I n t r o d u c t i o n Few s u b j e c t s i n chemistry have e x c i t e d more i n t e r e s t and more r e s u l t a n t controversy than the sub j e c t s of a c i d s and bases'^. Acids and bases are regarded as mutual opposites which i n general l o s e t h e i r d e f i n i n g p r o p e r t i e s when brought i n t o , con-t a c t w i t h each other. The solv e n t system concept i s based upon the f o r m u l a t i o n of a c i d i c and basic e n t i t i e s i n a solvent as those species which r e s u l t from the s e l f - i o n i z a t i o n of the s o l v e n t , e.g. 2H 20 ^ H^ O4" + 0H-I n d i f l u o r o p h o s p h o r i c a c i d any s o l u t e which causes an increase i n the d i f luorophosphoric acidium i o n , H^jPO^F^, i o n concentra-t i o n w i l l be considered an a c i d , and correspondingly any s o l u t e which causes an in c r e a s e i n the difluorophosphate i o n , P 0 2 F 2 ~ , c o n c e n t r a t i o n i s a base. 22 I t has been shown that i n the s u l p h u r i c a c i d solvent system HP0 2F 2 i s a base, HSO^F an a c i d and CF^COOH a non-e l e c t r o l y t e and i t i s l i k e l y , t h e r e f o r e , that i n the d i f l u o r o p h o s -p h o r i c a c i d system, the pr o t o n i c a c i d s HSO3F, H2SO4 and CF3COOH w i l l a ct as ac i d s according to (1.5). The expected r e l a t i v e order of a c i d i t i e s i n HP0 2F 2 i s HSO^F > H 2 S O ^ CF^COOH. Lewis a c i d s of the type SbF^, BF^ and AsFc; may a l s o prove t o be acids by being anion acceptors according t o equation ( 1 . 6 ) . I t should be p o s s i b l e t o c a r r y out acid-base n e u t r a l i z a t i o n r e a c t i o n s i n HPO2F2 as i n any other amphoteric s o l v e n t . The n e u t r a l i z a -t i o n r e a c t i o n i s simply the reverse of the s o l v e n t a u t o p r o t o l y -s i s i . e . , H 2 P 0 2 F 2 + + P 0 2 F 2 " — 2 H P 0 2 F 2 (4 . 1 ) -f _ I n s u l p h u r i c a c i d the. a u t o p r o t o l y s i s ions H-^ SO^  and HSO^ have very much higher m o b i l i t i e s than any other ions and thus n e u t r a l i z a t i o n r e a c t i o n s are conveniently f o l l o w e d by e l e c t r i c a l conduc t i m e t r i c methods 4 . As there seems t o be some u n c e r t a i n t y as to whether the a u t o p r o t o l y s i s ions of HPO2F2 e x h i b i t abnormal m o b i l i t y , i t i s a n t i c i p a t e d that there x v i l l be considerable d i f f i c u l t y i n the d e t a i l e d i n t e r p r e t a t i o n of c o n d u c t i v i t y t i t r a -t i o n curves. F u r t h e r , any i o n - p a i r i n g w i l l cause even more d i f -f i c u l t i e s i n the d e t a i l e d i n t e r p r e t a t i o n of the data. 4.2 Experimental ' • A) P r e p a r a t i o n and p u r i f i c a t i o n of m a t e r i a l s . F l u o r o s u l p h u r i c a c i d : commercial HSO3F obtained from A l l i e d Chemical Co. w a s . d o u b l e - d i s t i l l e d at I64 0 and atmospheric 10 pressure. T r i f l u o r o a c e t i c a c i d : Commercial CF^COOH from Eastman Kodak Co. was d o u b l e - d i s t i l l e d at 7 2 ° and atmospheric pressure. .• Antimony pentaf l u o r i d e : commercial SbF^ obtained from A l f a I n o r g a n i c s Inc. was d o u b l e - d i s t i l l e d under vacuo. Sulp h u r i c a c i d : 100$ HgSO^ was made from 98$ "AnalaR" s u l p h u r i c a c i d and d i l u t e oleum according t o the method of minimum conducting a c i d due t o G i l l e s p i e et a l . * - 4 - ' 6Z(. B) E l e c t r i c a l c o n d u c t i v i t y . The c e l l used i s that shown i n F i g . 2 and the procedure adopted f o r the c o n d u c t i v i t y runs has been discussed p r e v i o u s l y . As the s o l u t e s are l i q u i d s , the microburette was used to make the a d d i t i o n s / However, i n the case of antimony p e n t a f l u o r i d e a concentrated s o l u t i o n of SbF^/HPO^Fg was made and t h i s was added by means of the microburette. The s o l u t i o n was made by d i s t i l l i n g SbF^ under vacuo i n t o a clean, dry tube which was then reweighed and t r a n s f e r r e d to the dry box. A s u i t a b l e amount of f r e s h l y d i s t i l l e d HPO2F2 was added to the tube which was then reweighed. The r e s u l t i n g s o l u t i o n u s u a l l y had a concent r a t i o n of 3-5 molal. The tube was shaken v i g o r o u s l y f o r s e v e r a l minutes and l e f t f o r 30-40 minutes to ensure the s o l u t i o n was homo-geneous. The mixing of the two. l i o u i d s 'was exothermic. During the shaking of s o l u t i o n A i n Table 9 the tube was cooled i n l i q u i d n i t r o g e n . A sample of the r e s u l t i n g s o l u t i o n was drown i n t o the microburette and used f o r the c o n d u c t i v i t y run. In a l l cases a f t e r a d d i t i o n of a c i d was complete, base was added by means of the i n j e c t o r ( F i g . 3) pnd the c o n d u c t i v i -t i e s of the r e s u l t i n g s o l u t i o n s recorded. I n the cases of HgSO^, HSO^F and SbF^ white p r e c i p i t a t e s were obtained on the a d d i t i o n of base. The l i c u i d was removed by f i l t r a t i o n and the p r e c i p i -t a t e washed w i t h H P 0 2 F 2 , d r i e d by pumping o f f the excess acid at room temperature and stored over phosphoric oxide i n a d e s i c -c a t o r . C) Nuclear magnetic resonance. The 1H, 1 9 F and 3 1 P spectra of s o l u t i o n s of SbFc, i n HPOgFg were obtained on a Va r i a n HA100 h i g h - r e s o l u t i o n spectro-meter operating under the co n d i t i o n s described p r e v i o u s l y . C a l i b r a t i o n of the s p e c t r a was obtained by l o c k i n g on t o a s u i t -able peak e.g. i n the phosphorus spectrum the c e n t r a l peak of the t r i p l e t was used, and scanning over 1000 c y c l e sweep widths. The s o l u t i o n s s t u d i e d were of a higher c o n c e n t r a t i o n ( u s u a l l y 2.5 molal) than those s t u d i e d c o n d u c t i m e t r i c a l l y and were ex-amined at room temperature and at around -70°. 4.3 P r o t o n i c a c i d s : R e s u l t s and d i s c u s s i o n I n Table 9 "the r e s u l t s of the c o n d u c t i v i t y measure-ments on s o l u t i o n s of the pro t o n i c a c i d s i n HPOgFg at 25° are given. I n F i g . 14 the s p e c i f i c conductances are p l o t t e d a g a i n s t the molal c o n c e n t r a t i o n , m. The c o n d u c t i v i t y curves of H S O 3 F and H^SO^ show an i n i t i a l f l a t p o r t i o n f o l l o w e d by a l i n e a r i n c r e a s e i n c o n d u c t i v i t y w i t h concentration. The f l a t p o r t i o n of the curves could be a t t r i b u t e d t o t i t r a t i o n of b a s i c i m p u r i t y i n the d i f l u o r o p h o s p h o r i c a c i d . However, i t i s p o s s i b l e t h a t i n d i l u t e s o l u t i o n s the a c i d s are q u i t e weak but at higher concentrations where s o l u t e - s o l u t e i n t e r a c t i o n i s p o s s i b l e the polymerized forms of the acid s are much stronger and are capable of greater proton donation to sol v e n t molecules. At the same concent r a t i o n the c o n d u c t i v i t i e s increase i n the order CF^COOH< HgSO^< HSO3F. D e f i n i n g a c i d strengths i n terms of the concen t r a t i o n of the f r e e ions H oP0 oF o H and A" 1 0 2 m TABLE 9 S p e c i f i c Conductances of Some Acids at 25 H 2 S 0 4 CF3COOH ohm -Lcm. 102m 0.000 2.710 0.1514 2.729 0.5552 2.772 1.393 2.860 2.645 2.999 4.502 3.201 7.107 3.486 9.994 3.810 15.01 4.368 20.02 4.915 24.02 5.347 28.08 5.773 32.11 6.191 36.15 6.600 40.19 7.001 A d d i t i o n of K P 0 2 F 2 T o t a l 0.9944 41.18 7.355 3.294 43.48 8.353 5.990 46.18 9.713 1 0 ^ ohm-^cmr-1-0.000 0.2902 0.5223 0.8560 1.407 2.162 2.916 3.671 4.837 6.239 8.183 10.65 13.09 16.31 19.28 23.65 28.29 34.18 40.10 49.33 59.11 A d d i t i o n Tota 0.8763 59 2.939 62 7.455 66 IO .46 69 2.837 2.805 2.B19 2.795 . 2.770 2.773 2.811 2.369 2.982 3.156 3.444 3.851 4.280 4.874 5.433 6.336 7.337 8.679 10.07 12.45 15.13 of KPOoF 1 .99 15.05 .10 14.40 .57 11.35 .57 10.05 2*2 102m HSO3F 10^K ohm-lcmrl 0.000 2.485 0.2830 2.525 O.566O 2.540 O.848O 2.578 1.4-15 2.698 1.697 2.732 2.420 2.885 2.850 2.960 0.000 2.553 0.1450 2.556 0.5517 2.537 1.277 2.682 2.338 2.879 3.938 3.222 6.166 3.785 8.676 4.466 12.32 5.591 0.000 2.580 11.80 5.020 17.70 7.460 23.60 9.790 29.50 12.19 42.00 18.86 53.10 24.60 A d d i t i o n of NH 2P0 2F 2 T o t a l V 6.79 59.39 19.33 22.9 76.00 10.25 45.6 98.70 4.48 61.3 114.90 8.16 TABLE 9 (cont'd) A B SbF^ SbF 5 I n i t i a l conc'n of I n i t i a l conc'n of SbF 5/HP0 2F 2 = 3.733m. SbF^/HPO^ = 5.484m. 102m 10/lX 102m 10*11 ohm~lcmrl ohm~lcmr-0.000 2.732 0.000 2.574 2.097 3.079 0.1654 2.595 5.378 4.476 0.3221 2.626 10.18 7.080 0.5361 2.674 16.10 10.96 O.8488 2.741 Added KPOoFo 1.201 2.832 T o t a l 1.615 3.027 11.22 27.32 6.035 2.076 3.186 21.68 37.78 6.040 2.635 3.415 23.72 39.82 7.286 3.342 3.675 4.201 4.051 5.338 4.686 7.356 5.461 9.122 6.272 I I . 6 4 7.531 14.13 8.781 17.49 10.53 21.43 12.69 25.39 14.96 29.48 17.36 33.43 19.27 Added KP0?F 9 T o t a l 3.042 36.47 17.69 8.247 41.68 14.95 19.21 52.64 9.427 30.25 63.68 7.756 32.69 66.12 8.257 38.64 72.07 9.900 46.38 79.81 12.95 69 i n s o l u t i o n , the higher c o n d u c t i v i t i e s e x h i b i t e d by HSO3F s o l u -t i o n s suggest t h i s a c i d i s the strongest a c i d of the three i n d i f l u o r o p h o s p h o r i c a c i d s o l u t i o n . I n s u l p h u r i c a c i d s o l u t i o n s 22 other workers have shown that HPO2F2 i s a weak base of the H2SO4 system and the r e s u l t s reported here shov/, as would be ex-pected, that i n the HPO2F2 system. R^SO^ i s only a weak a c i d causing l i t t l e p r o t o n a t i o n and hence producing few i o n s and a low c o n d u c t i v i t y . A l s o from the s u l p h u r i c a c i d work i t . has been suggested t h a t CF^COOH i s a weaker base than HPO2F2, i n f a c t i t i s a n o n - e l e c t r o l y t e , and hence i t seems l i k e l y t h a t i n the HPO2F2 system CF^COOH'will be a weak acid, of comparable stren g t h t o R^SO^. From the c o n d u c t i v i t y curves i n F i g . 14 i t appears t h a t CF3COOH i s i o n i z e d to a smaller extent than the i n o r g a n i c oxy-acids. The e f f e c t of adding base to s o l u t i o n s of the p r o t o n i c a c i d s was f o l l o w e d c o n d u c t i m e t r i c a l l y and the r e s u l t s are sho\vn i n F i g . 15. For H^SO^ and HSO^F s o l u t i o n s a white s o l i d separ-ated and the c o n d u c t i v i t y decreased. I n the case of HSO^F the base,-NH 4P0 2F 2, was added u n t i l the c o n d u c t i v i t y increased again; the base was added to a 0 .531 molal s o l u t i o n of HS0^F/HP0 2F 2 and a minimum was obtained at a t o t a l m o l a l i t y of 1 .05. I t t h e r e f o r e appears th a t the base n e u t r a l i z e s the HSO^F i n a 1:1 r e a c t i o n , HSO3F + HP0 2F 2 — H 2 P 0 2 F 2 + + S0 3F~ (4.2) NH 4P0 2F 2 ^ P0 2F 2- + N H 4 + The white s o l i d \^as i d e n t i f i e d as MH^SO^F by comparing i t s i n f r a -r e d spectrum-with that reported by D. W. A. S h a r p . 4 5 The observation 71 of the production of the s a l t NH^SO^F, of course, confirms the previous assumption t h a t HSO-jF behaves as an a c i d i n HPO2F2 s o l u t i o n s . A d d i t i o n of the base K P 0 2 F 2 t o the H2S0^/HP02F2 s o l u t i o n caused the p r e c i p i t a t i o n of KHSO^ which was i d e n t i f i e d by i t s m e l t i n g p o i n t (210 )° and i t s i n f r a r e d spectrum (compared to t h a t of an authentic sample of KHSO^ - Baker A. R. Grade). HgSO^ + H P 0 2 F 2 ^ H 2 P 0 2 F 2 + + KSO^" ( 4 . 3 ) K P 0 2 F 2 ^ P 0 2 F 2 ~ + K + Again, the ob s e r v a t i o n of the production of KHSO^ confirms the assumption t h a t H 2 S 0 ^ behaves as an a c i d . i n l I P 0 2 F 2 . A d d i t i o n of the base K P 0 2 F 2 t o the CF^COOH/HPC^Fg s o l u t i o n causes the conduc-t i v i t y t o increase and no p r e c i p i t a t e i s formed. As no product from the r e a c t i o n of CF3COOH w i t h K P 0 2 F 2 i n H P 0 2 F 2 was i d e n t i f i e d i t i s not p o s s i b l e t o say f o r c e r t a i n t h a t t r i f l u o r o a c e t i c a c i d i s behaving as an a c i d i n H P 0 2 F 2 . I t i s p o s s i b l e that CF3COOH is.behaving as an a c i d and the s a l t formed on adding K P 0 2 F 2 , CF 3 C00K i s s o l u b l e i n HP02F2« U n f o r t u n a t e l y no s t u d i e s on the s o l u b i l i t y of t h i s s a l t i n HPO2F2 have been made as yet. The increased c o n d u c t i v i t y observed on a d d i t i o n of KPO2F2 t o the s o l u t i o n s of CF^COOH could be due t o a greater degree of d i s -s o c i a t i o n of.CF^COOK over t h a t of CF3COOH. I t had been hoped that the acid-base t i t r a t i o n s would giv e some i n d i c a t i o n as to whether abnormal conduction i s shown by the a u t o p r o t o l y s i s i o n s of H P 0 2 F 2 . I n H 2 S 0 ^ conductimetric a c i d -base t i t r a t i o n s have confirmed that the H^SO^ i o n has an abnor-43 mally high m o b i l i t y . A d d i t i o n of KHSO, t o a s o l u t i o n of an a c i d (e.g. HB(HSO ) ) causes a marked decrease i n the conduc-t i v i t y as the h i g h l y mobile H^SO^4" i o n i s r e p l a c e d by the r e l a t i v e l y p o o r l y conducting K""" i o n . However, i n HPO2F2 a d d i t i o n of base causes p r e c i p i t a t i o n i n the cases of HSO3F and H 2S0 4 and thus a a l o s s of ions due to the i n s o l u b i l i t y of the s a l t . The decrease i n c o n d u c t i v i t y cannot be a t t r i b u t e d t o the replacement of the H 2 P 0 2 F 2 + i o n by the M + i o n . 4 . 4 S o l u t i o n s of antimony p e n t a f l u o r i d e : R e s u l t s and d i s c u s s i o n . From a study of the chemical r e a c t i o n s of a l a r g e number of f l u o r i d e s i n s o l u t i o n i n hydrogen f l u o r i d e , C l i f f o r d et a l . 4 ^ concluded t h a t some, s o l u t e s e x h i b i t e d a c i d behaviour by a c t i n g as f l u o r i d e i o n acceptors. The pentafluorid.es of Sb, As and P were found t o be a c i d s which decreased i n str e n g t h i n the order SbF^> A s F ^ > P F y The f i r s t q u a n t i t a t i v e study of s o l u t i o n s of SbF 5 i n HF was made by K i l p a t r i c k and Lewis*" 7 who stu d i e d the e l e c t r i c a l c o n d u c t i v i t i e s of s o l u t i o n s of SbF^ and a l s o of KF, 48 NaF and NaSbF^. Hyman et a l . i n v e s t i g a t e d the i n f r a r e d and Raman spectr a of SbF5 s o l u t i o n s i n hydrogen f l u o r i d e and obtained evidence f o r the formation of the SbF^" i o n . Their work a l s o i n -cluded a.study of the e l e c t r i c a l c o n d u c t i v i t i e s of the HF-SbF^ system over the whole range of composition, but not of very 49 d i l u t e r e g i o n s . Hyman and Katz concluded that i n HF the net r e s u l t .of the a d d i t i o n of a ILuoride i o n acceptor i s p r e c i s e l y the same as the a d d i t i o n of a proton donor, namely an increase i n the co n c e n t r a t i o n of s o l v a t e d protons, SbF.5 + 2HF = H 2 F + + SbFg" . (4 .4) G i l l e s p i e and Moss'^ were able to confirm the conduc-t i v i t y r e s u l t s of Hyman et a l . at high c o n c e n t r a t i o n s , however, at low SbF^ concentrations the c o n d u c t i v i t i e s obtained were much higher than those of K i l p a t r i c k and Lewis. They a l s o s t u d i e d the 1 9 F and -4-1 n«.m.r. spectr a of a number of SbF^/HF s o l u t i o n s . I n the case of the proton n.m.r. the s o l u t i o n s gave only one s i g n a l even at low temperatures, whereas the f l u o r i n e spectrum contained s e v e r a l peaks which were assigned t o a dimeric i o n S"b2 Fll"> SbF^ - and HF. The Sb2F]_]_~ i o n was b e l i e v e d to form at h i g h SbF^ concentrations due t o the r e a c t i o n , S b F 6 ~ + S b F r S b 2 F 1 : L - ' (4 .5) I n view of the f a c t t h a t SbF.^ i s i t s e l f h i g h l y polymerized, i t was a l s o suggested t h a t higher polymeric i o n s , such as Sb^F-^g" and Sb^_F2-]_~, may be present i n the more concentrated s o l u t i o n s . 51 52 Woolf and B a r r both i n v e s t i g a t e d s o l u t i o n s of a n t i -mony p e n t a f l u o r i d e i n f l u o r o s u l p h u r i c a c i d and Woolf suggested two p o s s i b l e modes of i o n i z a t i o n f o r t h i s s o l u t e , namely S b F r + 2HS0oF =^ S b F r S C k F " + H9SO,,F+ .. 1 5 3 ( 4 . 6 ) S b F r •+ 2HS0 3F S b F 6 ~ + SO^ + H 2 S 0 3 F + 2 Woolf suggested t h a t equation 2 i s more probable than 1 because the s t r u c t u r e SbF^SO^F" would r e q u i r e abnormal f i v e - f o l d co-o r d i n a t i o n of sulphur while the a l t e r n a t i v e s t r u c t u r e SbF^SO^" would r e q u i r e seven-fold c o o r d i n a t i o n of antimony. Barr, however, pointed out t h a t i f the f l u o r o s u l p h a t e group i s bonded to an-timony v i a oxygen, no abnormal c o o r d i n a t i o n i s r e q u i r e d . 5 3 F u r t h e r work by Thompson et a l . i n v o l v e d c o n d u c t i m e t r i c , cryoscopic and nuclear magnetic resonance s t u d i e s on s o l u t i o n s of. S0F5, S D F 4 S O 3 F and S D F 5 - SO3 mixtures i n f l u o r o s u l p h u r i c a c i d . They were able t o shov/ th a t a s e r i e s of a c i d s e x i s t w i t h the general formula H ( s b F 5 _ n ( S 0 3 F ) 1 + n ) where n^O, 1, 2 and 3.. Dimeric and probably higher polymeric forms of these a c i d s were suggested t o be present i n the s o l u t i o n s a l s o and n.m.r. st u d i e s showed th a t p o l y m e r i z a t i o n occurs through f l u o r o s u l p h a t e bridges. From the r e s u l t s of the SbF^/HF and SbF^/HSO^F systems i t was expected t h a t i n the HP0 2F 2 solvent system SbF^ would prove t o be a strong a c i d and a difluorophosphate anion acceptor ac-cording t o , . SbF 5 + 2HP0 2F 2 ^ SbF 5P0 2F 2"'+ H 2 P 0 2 F 2 + (4 .7) As the c o n c e n t r a t i o n of the SbF^ i n c r e a s e s , i t i s p o s s i b l e that more h i g h l y polymeric species may be formed as found i n the HF and HSO^F solvent systems. I n Table 9 the r e s u l t s of the c o n d u c t i v i t y measurements of s o l u t i o n s of SbF^ i n HP0 2F 2at 25° are given and p l o t t e d a g a i n s t m o l a l i t y , m, i n F i g . 14. The SbF^ s o l u t i o n s are more conducting at the same concentrations than HSO^F and H 2S0 4 s o l u t i o n s which i s i n agreement vriLth the r e l a t i v e order f o r the a c i d s t r e n g t h s , SbF^> HSO^F^gSO^. A d d i t i o n of K P 0 2 F 2 causes the c o n d u c t i v i t y t o decrease and a white s o l i d t o separate. I n F i g . 16 two sets of data are shown and i n the more d i l u t e SbF^ s o l u t i o n (curve A) the a d d i t i o n of base produces a minimum i n the c o n d u c t i v i t y at approximately the end point f o r a 1:1 r e a c t i o n of SbF c and K P 0 o F o . 76 SbFr + HP0 2F 2 - HSbF.P02F|'-!- HP0 2F 2 ^ H 2P0 2F 2 + + SbFrP0 2F 2~ (4.8) •KP0.2F2 ^ • P0 2F 2- +./ K + I t i s d i f f i c u l t to be c e r t a i n e x a c t l y where the minimum i n the c o n d u c t i v i t y t i t r a t i o n curve occurs; however, i t appears t h a t , from the t i t r a t i o n of the more concentrated s o l u t i o n of SbF r 5 (curve B ) , the minimum occurs at a mole r a t i o of base to a c i d of s l i g h t l y l e s s than one. A l s o , the c o n d u c t i v i t y at the minimum i s grea t e r than t h a t of the pure s o l v e n t . These observations lead one t o suspect t h a t r e a c t i o n s - i n a d d i t i o n to (4-3) are t a k i n g p lace and t h i s c o n c l u s i o n i s confirmed by the n.m.r. st u d i e s t o be presented l a t e r . The n.m.r. sp e c t r a of v a r i o u s SbFr_/HP02F2 s o l u t i o n s were taken at -70° and 30° f o r 1 9 F , 3 1 P and hi and these are l i s t e d below: spe c t r a m o l a l i t y temperature : : 3.63 30°, -65° 19 F ' 3.63 30°, -65° shown i n F i g s . 17 & 18 !9F 2.31 30°, -65° d e t a i l s shown i n Figs.2 0 , 2 1 , 2 2 & 23 31 P 2.31 30°, -70° d e t a i l s i n Fig.25 3'lp 2.62 30° .shown i n F i g . 24 31 P 2.27 30°, -70° I n the n.m.r. spectrum only one proton s i gnal i s observed at 30° and -70° thus i n d i c a t i n g t h a t ': r a p i d proton t r a n s f e r must be o c c u r r i n g between the v a r i o u s species present i n s o l u t i o n . ^ Molecules such as H(SbF 5P0 2F 2) and i t s anion S bF 5P0 2F 2" w i l l be i n e q u i l i b r i u m according t o , --alternate form i s SbF^HPOgFg). 77 HSbFrP0 2F 2 + HP0 2F 2 ^ SbF 5P0 2F 2~ + H 2 P 0 2 F 2 ( 4 . 9 ) because of the r a p i d proton t r a n s f e r only a s i n g l e -^P and 1 9 F n.m.r. spectrum w i l l be observed f o r these two antimony species. For s i m p l i c i t y i n the remainder of t h i s d i s c u s s i o n , the spectra w i l l be assigned t o n e u t r a l e n t i t i e s only, i t being understood t h a t the spectr a are probably combined spectra of the anions and t h e i r corresponding n e u t r a l protonated molecules. Considering f i r s t the n.m.r. s p e c t r a , the general f e a t u r e s of the two s o l u t i o n s s t u d i e d (3.63 and 2.31 molal SbF,-) were the same; both s p e c t r a were obtained on 1000 c/s se c t i o n s and i n the case of the more concentrated s o l u t i o n a l s o on a s i n g l e scan which i s shown i n F i g . 17. Only the s p e c t r a of the 2.31 m o l a l s o l u t i o n w i l l be discussed i n d e t a i l as i n the spectrum of the 3«63 molal s o l u t i o n s e v e r a l peaks went o f f s c a l e . At room temperature'in the r e g i o n of the spectrum due t o f l u o r i n e bonded to phosphorus s e v e r a l sharp peaks were observed w h i l e i n the r e g i o n due to f l u o r i n e bonded to antimony a few very broad resonances were present. These l a t t e r resonances are presumably broadened by f l u o r i n e exchange at room temperature. At -65° some broadening ( c f . F i g . 20) was observed i n the peaks due t o f l u o r i n e bonded t o phosphorus (probably due to inc r e a s e d v i s -c o s i t y of the s o l u t i o n s ) w h i l e f i n e s t r u c t u r e i n the r e g i o n of f l u o r i n e bonded t o antimony was observed. I n F i g s . 17 and 18 the e n t i r e 1 9 F s p e c t r a at 30° and -65° r e s p e c t i v e l y are shown. The l a r g e doublet ( l a b e l l e d D and I i n F i g . 17) i s assigned t o solve n t and on d i l u t i o n w i t h HP0 2F 2 to produce a SbF^/HP0 2F 2 s o l u t i o n of about 1 molal c o n c e n t r a t i o n the peaks D and I F i g . 17 1 9 F N.M.R. Spectrum of a 3-63 molal SbF_/HP0_Fo S o l u t i o n at 30° 5' 2 2 D F i g . 19 F N.M.R. Spectrum of a 7.0 molal S b F 5 / H P 0 2 F 2 S o l u t i o n at 30° CO-o ( i n s e t F i g . 17) c l e a r l y shov/ a l a r g e increase thus confirming t h e i r assignment to s o l v e n t . I n F i g s . 20-22 d e t a i l s of the .two r e g i o n s f o r the 2.31 molal s o l u t i o n are given. The 3.000 c/s s i d e bands produced by the spectrometer u n f o r t u n a t e l y confuse the o v e r a l l s p e c t r a ; however, u s i n g 1000 c/s sweep widths and the "lock-on" technique e l i m i n a t e s these side bands. Unfort u n a t e l y i t i s not p o s s i b l e to c o r r e l a t e areas under the peaks or peak hei g h t s i n F i g s . 17 and 18 w i t h the number of f l u o r i n e atoms i n the proposed species assigned t o a peak, as i n the scan of the complete spectrum overlap of modulation side bands a l t e r s the peak heights and areas. On the scan of the 1000 c/s sweep widths spectrometer c o n d i t i o n s were changed from one spectrum to another so t h a t a peak could be magnified by s e v e r a l times and hence i t s height or area would not give a t r u e r e p r e s e n t a t i o n of the number of f l u o r i n e s . A f i n a l d i f f i c u l t } / - l a y i n the f a c t t h a t the s o l u -t i o n s were so d i l u t e that i n order to record any- small peaks the m a g n i f i c a t i o n had t o be so l a r g e t h a t the peaks due to s o l v e n t went o f f s c a l e and could not be measured. I n Table 10 a l l the peaks observed, t h e i r m u l t i p l i c i t y and c o u p l i n g constants (J) are given; the chemical s h i f t s are measured i n c y c l e s per second from the centre of the doublet due t o the s o l v e n t and are the average values f o r a l l the 1 9 F s p e c t r a examined. At high f i e l d s t r e n g t h s , i n the r e g i o n of the spectrum due t o f l u o r i n e bonded to antimony, the spectrum i s composed e s s e n t i a l l y of a d o u b l e t - q u i n t e t p a t t e r n ( l a b e l l e d M and P i n F i g s . 18, 21 & 22a) and a t r i p l e t - t r i p l e t p a t t e r n ( l a b e l l e d TABLE 10 "^°T and ^ l p Chemical S h i f t s * and Coupling Constants f o r Some Complex Antimony-Fluorine Species Species S b F 5 P 0 2 F 2 SbF rS0 oF 5 3 5 3 1 9 F Chemical S h i f t s * (I) Doublet(CH) -50 l i b Doublet(BG) -87 53 ( S b F 4 ( S 0 3 F ) ) 2 ^ H a l i b Unknown POF3 Doublet(EJ) 469 J Doublet(M) 9 3 3 ^ 2708 (SbFjp ( P 0 2 F 2 ) ) • I l a Doublet(AF) J x -98 994 J 990 J 1060 Doublet 8450 T r i p l e t ( K ) • 1735 T r i p l e t ( F ) 7832 Quintet(P) 4254 Quintet 10123 T r i p l e t ( N ) 3190 T r i p l e t ( P ) 9275 AS 1546 AS 1678 J 114 J 126 1994 S i n g l e t ( H ) 8129 Singlet ( 0 ) 3510 ,J 103 J 100 S i n g l e t ( L ) AS K N A& 1445 KL 259 ASFP A$FH 1443 297 * Measured from the centre of the doublet due t o solvent CO-TABLE 10 (cont'd) • 1 9F and -^P Chemical S h i f t s * and Coupling Constants f o r Some Complex Antimony-Fluorine Species Species 31p Chemical S h i f t s * SbF,P0 oF o . T r i p l e t ( C H L ) J ? * * • 273 986 (SbF.(P0 oR)) l l a T r i p l e t (DI,M) J 4 * A. x 3 2 0 . 1 988 l i b T r i p l e t ( E I 9 N ) J 327 989 •POF, Quartet(AGKO) J ^ 583 1059 * Measured from c e n t r a l , peak of solvent t r i p l e t co. 8 4 19 Fig. 2 0 F N.M.R. Spectra of the P-F Region for a 2.31 molal S b F 5 / H P 0 2 F 2 Peak E (Fig. IS) i s used as ' a 'lock" 30° J • - 7 0 ' A B 4 6 0 4 7 1 516 5 4 8 • 514 - 5 0 0 - 4 6 5 - 4 1 0 H c/s-* F i g . 22(b) i 9 F N.M.R. Spectrum i n the Sb-F .Region f o r a 2.31 molal SbF^/HPO^ S o l u t i o n at -70 ° (peaks N & 0 ) i Peak E ( F i g . 18) i s used as a " l o c k " K and N i n F i g s . 18, 22a & 22b) and two s i n g l e peaks ( l a b e l l e d . L & 0 i n F i g . 18). The doublet - q u i n t e t p a t t e r n i n d i c a t e s t h a t the expected r e a c t i o n , S b F r + HP0 2F 2 -> HSbFrP0 2F 2 (4.7) does indeed take p l a c e . A s s i g n i n g s t r u c t u r e I t o the species HSbF rP0„F„ I the peaks (M) are due to the four equivalent f l u o r i n e atoms, F]_, s p l i t i n t o a doublet by spin-spin- c o u p l i n g w i t h F 2. The q u i n t e t (P) i s due t o F 2 s p l i t ' b y the four equivalent f l u o r i n e s , F-^ . The doublet and qu i n t e t are shown i n more d e t a i l i n F i g s . 21 and 22 r e s p e c t i v e l y . The observed coupling constants and chemical s h i f t s compare remarkably w e l l w i t h those observed f o r the species HSbF^SO^F^. The peaks (C & H) i n the f l u o r i n e on phosphorus r e g i o n ( F i g s . IS & 20) are t e n t a t i v e l y assigned to the f l u o r i n e atoms F^. The remainder of the peaks observed i n the ^ 9 F spectrum must be due t o species produced i n r e a c t i o n s other than ( 4 . 7 ) . The peaks l a b e l l e d E and J ( F i g . 18) are assigned t o POF^. This assignment i s based on the observed coupling constant of 1060c/s ( c . f . l i t e r a t u r e value of 1055c/s)"^+ and the f a c t that a quartet e x h i b i t i n g the same coupling constant appears i n the -^P spectrum 89 ( s e e l a t e r ) . The two t r i p l e t s (K and N) and one s i n g l e t , L, a r e a s s i g n e d t o p o l y m e r i c (SbF^POgFg).^. C i s P 0 2 F 2 b r i d g i n g i n t h i s m o l e c u l e ( s t r u c t u r e l l a ) F 6 F6 F6 F 6 •\ / \ / \ F4 F4 ^ p \ . F 4 ^ ° \ 1 0. I ° \ I 0 S b C T _^ J ^ S b ^ f F 5 I ^ F 5 F 5 | ^ F 5 F 5 | ^ F 5 F4 F4 F 4 l l a w o u l d g i v e r i s e t o t h e A 2 X 2 s p e c t r u m o b s e r v e d i n t h e f l u o r i n e on 55 a n t i m o n y r e g i o n / ' ' w h i l e t r a n s P 0 2 F 2 b r i d g i n g ( l i b ) w i l l g i v e r i s e t o t h e s i n g l e t , L. Fg. ^ - F g F7 ^ P C ^ F 7 F 7 ^ I ^ 0 0 I ' F 7 ^ T S b J^sh^T ^ 0 ^ ^ 0 I F 7 F7* I 0. ^ - 0 ^ : P C T f7 1 f7 J: Fg ^ F g F ^ ^ F g l i b The two t r i p l e t s , K and W, (N i s shown i n more d e t a i l i n F i g . 22) a r e a s s i g n e d t o t h e f l u o r i n e s F 4 a n d Fr, and t h e s i n g l e t , L, t o F y . P e a k s A & F and B & G i n t h e f l u o r i n e on p h o s p h o r u s r e g i o n a r e t e n t a t i v e l y a s s i g n e d t o F Q and Fg, r e s p e c t i v e l y . The a s s i g n m e n t o f - t h e s e p e a k s i s b a s e d l a r g e l y on a n a l o g y o f t h e o b s e r v e d s p e c -t r u m w i t h t h e compound ( S b F ^ S O ^ F ^ w h i c h h a s b o t h c i s and t r a n s , b r i d g i n g f l u o r o s u l p h a t e g r o u p s . The c h e m i c a l s h i f t s and c o u p l i n g c o n s t a n t s ' ^ o b s e r v e d f o r (SbF^SO^F)^ and ( S b F ^ P C ^ F ^ ^ a r e compared i n T a b l e 10. 9 0 A p o s s i b l e e x p l a n a t i o n f o r the formation of POF^ and ( S b F ^ P 0 2 F 2 ) x i n these SbF^/HP0 2F 2 s o l u t i o n s i s th a t at hig h concentrations of SbFtj the f o l l o w i n g r e a c t i o n takes p l a c e , 2SbF 5.HP0 2F 2 SF* ( s b F 4 P 0 2 F 2 ) 2 + 2HF (4.10) S i m i l a r r e a c t i o n s can be w r i t t e n f o r the formation of polymers l a r g e r than the dimer. The HF may then undergo r e a c t i o n w i t h HP0 2F 2 t o produce POF^, HF + HP0 2F 2 ^ POF3 + H 20 (4.H) The s i n g l e peak, 0, i n the f l u o r i n e on antimony r e g i o n may be due to HF or p o s s i b l y HSbF^ produced by the r e a c t i o n , HF + SbF 5 - v HSbF/5 (4 .12) I n F i g . 1 9 the 1 ° T n.m.r. spectrum at room temperature of a more concentrated s o l u t i o n of SbF^ i n HP0 2F 2 (7 molal) i s shown. I t I s apparent t h a t the spectrum i s qu i t e complex w i t h many d i f - . f e r e n t types of f l u o r i n e bonded t o phosphorus I n the P-F r e g i o n of the spectrum. At high SbF^ concentrations i n HP0 2F 2 i t i s expected t h a t p o l y m e r i z a t i o n of SbFrj, which occurs i n the pure 56 l i q u i d , w i l l a l s o occur i n HP0 2F 2 and thus species of a complex nature w i l l form. I t i s p o s s i b l e t h a t species of the type ( S b F 3 ( P 0 2 F 2 ) 2 ) x may a l s o be produced and would thus complicate the n.m.r. spectrum. I t i s not known i f these polymeric forms w i l l be f u r t h e r s o l v o l y z e d t o species of the type H S b F ^ ( P 0 2 F 2 ) 2 and H S b F 3 ( P 0 2 F 2 ) 3 . These r e a c t i o n s could account f o r the seemingly l a r g e amount of POF^ I n the 1 9 F spectrum i n F i g . 1 9 . At the moment an endeavour t o i n t e r p r e t s p e c t r a of t h i s type w i l l not be attempted u n t i l the i s o l a t i o n and d e f i n i t e i d e n t i f i c a t i o n of some of these SbF^/PO^F^ species has been accomplished. I t should be mentioned th a t the c o n d u c t i v i t y r e s u l t s (curve B i n F i g . 16) of SbF^/KPO^Fg t i t r a t i o n s support the ideas suggested p r e v i o u s l y , as the end point f o r the K P O 2 F 2 t i t r a t i o n i n the more concentrated SbF^ s o l u t i o n i s l e s s than t h a t expected f o r a 1:1 r e a c t i o n i t thus appears th a t not a l l the SbF5 i s i n the form of HSbF 5P0 2F 2. F i n a l l y , s p e c t r a were a l s o run under h i g h - r e s o l u t i o n on 100 c/s sweep widths and i n F i g . 23 the ~ 9 F n.m.r. spectrum of peaks F, G and H observed i n the r e g i o n due t o f l u o r i n e bonded to phosphorus are shown. P r e v i o u s l y , the peaks C and H were assigned t o the f l u o r i n e atoms, Fg, I n s t r u c t u r e I and i f these two e q u i -v a l e n t f l u o r i n e s were to couple w i t h the four equivalent f l u o r i n e s , F J L , on the antimony atom then under high r e s o l u t i o n a q u i n t e t p a t t e r n should be observed. As can be seen from F i g . 23 peak H appears as a q u i n t e t w i t h a c o u p l i n g constant, J , of 1.5c/s. Peaks B and G were assigned to Fg i n s t r u c t u r e l i b and under high r e s o l u t i o n the c o u p l i n g of Fg w i t h the f l u o r i n e s on antimony (Fy) should give a nonet. Peak G i s r e s o l v e d i n t o a t r i p l e t which i s , probably the c e n t r a l l i n e s of g r e a t e s t i n t e n s i t y i n the nonet; the remaining peaks w i l l not be observed on the s c a l e used. Peaks A and F were assigned t o F^ i n s t r u c t u r e I l a , which w i l l couple w i t h the two s e t s of equivalent f l u o r i n e s on antimony (F^ and Fc_) . and produce two q u i n t e t s . I n F i g . 23 i t can be seen th a t these two q u i n t e t s overlap and are not r e s o l v e d . The -^P•spectrum ( F i g . 24) v e r i f i e s the previous a s s i g n -ments and i n Table 10 a l l the peaks observed, t h e i r m u l t i p l i c i t y F i g . 23  yY High^Resolution N.M.R. Spectrum of the P-F Region f o r 2 . 3 1 molal SbF / H P 0 2 F 2 S o l u t i o n at 30° Peak DC ( F i g . 18) i s used as a."lock" H 891.1 9 0 2 . 2 948 B F F i g . 24 3 l p N.M.R. Spectrum of a 2.62 molal SbF t./HP0 2F 2 S o l u t i o n at 30° y v y v l hy-2 K M, W A u vO V o F i g . 25 D e t a i l s of the 3 1 p N.M.R. Spectrum of a 2.62 molal SbF^/HPO^ • S o l u t i o n at 30° Peak F ( F i g . 24) i s used as a " l o c k " K L 1095 1249 1301 1315 Hc/s 0 and c o u p l i n g constants, J , are recorded, measurements are from the centre peak of the t r i p l e t and are the average values of a l l the s p e c t r a . As the -^ -p n.m.r. spectrum obtained at +30° and -70° •showed the same general f e a t u r e s only the spectrum observed at +30° i s given (Fig.2 4 ) and d e t a i l s of a part of the spectrum aie shown i n F i g . 25. 54 The t r i p l e t BFJ i s assigned to the solvent and the quar-t e t AGKO i s assigned t o POF^ (J=1059c/s). Three a d d i t i o n a l t r i p - ' l e t s are observed CHL, B I - L M and E I 2 N ( d e t a i l s of K, L, M & N are shown i n F i g . 25) which may be assigned t o P atoms bonded to F^, and Fg f l u o r i n e atoms i n s t r u c t u r e s I , I l a and l i b respec-t i v e l y . Under high r e s o l u t i o n no f i n e s t r u c t u r e was observed as , the peaks were broad and the background noise was of a high l e v e l . 4.5 Studies on KSbF cP0 oF o The white s o l i d which p r e c i p i t a t e d from s o l u t i o n on the a d d i t i o n of the base, KPO^F^, to a 0.16m s o l u t i o n of SbF^ i n HPOgFg was washed w i t h HPC^Fg, d r i e d by pumping o f f the a c i d and s t o r e d over phosphoric oxide. No attempt was made to r e c r y s t a l -l i z e the s o l i d and i t was hoped t h a t by washing the s o l i d w i t h HPC^Fg the product would be e s s e n t i a l l y pure. The a n a l y t i c a l data obtained from A. Bernhardt ate given below: obtained c a l c u l a t e d f o r KSbFrP0 2F 2 %F 36.98 37.25 %?• 8.51 8.69 From the f l u o r i n e and phosphorus analyses i t appears that the formulation,'KSbF^POgF 2 i s a reasonable one and together w i t h the c o n d u c t i v i t y and n.m.r. r e s u l t s i t would seem t h a t the species 96 SbF^P02F2 does i n f a c t e x i s t . An i n f r a r e d spectrum of the s o l i d was taken i n the manner described p r e v i o u s l y 4 , u s i n g KBr p l a t e s , on a Perkin-Elmer 421 spectrometer and i s compared t o KPO2F2, KSbF 6, S b F r O H - and (CH3) 2Sn(SbF 6) 2 below. TABLE 11 I n f r a r e d Spectra of Various Inorganic F l u o r i n e Compounds K P 0 2 F 2 KSbF 6 SbFcOH" 5 7 ( C H 3 ) 2 S n ( S b F 6 ) 2 ^ K SbF 5P0 2F 2 1332s v a Sym P 0 1310s V s y m PO 1148s 'asym 850 s & P F sym 83 2< 663 Sb-F 630 Sb-F 560 SsymPF2 503s 495s s = strong, m = medium, w = weak. 1210 w 990m Sb-F 910m Sb-F 828m 7* 2w 7 6 o v w 660s Sb-F 540 m 1317s v a s y m PO H ° 0 S ^sym PO 1020w 953m Sb-F 904m Sb-F 840m V S y m & ^asym PF 73 7 W 667s Sb-F 506m £ s v m P F 2 482 m I t appears t h a t i n the K S b F c P 0 2 F 2 spectrum ( c o l . 5) that the 97 i n f r a r e d spectrum of the POgFg g r o u P ( c o l . 1) can be di s c e r n e d , a l s o the band at 667 cra?^ can be assigned t o Sb-F s t r e t c h - ( c o l s . 58 2, 3, and 4 ) . I n ( C H ^ ) 2 S n ( S b F ^ ) 2 Goel has suggested that the medium i n t e n s i t y bands at 990 and 910 cm7^ are v i b r a t i o n a l modes, i n f r a r e d i n a c t i v e f o r the oc t a h e d r a l SbF^ i o n , which have become i n f r a r e d a c t i v e as a r e s u l t of d i s t o r t i o n of the SbF^~ group by the ( C H 3 ) 2 S n group. Of the remaining bands (1020w,• 953m, 904m and 737w) i n the KSbFrP02F2 spectrum the medium peaks at 953 and 904 cm7 are i n the same r e g i o n as the bands observed by Goel f o r the d i s -t o r t e d SbF^ and may be t e n t a t i v e l y assigned t o Sb-F v i b r a t i o n a l modes i n the SbF^ part of SbF^P02F2 . An x-ray powder photograph of the s o l i d was taken as des c r i b e d previously^" and v i s u a l com-parisons showed the obtained photograph to be q u i t e d i f f e r e n t from t h a t of KP02F2^ and KSbF^. I t thus appears t h a t the s o l i d product i s n e i t h e r KPOgFg nor KSbF^ nor a mixture of the two. To e s t a b l i s h f u r t h e r the species KSbF^PO?^ a sample was decomposed under vacuo at 250° i n a f l u o r i n a t e d n i c k e l can which was connected t o the simple vacuum l i n e shown i n F i g . 26. This c o n s i s t e d of two t r a p s f o l l o w e d by connections f o r a molecular weight bulb, an i n f r a r e d gas c e l l , and a manometer; f u r t h e r t r aps were i n c l u d e d before the r o t a r y pump. The gases evolved during the h e a t i n g of the can were condensed out i n the f i r s t t r a p ( -195°) which was then i s o l a t e d from the can. The l i q u i d n i t r o g e n bath was removed from the f i r s t t r a p and placed around the second which was then connected by- opening the stopcock t o the f i r s t t r a p . The contents of the f i r s t t r a p were allowed to warm to F i g . 26 Vacuum Line used f o r the Decomposition of KSbF c P0 oF~ Cr ft i M = molecular weight bulb I = i n f r a r e d gas c e l l N = n i c k e l can 9 9 room temperature and were condensed out i n the l i q u i d n i t r o g e n t r a p which was then disconnected from the f i r s t t r a p . The c o o l i n g bath was removed and the contents of the second t r a p were allowed t o warm up and expand i n t o the molecular weight bulb, i n f r a r e d -gas c e l l and the manometer. The procedure was repeated. The white s o l i d remaining i n the can a f t e r heating was i d e n t i f i e d as KSbF^ by i n f r a r e d (a s i n g l e broad band at 6 6 5 cm!""1" i n the r e g i o n 4 0 0 0 - 5 0 0 c m 7 \ c . f . l i t e r a t u r e value'' 9 of 6 6 0 crrC"*") and x-ray powder photograph ( i d e n t i c a l t o tha t of an authentic sample of KSbF^, s u p p l i e d by A l f a I n o r g a n i c s , I n c . ) . The r e s u l t s are c o n s i s t e n t w i t h the decomposition of KSbFrP02F2 according t o , KSbF 5P0 2F 2 , —> KSbF 6 + P0 2F ( 4 . 1 3 ) The i n f r a r e d of the gaseous sample was taken i n a c e l l w i t h C s l p l a t e s and a path l e n g t h of 9 0 nuns.. The pressure of the gas i n . the molecular weight bulb and the i n f r a r e d gas c e l l was of the order of 5 0 mms. of mercury. The molecular weight of the gaseous product(s) was found by two determinations to be 9 8 - 5 . The i n f r a r e d spectrum taken on the P e r k i n Elmer 4 2 1 spectrometer i s given i n Table 12 together w i t h t h a t of the rep o r t e d s p e c t r a of POF^^ and HPO2F2."*"2 I t would appear that the gas obtained i n « the f i r s t run i s POF^ (molecular weight, 1 0 4 ) w i t h p o s s i b l y some a S i F ^ i m p u r i t y . . S t a f f o r d remarks th a t i n h i s study of KP0 2F 2 at -1 1020 cm. the r e g i o n i s obscured by the S i F ^ s t r e t c h , thus the strong band observed at 1 0 2 9 cm."""'" may be due t o t h i s i m p u r i t y . On comparison of the second run w i t h the combined s p e c t r a of POF^ and HP0 2F 2 e x c e l l e n t agreement i s obtained. The most n o t i c e a b l e exception i s the band a l s o obtained i n both experiments. 1 0 0 T A B L E 1 2 I n f r a r e d Spectra of Gaseous Productts) From Decomposition of KSbF^P02F2 . HPO '2 F2 POF3 - Gaseous Productts) P0F, + HP0 9F Vapour at 0° C 1st Run 2nd Run 2 5 0 0 - • 3 1 0 0 mb 2 5 0 0 - 3 1 5 0 mb 2 5 0 0 --3IOO mb 1 4 1 5 ms . 1 4 1 6 s 1 4 1 6 s 1 4 1 6 ms 1 3 3 2 vs 1 3 3 2 s 1 3 3 2 vs 1 1 9 3 m 1 1 9 1 m 1 1 9 3 m 1 0 8 1 vs 1079 vs 1 0 8 1 vs 1 0 3 1 vvs / 1 0 3 6 m.sh 1 0 3 0 vs 1 0 3 1 vvs V1029 s 990 "vs 9 8 3 s 990 vs 9 9 3 s 9 8 6 vs 9 8 3 s 8 8 1 ms 8 8 0 ms 8 8 1 ms 8 7 3 ms •872 w 8 7 2 s 8 7 3 8 2 0 w 8 2 5 w 8 2 0 VI 7 3 2 s 7 2 8 ms 5 3 5 m 5 2 8 m 5 3 5 m 5 0 1 m 5 0 1 m 4 8 4 m 4 8 5 ms 490 msh 4 8 4 m 4 7 3 s 4 7 8 s 477 vs 473 s 4 6 7 4 5 6 at about 730 cm, 1 which has no corresponding absorption i n the 6l POF3-HPO2F2 composite spectrum. Corbridge and Lowe a s s i g n bands i n t h i s ' r e g i o n to P-F stretch, and re p o r t peaks at 721 cm."1, 728 cm."1 and 745 cm.'"1 f o r v a r i o u s monofluorophosphates. I t seems l i k e l y , t h e r e f o r e , t h a t some P-F species i s present whos.e remaining spectrum i s hidden by the POF^- - H P 0 ? F 2 bands. I t thus appears t h a t the complex decomposes t o the hexa-fluoroantimonate and gaseous phosphorus o x y - f l u o r i d e s , the major one being P O F 3. I t i s suggested t h a t the P O F 3 i s produced by f u r t h e r decomposition of P 0 2 F which a r i s e s according to (4.14). 3P0 2F -» P 0 F 3 + P 2 0 5 . (4.14) No d i r e c t evidence f o r P2P5 w a s obtained, however, i t I s l i k e l y t h a t i t would condense out i n the vacuum system (sublimes at 300°)^ and give l i t t l e i n d i c a t i o n of i t s presence i n the i n f r a -red s p e c t r a of the gaseous products and of the s o l i d l e f t i n the can. I n the second experiment the vacuum system w a s . c l e a r l y not p r o p e r l y d r i e d and the P 0 F 3 was hydrolyzed t o give the ob-served F i P 0 2 F 2 , a c c o r d i n g t o , P 0 F 3 + H 2 0 —> H P 0 2 F 2 + HF (4.15) H y d r o l y s i s of POgF may a l s o cause the pro d u c t i o n of monofluoro-phosphoric a c i d , •H2P03'F, u n f o r t u n a t e l y a. l i t e r a t u r e search y i e l d s no i n f o r m a t i o n on i t s i n f r a r e d spectrum. P 0 2 F + H 20 —> H 2 P 0 3F' (4-16) Another p o s s i b l e product of the decomposition of K S b F r - P 0 o F p i s P2O3FJ1 , however no evidence was obtained f o r i t s presence i n the gaseous products. CHAPTER V Nitrobenzene S o l u t i o n s 5.1 I n t r o d u c t i o n G i l l e s p i e et a l . showed that i n s u l p h u r i c a c i d the f o l -lowing order of a c i d strengths p r e v a i l e d , HSO^F> H2S0^CF^COOH > HPO^Fg and the r e s u l t s i n Chapter IV of the e l e c t r i c a l conduc-t i v i t y s t u d i e s of var i o u s a c i d s i n d i f l u o r o p h o s p h o r i c a c i d con-f i r m t h i s - o r d e r . A c i d i c behaviour has been mainly stu d i e d i n 1 19 p r o t o n i c media ' e.g. the s o l v e n t s H 20, HF, H2S0^, HC1, NH^ and CH^COOH; then to i n v e s t i g a t e f u r t h e r the f a c t o r s i n f l u e n c i n g the r e l a t i v e a c i d strengths of HP0 2F 2, H2S0^ and HSO^F d i l u t e s o l u -t i o n s of these a c i d s were studi e d i n a non-protonic medium. I t was decided to use nitrobenzene as the solvent as i t i s r e a d i l y a v a i l a b l e and has i t s e l f been s t u d i e d c o n d u c t i m e t r i c a l l y i n HSO^F, 1 0 H 2S0^ 1 9 and HP0 2F 2 ( t h i s work) and i s a s u i t a b l e solvent " f o r cryoscopic and e l e c t r i c a l c o n d u c t i v i t y experiments. I t was found t h a t i n HSO^F"^ as solvent nitrobenzene i s a strong base and i s f u l l y protonated whereas i n HgSO^ 2 and i n HF^ 9 i t i s a weak base. The r e a c t i o n between nitrobenzene and the in o r g a n i c a c i d s which provide the bulk solvent may be p i c t u r e d as i n v o l v i n g i n i t i a l formation of the adduct C^H^N02.HA foll o w e d by d i s s o c i a -t i o n i n t o i o n s , . . _ C 6H 5N0 2 + HA (C6H5N02.HA) C 6HrN0 2H + + A~ (5.1) A number of f a c t o r s may i n f l u e n c e the p o s i t i o n of t h i s e q u i l i b r i u m i t has been proposed t h a t the reason f o r the d i f f e r e n c e s I n the d i s s o c i a t i o n constants f o r these p o s t u l a t e d C^H^NO^.HA adducts i s 6 3 t h a t f l u o r o s u l p h u r i c a c i d i s a stronger acid. , or b e t t e r proton donor', than e i t h e r s u l p h u r i c a c i d or hydrogen f l u o r i d e . P r o p e r t i e of the bulk solvent such as i t s d i e l e c t r i c constant and i t s a b i l i t y to s o l v a t e the Ions produced are a l s o important f a c t o r s . Various workers have used nitrobenzene as a s o l v e n t because of i t s convenient f r e e z i n g p o i n t f o r cryoscopic s t u d i e s ; W h i t t l a ^ 4 has i n v e s t i g a t e d selenium t e t r a f l u o r i d e adducts i n nitrobenzene by e l e c t r i c a l c o n d t i c t i v i t y and cryoscopy. Taylor" 65 and Kraus s t u d i e d the e l e c t r i c a l c o n d u c t i v i t y of v a r i o u s p i c r a t e s and f u r t h e r work i n v o l v e d a study of substances which 66 f e l l i n t o three main c l a s s e s : ( i ) strong e l e c t r o l y t e s , ( i i ) weak e l e c t r o l y t e s and ( i i i ) weak e l e c t r o l y t e s i n which d i s -s o c i a t i o n i n t o f r e e a c i d and base takes place to a measurable extent. However, i t appears that l i t t l e has been done to study the e f f e c t s of strong i n o r g a n i c oxy-acids' i n . nitrobenzene by conductance and cryoscopy. One notable piece of work i s that of Oddo and A n e l l i who i n v e s t i g a t e d the depression of the f r e e z i n p o i n t caused by s u l p h u r i c and n i t r i c acid, i n a v a r i e t y of s o l -vents and they found t h a t i n nitrobenzene s u l p h u r i c a c i d e x i s t e d mainly i n the form of dimers whereas n i t r i c a c i d remained as the monomer. 5 . 2 Experimental A) Cryoscopy The c r y o s t a t shown i n F i g . 27 i s s i m i l a r t o t h a t used by Whittla"" 1-. A s i n g l e - h o l e cork was i n s e r t e d i n t o the B24.ground g l a s s socket and through t h i s . t h e platinum r e s i s t a n c e thermo-meter was lowered. . The thermometer was held at the d e s i r e d p o s i t i o n by pouring molten wax on the top of the cork and a l l o w ! 104 105 i t t o c o o l , i t was h e l d u p r i g h t by a s e m i - c i r c u l a r wire holder which f i t t e d i n t o the c r y o s t a t j u s t below the ground g l a s s socket. A l l ground g l a s s j o i n t s on the c r y o s t a t were greased, w i t h a narrow r i n g of s i l i c o n e grease (Dow-Corning). Temperatures were measured by a Leeds-Northrup capsule platinum r e s i s t a n c e thermo-meter which was c a l i b r a t e d by the N a t i o n a l Research C o u n c i l , Ottawa. The r e s i s t a n c e of the thermometer was determined on a G u i d e l i n e potentiometer (Leeds and Northrup, Type 43©3A) w i t h a standard 10 ohm r e s i s t a n c e (Leeds-Northrup). The c r y o s t a t c o n t a i n i n g the t e f l o n - c o a t e d , bar magnet s t i r r e r was connected to a d r y - a i r l i n e by means of the B19 cone and f l u s h e d out w i t h dry a i r f o r s e v e r a l hours. The cryo-s t a t was then t r a n s f e r r e d to the dry box and charged w i t h a weighed amount of nitrobenzene ( u s u a l l y of the order of 60g.). The cryo-s t a t was removed from the dry box and cooled i n a c o l d water bath ( 5 ° ) . At' temperatures below the f r e e z i n g point the r o t a t i o n of the magnetic s t i r r e r f r e q u e n t l y caused the solvent to 'seed-out', thus i t was necessary to d i s c o n t i n u e s t i r r i n g once the contents had cooled t o the f r e e z i n g p o i n t . The amount of supercooling xvas not allowed t o exceed 0 .5-0 .9° ( i f a l a r g e r amount of supercooling were allowed, the q u a n t i t y of s o l i d which separates would be so l a r g e t h a t the c o n c e n t r a t i o n of the s o l u t i o n would be g r e a t l y i n c r e a s e d and give erroneous values f o r the f r e e z i n g p o i n t de-68 p r e s s i o n ). The c o o l i n g bath was removed and the a i r jacket (J) was then placed around the lower part of the c r y o s t a t (C). The whole assembly was lowered i n t o a second ice/water bath, which was kept at 2-4° below the f r e e z i n g p o i n t of the nitrobenzene 106 s o l u t i o n . The magnetic s t i r r e r v/as s t a r t e d and i f f r e e z i n g d i d not occur the s o l u t i o n was seeded by adding a s m a l l piece of platinum p r e v i o u s l y cooled i n l i q u i d n i t r o g e n . Readings were taken on the potentiometer, u s i n g a moving c o i l galvanometer as a n u l l detector f o r f i f t e e n minutes a f t e r the s o l u t i o n was seeded out. As soon as n u c l e a t i o n takes place, the l a t e n t heat of c r y s t a l l i z a t i o n tends to r a i s e the tempera-t u r e . The temperature cannot r i s e above the f r e e z i n g p o i n t , but -i f the c o o l i n g i s too r a p i d i t may. w e l l never reach the t r u e m e l t i n g p o i n t . The f r e e z i n g point f o r the s o l u t i o n was c a l c u l a t e d from the maximum value observed w i t h the platinum r e s i s t a n c e t h e r -mometer. This value was a t t a i n e d three to four minutes a f t e r the s o l u t i o n was seeded out. The l i q u i d was allowed to warm up and the above procedure repeated. When r e p r o d u c i b l e values f o r the f r e e z i n g p o i n t of the pure s o l v e n t had been obtained the f i r s t a d d i t i o n of s o l u t e was made. During the remainder of the experiment the s o l u t i o n was not allowed to r i s e above 8°. The f r e e z i n g point of the s o l u -t i o n was determined i n the same manner as described f o r the pure s o l v e n t ; the amount of s u p e r - c o o l i n g was noted i n each case. For the a d d i t i o n s of s u l p h u r i c and f l u o r o s u l p h u r i c a c i d s weighed amounts of nitrobenzene and each a c i d were mixed i n weight-droppers i n the dry box. Great care was taken to ensure a homogeneous s o l u t i o n . The dropper was weighed by suspending i t from a s i n g l e pan balance and an a d d i t i o n of the acid/nitrobenzene mixture was q u i c k l y made to the c r y o s t a t through the B19 cone; 107 the dropper was then reweighed. The f r e e z i n g point of the r e s u l t -i n g s o l u t i o n was found i n the manner described p r e v i o u s l y . For every compound at l e a s t three a d d i t i o n s were made f o r each run and f o r each a d d i t i o n the depression of the f r e e z i n g point was checked at l e a s t t w i c e . A c o r r e c t i o n was made to the s o l u t i o n c o n c e n t r a t i o n f o r the amount of solvent f r o z e n out when the s o l u t i o n was seeded. The weight of nitrobenzene f r o z e n out Wn, i s given by the ex-. 64 p r e s s i o n , Wn = Ws Cp AT-AHf where Ws i s the weight of sol v e n t i n the c r y o s t a t , Cp the heat capacit}' of nitrobenzene (1 .52 gr^deg."! at 5°) , AT the amount of supe r c o o l i n g and AH^ the l a t e n t heat of f u s i o n of nitrobenzene (94.25 c a l . g," ). 7 The m o l a l i t y of the s o l u t i o n , m, i n e q u i l i -brium w i t h the s o l i d nitrobenzene was determined by the f o l l o w i n g equation, • m = . 1000 M T v ^ r where W i s the weight of s o l u t e and M i t s molecular weight. No c o r r e c t i o n was made f o r the heat c a p a c i t y of the c r y o s t a t . The s o l u t i o n s of the a c i d s i n nitrobenzene were found t o be unstable and darkened slc\-/ly; on standing f o r 24 hours the s o l u t i o n s turned b l a c k . The t o t a l time taken f o r each experiment was of the order of four t o s i x hours and the decomposition during t h i s time was not n o t i c e a b l e . W h i t t l a 0 ^ found t h a t during cryoscopic experiments l a s t i n g three t o four hours on selenium t e t r a f l u o r i d e adducts i n nitrobenzene the decomposition was sm a l l enough t o be neglected. B) E l e c t r i c a l C o n d u c t i v i t y The c o n d u c t i v i t y measurements were made i n nitrobenzene using the c o n d u c t i v i t y c e l l shown i n F i g . 2 . which was a l s o used f o r conductance s t u d i e s i n HPO2F2. The procedure f o l l o w e d was s i m i l a r t o th a t adopted f o r d i f l u o r o p h o s p h o r i c a c i d . The weighed c e l l was connected t o the d i s t i l l a t i o n apparatus ( F i g . 1) at K. P u r i f i e d nitrobenzene was added to the f i r s t d i s t i l l a t i o n f l a s k by means of a weight dropper. The apparatus was evacuated and the nitrobenzene was d i s t i l l e d under vacuo at a temperature of 40° i n t o f l a s k Y and f i n a l l y i n t o the c e l l . The pump was switched o f f and dry a i r was allowed t o enter the system. The c e l l was q u i c k l y capped, weighed and placed on a stand i n the o i l bath set at 2 5 ° . The a c i d s were added to the c e l l i n two ways; the f i r s t way i n v o l v e d the use of the microburette ( F i g . 4). The pure s o l u t e s and microburette were t r a n s f e r r e d to the dry box, where the b u r e t t e was r i n s e d out and then f i l l e d w i t h the s o l u t e t o be s t u d i e d . I t was then removed from the dry box and placed on the c e l l by means of the T e f l o n B19 socket adaptor. A d d i t i o n s were made by screwing up the plunger and r e c o r d i n g the volume a d d i t i o n s . The second way i n v o l v e d mixing known weights of the s o l u t e and nitrobenzene i n the dry box. The weight dropper was f i l l e d w i t h the r e s u l t i n g s o l u t i o n and reweighed. An a d d i t i o n was made to the c e l l and the dropper reweighed. I n both methods the s o l u t i o n s were mixed thoroughly a f t e r 109 each a d d i t i o n i n the c e l l and the c o n d u c t i v i t y recorded; the s o l u t i o n s were then mixed again and the c o n d u c t i v i t y redetermined u n t i l no f u r t h e r change was observed. I n t h i s way v a r i a t i o n s i n c o n d u c t i v i t y due to improper mixing were e l i m i n a t e d . As a c o n t r o l run the c o n d u c t i v i t i e s produced by s o l u t i o n s of t e t r a - n - b u t y l -ammonium bromide i n nitrobenzene were determined (Table 1 4 ) . The r e s u l t s agree w i t h l i t e r a t u r e values t o w i t h i n 2%. C) P r e p a r a t i o n of m a t e r i a l s AnalaR nitrobenzene was r e c r y s t a l l i z e d from i t s e l f twice and then s t o r e d over molecular s i e v e s , type 5^. I t was then doubly d i s t i l l e d twice under vacuo i n an apparatus s i m i l a r to that used f o r the p u r i f i c a t i o n of d i f l u o r o p h o s p h o r i c a c i d . The n i t r o -benzene was c o l l e c t e d i n a f l a s k which was q u i c k l y capped and t r a n s f e r r e d t o the dry box. Commercial b e n z i l was r e c r y s t a l l i z e d from alcohol'and was found t o have a melt i n g p o i n t of 94.7.-95.0°(95 ) . 5 . 3 R e s u l t s and D i s c u s s i o n The f r e e z i n g p o i n t of a l i q u i d i s lowered by the a d d i t i o n of a s o l u t e , and t h i s l o i t e r i n g i s d i r e c t l y p r o p o r t i o n a l t o the co n c e n t r a t i o n of the s o l u t i o n f o r d i l u t e s o l u t i o n s . AT = K fiA where AT I s the f r e e z i n g p o i n t depression, m the m o l a l i t y and Kf the molal f r e e z i n g p o i n t constant. I n cases where the s o l u t e d i s s o c i a t e s t o form more than one p a r t i c l e a more general ex-pr e s s i o n can be used, 110 AT = K f V m where V i s equal t o the number of p a r t i c l e s formed from each molecule of s o l u t e . The values obtained from the depression of the f r e e z i n g p o i n t are given i n Table 13 and i n F i g . 2$ AT, the f r e e z i n g point depression, i s p l o t t e d against c o n c e n t r a t i o n , m, expressed i n moles per 1000 g. of nitrobenzene. I t i s ap-parent t h a t the molal f r e e z i n g p o i n t constant, Kf, i s equal to the slope of the b e n z i l curve, assuming V" = 1. The value f o r Kf was found t o be 7.00 per 1000 g. which agrees w e l l w i t h repor-ted values by v a r i o u s workers (6.89-7.10°).^'"^ A) F l u o r o s u l p h u r i c a c i d s o l u t i o n s I t can be seen from F i g . 28 t h a t HSO^F a l s o appears to cause a depression of the f r e e z i n g p o i n t very near t o t h a t ex-pected f o r V - l corresponding to one mole of p a r t i c l e s per mole of a c i d i n the d i l u t e r e g i o n and s l i g h t l y l e s s , than one mole at the higher c o n c e n t r a t i o n s . I t was expected that HSO^F which has been described as the strongest simple ( i . e . i s o l a b l e ) a c i d known ^ would e x t e n s i v e l y protonate the nitrobenzene and thus cause twice the depression observed, because of the r e a c t i o n , HSO3F + C 6H 5N0 2 ~* C5HrN02H'r + SO3F" (5.2) Moreover, the e l e c t r i c a l c o n d u c t i v i t y r e s u l t s g iven i n Table 14 and p l o t t e d against the m o l a l i t y of the s o l u t i o n s i n F i g . 29 a l s o give no evidence f o r t h i s extensive p r o t o n a t i o n . U n f o r t u n a t e l y , the r e p r o d u c i b i l i t y of the c o n d u c t i v i t y r e s u l t s v/as not good, r e f l e c t i n g the f a c t t h a t the c o n d u c t i v i t y produced, by the s o l u t e i s so low that t r a c e s of Impurity which may have been present i n TABLE 13 Gryoscopic Measurements i n Nitrobenzene F l u o r o s u l p h u r i c A c i d T° A T 0 - • 10 2m T° A T 0 10 2m 5 . 6 9 7 ^ . 0 0 5 , 0 . 0 0 0 5 . 7 0 7 ^ . 0 0 5 0 . 0 0 0 5 . 2 0 1 - . 0 1 0 0 . 4 9 6 1 . 0 1 5 7 .172 5 . 1 5 1 - . 0 1 0 0 . 5 5 6 - . 0 1 5 8 . 1 7 7 4 . 4 7 9 7 . 0 4 5 I . 2 1 8 7 . O 5 O 1 8 . 2 1 4 . 5 4 3 x - 0 1 0 1.164~-.015 1 6 . 8 8 3 . 1 2 0 " - . 0 2 0 2 . 5 7 7 x . 0 2 5 3 9 . 0 2 4 . 0 6 2 ± . 0 2 0 1.645T-025 2 4 . 3 8 3 . 5 4 4 i . 0 2 0 2 . 1 6 3 7 - 0 2 5 3 1 . 8 9 2 . 4 7 7 - . 0 0 5 3 . 2 3 0 - . 0 1 0 4 8 . 8 O S u l p h u r i c A c i d T° A T 0 10 2m T° A T 0 10 2m 5 .73 6-.-015 0 . 0 0 0 5 . 7 3 6 i . 005 0 . 0 0 0 5 . 6 0 3 ± . 0 1 0 0 .133"- .025 2 .655 5 . 5 0 0 " i . 0 0 5 0 . 2 3 6 ± . 0 1 0 4 - 4 2 8 5 . 3 0 9 - . 0 1 0 0 . 4 2 7 - . 0 2 5 8 . 9 0 2 4 . 6 4 7 - . 0 1 0 0 . 8 8 9 - . 0 1 5 1 8 . 3 5 5 . 0 9 8 ^ . 0 1 5 0 . 6 3 8 * . 0 3 0 1 4 . 9 0 3 . 5 0 3 ^ . 0 4 0 2 . 2 3 3 - . 0 5 0 5 3 . 4 0 4 . 5 2 ± . 0 1 1 1 .154"-.026 2 4 . 5 5 T B e n z i l ° A T ° 10 2m T° A T ° 10 2m 5 . 6 9 2 ± . 0 2 0 0 . 0 0 0 5 . 7 0 7 ± . 0 0 5 0 . 0 0 0 5 . 6 3 3 ± . 0 2 0 0 . 0 5 9 - . 0 4 0 0 . 9 9 7 8 5 .657 J -" .005 0 . 0 5 0 ± . 0 1 0 I . O 8 4 5 . 5 6 4 ^ . 0 0 5 0.1281". 025 2 . 0 5 4 5 . 3 2 4 ± . 0 1 4 0 . 3 83 ± . 0 1 9 5 .675 5 . 3 9 7 ± . 0 0 5 0 . 2 9 5 ± . 0 2 5 4 . 9 0 4 4 . 9 8 5 ± . 0 0 0 0 . 7 2 2 ± . 0 0 5 1 0 . 5 3 4 . 4 3 0 ± . 0 0 5 1.277±.010 1 8 . 1 3 T i s the average value of the f r e e z i n g p o i n t A T 0 i s the average value of the f r e e z i n g p o i n t depression caused by the a d d i t i o n of s o l u t e m i s the co n c e n t r a t i o n of the s o l u t e expressed i n moles per 1000 g. of nitrobenzene F i g . 28 Depression of Freezing P o i n t (AT) f o r Various Solutes i n Nitrobenzene 0 ' ' 10 20 . 3 0 10 2 x m o l a l i t y , m the s o l u t e , or produced by minor s i d e r e a c t i o n s between s o l u t e and s o l v e n t , or may have entered the s o l u t i o n during h a n d l i n g , a f f e c t the r e s u l t s t o a considerable degree. Nevertheless i t i s p o s s i b l e t o estimate the equivalent c o n d u c t i v i t i e s produced by s o l u t i o n s of HSO^F and these are presented i n Table 15. The u n c e r t a i n t y i n the va l u e s , given i n brackets, was determined from the e x p e r i -mental s c a t t e r . .In s p i t e of the approximate nature of these eq u i v a l e n t c o n d u c t i v i t y values i t i s c l e a r that they are lower even than those obtained f o r weak e l e c t r o l y t e s such as t r i m e t h y l -hydroxyammonium p i c r a t e which has a d i s s o c i a t i o n constant of 1.7 x 10~^ mole 17"^ i n ni t r o b e n z e n e . 0 ^ From the r e s u l t s i t may be concluded that HSO^F d i s s o l v e s i n nitrobenzene e s s e n t i a l l y as a n o n - e l e c t r o l y t e . I f any d i s -s o c i a t i o n occurs the d i s s o c i a t i o n constant i s probably l e s s than r i 10 2 x 10 J moles 1. . When HSO^F provides the bulk solvent , however, the d i s s o c i a t i o n i s so extensive t h a t the e q u i l i b r i u m constant cannot be measured. Since d i s s o c i a t i o n constants as 2 -1 high as 1.3 x 10 moles 1. have been measured i n HSO^F i t i s reasonable t o assume th a t the d i s s o c i a t i o n constant of n i t r o -2 benzene In t h i s a c i d s olvent i s greater than 2 x 10 . Hence, 7 the d i s s o c i a t i o n constant decreases by a f a c t o r of 10' i n going from s o l u t i o n s i n f l u o r o s u l p h u r i c a c i d to s o l u t i o n s i n nitrobenzene. Nitrobenzene has a d i e l e c t r i c constant of 34.5 and that of HSO.-jF has been estimated to be 120,"^ thus the d i f f e r e n c e i n the d i e l e c t r i c constants w i l l account t o some extent f o r the d i f -ference i n the d i s s o c i a t i o n constants observed. The e f f e c t may 114 TABLE 12, S p e c i f i c Conductances of Some E l e c t r o l y t e S o l u t i o n s i n Nitrobenzene at 25° Tetra-n-butylammonium bromide io 2 : m 0.000 0.6194 0.8927 1.214 1.513 0.0000 0.04980 0.09618 0.1663 0.2385 0.3153 0.3941 l O ^ ohrfl-lcmr-'-4.607 1766 2354 2969 3533 2.644 182.9 343.5 563.5 775.4 992.8 1205 HP0 2F 2(microburette) uncorrected 0.000 9.274 3.847 24.92 7.617 33.49 13.31 41.57 19.08 43.45 26.77 40.34 34.85 36.50 42.16 34.73 i n s o l u b l e F l u o r o s u l p h u r i c a c i d (microburette) 102m 0 4 9 13 22 31 39 48 60 72 84 (HSOoF ^0 0 0 0 0 1 5 16 36 81 .000 .580 .119 .61 .49. .21 .76 .18 .52 .55 .28 / n i t r o b e n .0000 .06478 .1920 .4311 .8207 .441 .550 .68 .95 .06 1 0 7X ohm-lcmrl 6.979 • 29.60 63.59 107.2 206.9 332.2 476.8 638.6 917.2 1232 1588 zene s o l u t i o n ) IO .64 15.12 25.68 33-44 31.99 50.89 114 .7 205.9 480.7 1504 TABLE 14 (cont'd) H-SO, ( s o l u t i o n ) H?SO, (microburette) 102m 10 7X 102m 10 7X ohm- cm. ohm-lcmrl 0.000 • 8.326 0.000 3.302 0.05473 10.97 5.450 292.9 0.1375 16.92 8.022 359.8 . 0.1899 26.47 10.57 416.1 0.3293 39.66 15.49 504.7 0.5175 57.43 20.98 593.5 0.7729 81.84 29.26 698.9 1.410 105.0 39.39 800 .8 2.347 152.0 51.49 832.3 5.361 231.5 65.84 -944.5 9.847 343.1 82.41 988.7 18.00 537.5 97.75 1062 34.02 1011 . Q 43.85 1376 EF. 0.000 5.964 0.000- 3.71 0.7123 40.72 27.5 914 1.893 77.07 46.2 1650 2.938 108.1 58.4 2950 4.676 155.4 7.499 238.3 11.60 369.4 18.28 655.9 28.28 812.2 46.72 1032 63.67 1210 87.57 1516 A d d i t i o n of 0.0277 g-of water (0.0267 molal) causedX to approximately double F i g . 29 S p e c i f i c C o n d u c t i v i t i e s of Some Solutes i n Nitrobenzene at 25 ( 1 . 025OCH I to B o 2000+ - 4 - 500 t e t r a n-butylammonium bromide .10 2 20 10 x m o l a l i t y , m 30 uo be estimated on a p u r e l y e l e c t r o s t a t i c b a s i s . The e l e c t r i c a l f r e e energy f o r a p a i r of ions of charge +e and -e separated by a d i s t a n c e r i n a medium of d i e l e c t r i c constant €, i s given by, F - e 2 / r e o Assuming a value of 2A f o r r and values of € equal t o 120 and 34-5 f o r € H S Q F and 6 ^ ^ ^ r e s p e c t i v e l y , the f r e e energy 3 6 5 2 d i f f e r e n c e , A F , f o r the two ions i n the d i f f e r e n t media i s 3400 cal./mole. On t h i s b a s i s the r a t i o of the e q u i l i b r i u m constants i n the two media would be - A F / R T " K 2 The d i e l e c t r i c constants used are the bulk d i e l e c t r i c constants f o r the l i q u i d s and are s t r i c t l y an approximation f o r the values i n the immediate v i c i n i t y of the ion s . I t seems l i k e l y t h a t the bulk d i e l e c t r i c constant of HSO3F i s enhanced g r e a t l y by the a s s o c i a t e d nature of the l i q u i d and hence i s probably c l o s e r t o t h a t of nitrobenzene i n the v i c i n i t y of the i o n s . This would 2 mean t h a t the value 3 x 10 c a l c u l a t e d above i s too lar g e and thus i t may be concluded that the l a r g e f a c t o r of 10? a c t u a l l y observed f o r the r a t i o of the e q u i l i b r i u m constants i s only p a r t i a l l y accounted f o r by the d i f f e r e n c e s i n the d i e l e c t r i c constants of the two rnedia>. More important i s the f a c t t h a t the SO-^F i o n i s s t a b i l i z e d i n HSO^F a c i d s o l u t i o n s through strong hydrogen bonding to the sol v e n t molecules. Such s t a b i l i z a t i o n i s not p o s s i b l e i n the non-protonic s o l v e n t , nitrobenzene. B) Sulphuric a c i d s o l u t i o n s i n nitrobenzene The cryoscopic values (Table 13) show that l e s s than 118 TABLE 15 E q u i v a l e n t C o n d u c t i v i t i e s 10 2m 0.4170 0.8340 1.668 4.170 8.340 16.68 20.85 25.02 33.36 41.70 H 2 S 0 4 10 2C 0.500 1.00 2.00 5.00 10.0 2 0 . 0 25.0 3 0 . 0 4 0 . 0 50.0 HSO^F IOTK. >A ) 50 1.0 ( 0 . 4 70 0 . 7 0 ( 0 . 2 ) 90 0.45(0.2 ) 180 O .38 (0.1 ) 315 0.32 (0.1 ) 540 0.26 (0 . 0 3 ) 620 0.24 (0 . 0 3 ) 720 0.23 (0 . 0 3 ) 855 0.21 (0 . 0 3 ) 965 0.19 (0 . 0 3 ) 0 . 4170 0.500 20 0.40 ( 0 . 2 ) 0 . 8340 1.00 30 0.25 ( 0 . 1 ) 1. 668 2.00 40 0 .20 (0 .1) 4 . 170 5.00 65 0.12 (0 .04) 8. 340 10.0 100 0.10 (0 .04) 16. 68 2 0 . 0 170 0 . 0 8 5 ( 0 . 0 2 ) 20. 85 25.0 210 0 .081(0.01) 25. 02 3 0 . 0 275 0 . 0 8 0 ( 0 . 0 0 7 ) 33 . 36 4 0 . 0 390 0.093'( 0.007) 4 1 . 70 50.0 525 0.11 Tetra-n-butylammonium bromide 2 .10 C. v A 0.05969 30.64 0.1153 29.79 0.1993 28.27 0.2858 27.13 0.3779 26.27 0.4723 25.50 Tetra-n-butj'-laramonium bromide 66 10 2C ; 0.005260 0.01284 0.03268 O .O8I84 0.2142 0.5515 , K= l 6 2 x l 0 ~ 4 mo TV 32.88 32.44 31.67 30.39 28.24 25.12 l e s / l i t r e Trimethylhydroxyammoniurn p i c r a t e 65 0.003178 0.007591 0.01802 0.03760 0.08016 0.1750 0.4329 17.19 12.64 8.960 6.554 4.688 3.292 2.17' K= 0 . 1 7 x l 0 ~ 4 m o l e s / l i t r L i t h i u m p i c r a t e 66 0.1091 0.2671 0.5754 0.7782 0.9362 1.074 0.1574 O . I367 0.1237 0.1132 0.1080 0.0994 K-0.0006x10"*- m o l e s / l i t r e Fig.- 30 Equivalent C o n d u c t i v i t i e s of Some E l e c t r o l y t e s in| Nitrobenzene at 25° < .21 •P •H > •H -P O 0 O O C CO o o O H 2 S 0 ^ • HSO^F A l i t h i u m p i c r a t O t r i m e t h y l h y -droxy-ammonium p i c r a t e 10 C: one mole of p a r t i c l e s are produced per mole of s u l p h u r i c a c i d molecules over the co n c e n t r a t i o n range studied. The H^SO^ curve i n F i g . 28 has a slope of 4-66 which i s cons i d e r a b l y l e s s than t h a t expected f o r a n o n - e l e c t r o l y t e and i t would appear that some d i m e r i z a t i o n of the H^SO^ molecules occurs. An examination of the chemical and p h y s i c a l p r o p e r t i e s of the a c i d s , H^SO^ and HSO^F, i n d i c a t e s t h a t s u l p h u r i c a c i d i s much more e x t e n s i v e l y hydrogen bonded ( i . e . associated) than f l u o r o s u l p h u r i c a c i d and i t i s thus not s u r p r i s i n g t h a t t h i s tendency towards a s s o c i a t i o n i s e x h i b i t e d 'to a l a r g e r degree by HgSO^ i n nitrobenzene. As was found i n the case of the f l u o r o s u l p h u r i c a c i d s o l u t i o n s the r e p r o d u c i b i l i t y of the c o n d u c t i v i t y values was poor (Table 11+). I t i s immediately apparent that, compared to the f a i r l y strong e l e c t r o l y t e tetrabutylammonium bromide, J^SO^ l i k e HSO^F appears t o be a very weak e l e c t r o l y t e . The i n t e r p r e t a t i o n of the con-d u c t i v i t y data f o r s u l p h u r i c a c i d i s complicated by the f a c t t h a t the a c i d i t s e l f undergoes r a t h e r extensive and complicated s e l f d i s s o c i a t i o n r e a c t i o n s and i t i s d i f f i c u l t to p r e d i c t what e f f e c t the nitrobenzene w i l l have on these. Nevertheless, i t i s c l e a r from the estimated equivalent c o n d u c t i v i t y values f o r the a c i d (Table 15) t h a t the degree of d i s s o c i a t i o n i n t o i o n s i s not much gre a t e r than t h a t observed f o r the f l u o r o s u l p h u r i c a c i d s o l u t i o n s and i t i s reasonable to conclude that no s i g n i f i c a n t d i s s o c i a t i o n according t o C 6 H 5 N 0 2 - H A ^ C 6 H 5 N 0 2 H + + A " ^.?>) takes p l a c e . Ignoring the sm a l l degree of d i s s o c i a t i o n i n t o ions the cryoscopic V values may be i n t e r p r e t e d i n terms of the r e a c t i o ( H 2 S 0 4 ) 2 ^ 2H 2S0 4 w i t h an e q u i l i b r i u m constant of approximately 1.5 x 10"^ mole kg. I t i s evident t h a t i n s o l u t i o n s of nitrobenzene the a c i d s t r e n g t h of s u l p h u r i c a c i d r e l a t i v e to the base nitrobenzene has been reduced not only to the extent that there i s no s i g n i f i c a n t p r o t o n a t i o n of nitrobenzene but a l s o (as i s shown by the observa-t i o n t h a t approximately h a l f of the s u l p h u r i c a c i d molecules are present as dimers) to the extent t h a t the nitrobenzene i s i n com-p e t i t i o n w i t h other molecules of H2SO4 f o r forming hydrogen-bonded adducts. An e a r l i e r r e p o r t that s u l p h u r i c a c i d i s com-p l e t e l y dimerized i n nitrobenzene s o l u t i o n s was not confirmed i n t h i s work. C) D i f l u o r o p h o s p h o r i c a c i d s o l u t i o n s I n the case of HP0pF2, the a c i d and nitrobenzene were found to be i m m i s c i b l e and only at the lowest concentrations d i d d i s s o l u t i o n appear t o be complete (at a c o n c e n t r a t i o n of l e s s -than 0.1 m o l a l ) , whereas H 2S0^ and HSO^F d i s s o l v e r e a d i l y . The e l e c t r i c a l c o n d u c t i v i t i e s observed f o r the HPOgFg/nitrobenzene s o l u t i o n s were s m a l l and q u i c k l y l e v e l l e d o f f at a value of -7 1 - 1 43 x 10 ' ohms "cm. . The data f o r the c o n d u c t i v i t y s t u d i e s f o r HF/nitrobenzene s o l u t i o n s obtained by other workers cite a l s o given i n Table 14 and i t i s i n t e r e s t i n g t o note t h a t at low concentra-t i o n s the s p e c i f i c c o n d u c t i v i t y i s of the same order as that f o r the i n o r g a n i c a c i d s s t u d i e d i n t h i s work. 5.4. Conclusion The a c i d s trengths of HSO3F and H 2S0^ d e f i n e d i n terms of t h e i r a b i l i t y t o protonate bases depends to a l a r g e degree on the nature of the solv e n t . I n bulk, where the ac i d s themselves provide the p r o t o n i c medium, or i n s o l u t i o n i n other p r o t o n i c s o l v e n t s these a c i d s are indeed s t r o n g ; however, t h e i r strengths may be co n s i d e r a b l y reduced i n media where there i s no- s t a b i l i -z a t i o n by hydrogen bonding to sol v e n t molecules of the anion pro-duced by the p r o t o n a t i o n r e a c t i o n . The importance of anion s t a b i l i z a t i o n by hydrogen bonding t o solvent molecules i n det e r -mining the apparent strengths of a c i d s was r e c e n t l y mentioned 71 elsewhere.' Although HSO3F and HgSO^ do not e x h i b i t a c i d behaviour i n d i l u t e s o l u t i o n s i n nitrobenzene i n the sense of protonating nitrobenzene molecules the f a c t t h a t the a c i d s are s o l u b l e i n -d i c a t e s r a t h e r weak, a c i d behaviour of these s o l u t e s towards nitrobenzene. I n order f o r these a c i d s to be s o l u b l e t h e i r ex-t e n s i v e hydrogen bonded s t r u c t u r e s must be destroyed and t h i s , presumably, i s due t o i n t e r a c t i o n between the a c i d molecules and the nitrobenzene molecules i n the form of hydrogen bonding between the two (a type of weak acid-base r e a c t i o n ) . The f a c t that HPO2F2 i s e s s e n t i a l l y i n s o l u b l e i n nitrobenzene suggests t h a t HPO2F2 i s not able to form strong hydrogen bonds w i t h nitrobenzene molecules and thus i n d i c a t e s t h a t even i n non-protonic media d i f l u o r o p h o s -phoric a c i d i s a weaker a c i d than e i t h e r HoS0, or HS0 oF. 123 CHAPTER VI Summary and Suggestions f o r Further Work 6.1 Summary From the i n v e s t i g a t i o n of the e l e c t r i c a l c o n d u c t i v i t i e s of s o l u t i o n s of the a l k a l i and a l k a l i n e earth metal d i f l u o r o -phosphates i n HPO2F2 ^ w 0 models were proposed t o e x p l a i n the r e s u l t s : ( i ) complete, d i s s o c i a t i o n w i t h weak s o l u t e - s o l v e n t i n t e r a c t i o n and ( i i ) incomplete d i s s o c i a t i o n w i t h the l i t h i u m s a l t e x h i b i t i n g the g r e a t e s t degree of d i s s o c i a t i o n of the a l k a l i metal difluorophosphates. Of the two models, the l a t t e r i s pre-f e r r e d . Nuclear magnetic resonance s t u d i e s of a l k a l i metal d i -fluorophosphate s o l u t i o n s tend t o s u b s t a n t i a t e t h i s preference, e s p e c i a l l y the 1°F chemical s h i f t s which are small and t o l o w - f i e l d . I t i s probable t h a t i f difluorophosphates are f u l l y d i s s o c i a t e d then the presence of a l a r g e c o n c e n t r a t i o n of POgFg" ions would r e s u l t i n chemical s h i f t s to h i g h - f i e l d due t o i n -creased s h i e l d i n g of the f l u o r i n e n u c l e i . V arious bases were a l s o s t u d i e d c o n d u c t i m e t r i c a l l y i n HPO2F2. Organic amines gave c o n d u c t i v i t i e s of the same order as that e x h i b i t e d by CsP0 2F2 s o l u t i o n s , thus suggesting t h a t complete d i s s o c i a t i o n of the amines does not occur. Several of the organic compounds i n v e s t i g a t e d proved t o be v i r t u a l l y i n s o l u b l e . I n -organic bases were a l s o examined; the a l k a l i and a l k a l i n e earth metal c h l o r i d e s gave c o n d u c t i v i t i e s s i m i l a r t o those given by the corresponding difluorophosphates thus suggesting that the c h l o r i d e s undergo complete s o l v o l y s i s and the HC1 produced i s a n o n - e l e c t r o l y t e i n HPO2F2. Of the c h l o r i d e s s t u d i e d tetraphenylarsonium c h l o r i d e gave the highest c o n d u c t i v i t y which i s i n d i c a t i v e of l a r g e c a t i o n s e x h i b i t i n g the le a s t ' i o n - p a i r i n g and greatest c o n d u c t i v i t y i n a medium of low d i e l e c t r i c constant. S o l u t i o n s of SbF^, HSO^F and HgSO^ were i n v e s t i g a t e d c o n d u c t i m e t r i c a l l y i n HPO2F2 and i t was concluded that these s o l u t e s are a c i d s and can be t i t r a t e d w i t h base. I n each case the s a l t produced by the t i t r a t i o n was i n s o l u b l e and was i s o l a t e d . The i n s o l u b i l i t y of these s a l t s e.g. K S b F ^ P 0 2 F 2 , KSO^F and KHSO^ lends f u r t h e r support t o the proposal t h a t HPO2F2 has a low d i -e l e c t r i c constant. Nuclear magnetic resonance s t u d i e s of the SbF^ / H P 0 2 F 2 s o l u t i o n s were a l s o examined and i t was found that the expected species, H S b F r ) P 0 2F 2 could be i d e n t i f i e d i n the var i o u s s p e c t r a ; other antimony p e n t a f l u o r i d e — d i f l u o r o p h o s p h a t e com-plexes are proposed to e x p l a i n the remaining peaks i n the spectra. An attempt was.made t o i d e n t i f y f u r t h e r the species SbF^POgFg" by decomposing KSbF^ P 0 2F 2, however, of the expected products, PO2F and KSbF^, only the hexafluoroantimonate was found. S o l u t i o n s of HgSO^, H P 0 2 F 2 and HSO^F were a l s o s t u d i e d i n nitrobenzene t o i n v e s t i g a t e f u r t h e r the f a c t o r s a f f e c t i n g r e l a t i v e a c i d strengths of pro t o n i c a c i d s . E l e c t r i c a l conduc-t i v i t y s t u d i e s showed t h a t HgSO^ and HSO^F were s o l u b l e and were v i r t u a l l y n o n - e l e c t r o l y t e s whereas H P 0 2 F 2 was only s l i g h t l y s o l u b l e . Cryoscopic i n v e s t i g a t i o n s of the HgSO^ and HSO^F s o l u t i o n s i n nitrobenzene i n d i c a t e t h a t HSO^F e x i s t s e s s e n t i a l l y as a monomer whereas H 2 S 0 , e x i s t s i n a polymeric form. 6.2 Suggestions f o r f u r t h e r work As has been mentioned p r e v i o u s l y , a knowledge of the d i -e l e c t r i c constant of HPC^Fg would be of great value i n the i n t e r -72 p r e t a t i o n of the c o n d u c t i v i t y data. G i l l e s p i e et a l . have r e -ported on the problems of measuring the d i e l e c t r i c constant of conducting and v i s c o u s l i q u i d s e.g. s u l p h u r i c , n i t r i c and c h l o r o -s u l p h u r i c a c i d s . The " f o r c e " method of determining the s t a t i c d i e l e c t r i c constant was used and u n f o r t u n a t e l y apparatus of t h i s type i s not a v a i l a b l e i n these l a b o r a t o r i e s . I t a l s o w i l l be necessary to undertake the' measurement of t r a n s p o r t numbers to determine whether abnormal c o n d u c t i v i t y occurs i n the solvent and to what extent i o n s other than the a u t o p r o t o l y s i s ions c a r r y the 55 c u r r e n t . However, i f the method used by Thompson ' i s employed, the a n a l y t i c a l problems of measuring small changes i n concentra-t i o n i n the anode and cathode compartments of the t r a n s p o r t number c e l l w i l l have to be solved. Cryoscopy has proved very u s e f u l i n the i n v e s t i g a t i o n of ^2^4 a n d HSO-jF s o l u t i o n s when used i n c o n j u n c t i o n w i t h conduc-t i v i t y . I n f o r m a t i o n regarding degrees of d i s s o c i a t i o n of v a r i o u s e l e c t r o l y t e s i n these media can be obtained. The cryoscopic constant f o r HPOgFg i s not known and would have to be determined, otherwise only r e l a t i v e extents of d i s s o c i a t i o n could be found but t h i s would s t i l l be u s e f u l i n the i n t e r p r e t a t i o n of the con-d u c t i v i t y r e s u l t s of a l k a l i metal difluorophosphates. • I t has been confirmed t h a t HP02F2 i s a weaker a c i d than both H0SO1 and HSOoF a n d - i t would be i n t e r e s t i n g t o attempt a 126 determination of the Hammet a c i d i t y f u n c t i o n Ho f o r HPOgFg. I t i s l i k e l y t h a t AsF^ and BF^ w i l l a l s o prove t o be ac i d s i n HPO2F2 and t i t r a t i o n of these a c i d s w i t h KPO2F2 may y i e l d i n s o l u b l e s a l t s of composition KBF 3P0 2F 2 and KAsFr_P02F2. As a l k a l i n e earth and a l k a l i metal difluorophosphates have now been prepared i t would be of i n t e r e s t to attempt the p r e p a r a t i o n of t r a n s i t i o n metal difluorophosphates by r e a c t i o n of the t r a n s i t i o n metal c h l o r i d e s w i t h d i f l u o r o p h o s p h o r i c a c i d . 1 2 7 BIBLIOGRAPHY 1. H. H. S i s l e r , 'Chemistry i n Non-Aqueous Solvents', Rheinhold, New York (1964). 2. W. E. White and C. Pupp, Encyclopedia of Chem. Tech., 9 , 635 (1966). 3. R. Schmutzler, 'Advances i n F l u o r i n e Chemistry', 5.> 18? (I965). Eds. M. Stacey, J . C. Tatlow and A. G. Sharpe, Butterworths, London. 4. W. Reed, M.Sc. Thesis, U n i v e r s i t y of B r i t i s h Columbia, Vancouver (1965). 5. W. Lange, Ber., 62B, 786 (1929) . 6. R. W. H a r r i s o n , R. C..Thompson and J . T r o t t e r , J . Chem. Soc. (A), 1775 (1966) . J . T r o t t e r and 3. H. Whitlow, J . Chem. Soc. (A), I383 (1967) . 7. F. A. Cotton and G. W i l k i n s o n , 'Advanced Inorganic Chemistry', I n t e r s c i e n c e , p. 124 (1962). 8 . 'Handbook of Chemistry and P h y s i c s ' . 4 6 t h . E d i t i o n , Chemical Rubber Co., Ohio (1966) . 9 . A. S. L e n s k i i , R. D. Shaposhnikova and A. S. A l l i l u e v a , Zh. P r i k l . Khirn., 3_5_, 760 (1962) . 1 0 . J . Ba r r , R. J . G i l l e s o i e and R. C. Thompson, Inorg. Chem., 2 , 1149 (1964). 11. S. Glasstone, ' P h y s i c a l Chemistry', MacMillan, London (i960). 12. S. M. Chackalackal and F. S t a f f o r d , J . Am. Chem. S o c , 88, 4815 (1966) . 13. W. J . Moore, ' P h y s i c a l Chemistry', P r e n t i c e - H a l l , Englewood C l i f f s , p. 422 (I960). 14-. J . A. Pople, W. G. Schneider and H. J . B e r n s t e i n , 'High-R e s o l u t i o n Nuclear Magnetic Resonance', McGraw-Hill, New York, p. 400 (1959) . 15. T. M o e l l e r , 'Inorganic Chemistry', Wiley, New York (1952) . 16. E.' C. F r a n k l i n , J . Am. Chem. S o c , 46, 2137 (1924). 17. A. F. 0 . Germann, J . Am. Chem. S o c , 47, 246I (1925). 18. H. P. Cady and H. M. E l s e y , J . Chem. Ed., £, 1425 (1928). 128 19. R. J . G i l l e s p i e and E. A. Robinson, 'Non-Aqeous Solvent Systems', Ed. T. C. Waddington, Academic Pr e s s , New York (1965). 20. J . H. Simons, ' F l u o r i n e Chemistry', 1, 225, Academic P r e s s , New York (1950) . 21. R. J . G i l l e s p i e and J . A. L e i s t e n , Quart. Rev. (London), 8, 40 (1954). E. M. A r n e t t , ' P h y s i c a l Organic Chemistry', 1, 223, I n t e r s c i e n c e , (1963). 22. J . B a r r , R. J . G i l l e s p i e and E. -A. Robinson, Can. J . Chem., 2 9 , 1266 (I96.I). 23. G. Jones and D. B o l l i n g e r , J . Am. Chem. S o c , _5_7, 280 (1935). 24. J . L i n d , J . Zwolenik and R. Fuoss, J . Am. Chem. S o c , 81, 1557 (1959). 25. A. C. Harkness and H. M. Daggett, Can. J . Chem., 1215 (1965). 26. . D. P. Shoemaker and C. W. Garlend. 'Experiments i n P h y s i c a l Chemistry', McGraw-Hill (1962). 27. R. A. Robinson and R. H. Stokes, ' E l e c t r o l y t e S o l u t i o n s ' , Butterworths, London (1955)• 28. L. S. Darken and H. F. Meier, J . Am. Chem. S o c , 64, 621 (1942) 29. S. J . Bass and R. J . G i l l e s p i e , J . Chem. S o c , 814 (I960). 30. C. V/. Davies, 'Ion A s s o c i a t i o n ' , Butterworths, London (1962). 31. J . Lewis and R. G. W i l k i n s , 'Modern Coordination Chemistry', I n t e r s c i e n c e , New York (196/).). 32. J . L. Kavanau, 'Water and Solute-Water I n t e r a c t i o n s ' , Holden-Day, San F r a n c i s c o (1964). 33. R. J . G i l l e s p i e and R. F. White, Can. J . Chem., 3_8, 1371 (I960) 34. T. B i r c h a l l and R. J . G i l l e s p i e , .unpublished experiments 3 5 . W. G. Schneider, H. J . B e r n s t e i n and J . A. Pople, J.'Chem. Phys., 28, 6Q1 (1958). 36. J . C. Hindman, J . Chem. Phys., 36, 1000.(1962). 37. R. J. G i l l e s p i e , Rev. Pure and Appl. Chem., £, 1 (1959). 129 38. R. J . G i l l e s p i e and S. Wasif, J . Chem. S o c , 215 (1953). 39. B. B. Owen and S. R. B r i n k l e y , Chem. Rev., 29, 46I (1942). 40. R. H. Flowers, R. J . G i l l e s p i e and E. A. Robinson, J . Chem. . Soc., 845 (I960). 41. A. M. Couture and K. J . L a i d l e r , Can. J . Chem., 3_4, 1209 (1956) 42. R. J . G i l l e s p i e , J . B. Mil n e and J . B. Senior, Inorg. Chem., £, 1233 (1966). 43. R. H. Flowers, R. J . G i l l e s p i e and E. A. Robinson, Can. J . Chem. , j[8, 1363 (I960). 44. R. J . G i l l e s p i e , J . V. Oubridge and C. Solomons, J . Chem. S o c , 1804 (1957). 45. D. V/. A. Sharp, J . Chem. S o c , 3761 (1957). 46. A. F. C l i f f o r d and S. Kongpricha, J . Inorg. Nuclear Chem., 1, 76 (1957). A. F. C l i f f o r d and A. G. M o r r i s , i b i d . , - 5, 71 (1957). 47. M. K i l p a t r i c k and T. J . Lewis,. J . Am. Chem. S o c , 78, 5186 (1956). 48. H. H. Hyman, L. A. Quarterrnan, M. K i l p a t r i c k and J . J . Katz, J . Phys. Chem., 65, 123 (1961). 49. H. H. Hyman and J . J . Katz, 'Non-Aqueous Solvent Systems', Ed. T. C. Waddington, Academic Press, New York (1965). 50. R. J . G i l l e s p i e and K. C. Moss, J . Chem. Soc. (A), 1171 (1966). 51. A. A. Woolf, J . Chem. S o c , 433 (1955) 52. J . Ba r r , Ph. D. Thesis, U n i v e r s i t y of London, London, England (1959). 53. R. C. Thompson, J . B a r r , R. J . G i l l e s p i e , J . B. Mil n e and R. A. Rothenbury, Inorg. Chem., 4_, I64I (1965). 54- D. D. Ames, S. Ohashi, C. F. C a l l i s and J . R. Van Wazer, J . Am. Chem. S o c , 81, 6350 (1959). 55. R. C. Thompson, Ph. D. Thesis, McMaster U n i v e r s i t y , Hamilton (1962). 56. C. J . Hoffman, B. E. Holder and W. L. J o l l y , J . Phys. Chem., 62, 364 (1958). 130 5 7 . L. K o l d i t z and. B. Nussbue c k e r , Z. Anorg. A l l g e m . Chem. , 3 J 7 , 191 ( 1 9 6 5 ) . 5 8 . R. G. G o e l , Ph. D. T h e s i s , U n i v e r s i t y o f B r i t i s h C o l u m b i a , Vancouver (I . 9 6 5 ) . 5 9 . S. P. B e a t o n , Ph. D. T h e s i s , U n i v e r s i t y o f B r i t i s h C o lumbia, Vancouver ( 1 9 6 6 ) . 6 0 . H. S. Gutowsky and A. D. L i e h r , J . Chem. Phys., 20, 1652 (1952) 6 1 . D. E. C. C o r b r i d g e and E. J . Lowe, J . Chem. S o c , 4555 ( 1 9 5 4 ) . 6 2 . R. J . G i l l e s p i e and C. . Solomons, J . Chem. S o c , 1796 ( 1 9 5 7 ) . 6 3 . . R. C. Thompson, " I n o r g a n i c S u l p h u r C h e m i s t r y " , Ed. G. N i c k l e s s , E l s e v i e r s , Amsterdam, ( I n P r e s s ) . . 6 4 . A. W h i t t l a , Ph. D. T h e s i s , McMaster U n i v e r s i t y , H a m i l t o n (1963) 6 5 . E. G. T a y l o r and C. A. K r a u s , J . Am. Chem. S o c , 6_9, 1731 ( 1 9 4 7 ) . 6 6 . C. R. Witschonke and C. A. K r a u s , J . Am. Chem. S o c , 6 9 , 2472 ( 1 9 4 7 ) . 6 7 . G. Oddo and G. A n e l l i , Gazz. Chim. I t a l . , 4 1 1 , 552 ( 1 9 1 1 ) . 68. A. F i n d l a y , ' P r a c t i c a l P h y s i c a l C h e m i s t r y ' , Longmans, London ( 1 9 5 5 ) . 6 9 . I n t e r n a t i o n a l C r i t i c a l T a b l e s , 5 , H O & 1 3 3 , New Y o r k ( 1 9 2 9 ) . 7 0 . R. P. B e l l , " A c i d s and Bases", Methuen, London ( 1 9 6 1 ) . 7 1 . W. L. J o l l y , I n o r g . Chem., 6 , 1435 ( 1 9 6 7 ) . ' 7 2 . R. J . G i l l e s p i e and R. F. M. W h i t e , Trans. F a r a d . S o c , £ 4 , IS46 ( 1 9 5 8 ) . 7 3 . E. A.Robinson, Can. J . Chem., 40, 1725 ( 1 9 6 2 ) . 

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