A C T A U N I V E R S I T A T I S L O D Z I E N S I S FOLIA CHI MICA 10, 1993
M a ł g o r z a t a Jóźwiak*, Ste fani a T a n i e w s k a - O s i ń s k a * C O M P A R I S O N OF I O N I C E N I H A L P I E S OF T R A N S F E R F R O M
W A I E R TO M I X E D S O L V E N T S W I T H A L C O H O L B Y O S E OF I P f B A N D C s l D I S T R 1 B O TIO N M E I H O D S
The e n t h a l p y of s o l u t i o n of Csl in a m i x ed sol v e n t c o n sis t i n g of n - p r o p a n o l and water was m e a s u r e d at 298.15 K. Based on the m e t h o d of Criss and Cobble, the s t a n d a r d e n thalpy of Csl in the i n v e s t i g a t e d sol vent was c a l cula ted. The s t a n d a r d e n t h a l p y of tra nsfer of e l e c t r o l y t e was d iv ided into ionic c o n t r i b u t i o n s , using the f o l l o w i n g e q u a t i o n A t r H °° (Cs + ) = A trH°°(I ). The r es ults o b t a i n e d were com p a r e d with the values of ionic A ^ H 00 a c q u i r e d at an a s s u m p t i o n that ^■tr^°° (8^ 4) = A ^r H°° (P h ^ P + ), The same a n a l y s i s was ca r r i e d out for aq u e o u s m i x t u r e s c o n t a i n i n g met hano l, e th anol and ter t-bu t a n o l .
I N T R O D U C T I O N
S tu dies on s t a n d a r d e n t halp y of s o l utio n of e l e c t r o l y t e in v ar ious a q u e o u s - o r g a n i c sys tems have been c a r r i e d out for s e v e ral years. S ev eral m e t h o d s for the d i v i s i o n of s t a n d a r d ent h a l p y of tra nsfe r into ionic c o n t r i b u t i o n s have been pro pose d. One of the early m e t h o d s as s u g g e s t e d by L a n g e and M i s c h e n- k o [1] a ss umes that:
A trH ° ° ( C s + ) = A t r H°°(I-) (!) *
D e p a r t m e n t of Phy sica l Che mistry, U n i v e r s i t y of Łódź, P o m o r s k a 18, 91- 418 ł ó d ź , Poland.
This m e t h o d has been c r i t i c i z e d b ec ause of the d i f f e r e n c e in size of Cs + and 1 ’ ions, and c o n s e q u e n t l y A t r Hco( C s + ) t A ^ rH°°(I ). R e c e n t l y the (TATB) m e t hod has been used, a s s u m i n g the i d e n tity of s t a n d a r d e n t h a l p i e s of tra nsfe r of BPh^ and Ph^P + (or P h ^ A s + ) ions from water to a b i c o m p o n e n t s y s tem c o n s i s t i n g of water and o r g a n i c so l v e n t [2]. A l t h o u g h this m e t h o d is very p o pular and c o n v e n i e n t in use, its a s s u m p t i o n s have been more f r e qu e n t l y c r i t ici zed.
In the pr e s e n t study, the r es ults o b t a i n e d by both me t h o d s are c o m p a r e d wit h p l o t t e d val ues of s t a n d a r d e n t h a l p i e s of tra nsfe r of e l e c t r o l y t e from w a t er to mixed a q u e o u s - a l c o h o l i c s o l v e n t s at a t e m p e r a t u r e of 298.15 K.
E X P E R I M E N T A L
C e s i u m iodide, analar g r a de (BDH C h e m i c a l s Ltd. Eng land) was dried at a t e m p e r a t u r e of 333.15 K to c o n s t a n t weight. R e d i s t i l l e d water and n - p ropa nol, ana lar garde, of M e r ck were used for the m e a s u r e m e n t s .
The m e a s u r e m e n t s of heat s o l u t i o n of Csl in m i x t u r e s of n - p r o p a n o l and water were ca r r i e d out at 298.15 K, u s i ng a non- - i s o t h e r m a l - n o n - a d i a b a t i c c a l o r i m e t e r [3]. The e s t i m a t e d e x p e r i me n tal error was 0,5%.
RES ULTS AND D I S C U S S I O N
The v al ues of e n t h a l p y of s o l u t i o n of Csl in water and aqueous n- p r o p a n o l s o l u t i o n s are given in Tab. 1. The m e a s u r e m e n t s were c a r r i e d out in s o l u t i o n s c o n t a i n i n g from 0 to 40 mol% of n - p r o panol in water. When the n - p r o p a n o l c on tent in water e xc eeds 40 mol%, a very poor s o l u b i l i t y of Csl is observed.
Based on the d e t e r m i n e d e n t h a l p i e s of s o l u t i o n of Csl in water and aq u e o u s n - p r o p a n o l sol utio ns, s t a ndar d e n t h a l p i e s of s o l u t i o n were d e t e r m i n e d by the m e t h o d of C r i s s and C o b b l e [4]. The r e s u l t s o b t a i n e d are given in Tab. 2 and i l l u s t rated in Fig. 1. The shape of curve r e p r e s e n t i n g A S H°°= f(mol% of n - p r o p a n o l ) s u g g e s t s that the val ues of s t a n d a r d e n t h a l p y of
T a b l e 1 E n t halp y of s o l u t i o n of Csl in w a t e r - n - p r o p a n o l m i x t u r e s at
298.15 K
m * s H m A s H
mol k g ”1 kJ mol 1 mol k g "1 o e o r—4 1
1 2 3 4 0.00 m a l ?i n - P rOH 5.00 m ol % n - P r O H 0.0023 33.25 0.0042 36.91 0.0045 33.30 0.0045 36.89 0.0052 33.33 0.0 050 36.93 0.0067 33.34 0.0059 36.99 0.0073 33.41 0.0064 37.23 0.0080 33.36 0.0079 37.18 0.0080 37.22 1.50 iron n-P rOH 0.0097 37.17 0.0044 34.82 6.00 m o l 9. n - P rOH 0.0052 34.81 0.0058 34.84 0.0030 36.60 0.0062 34.84 0.0036 36.66 0.0066 35.07 0.0044 36.76 0.0071 35.05 ' 0.0045 36.67 0.0082 34.97 0.0 046 36.66 0.0084 35.09 0.0054 36.70 2.50 mol % n - P r O H 7.50 m ol % n -P rOH 0.0042 35.46 0.0025 36.12 0.0042 35.50 0.0033 36.15 0.0050 35.45 0.0036 36.31 0.0053 35.50 0.0037 36.17 0.0064 35. 64 0.0037 36.22 0.0067 35.65 0.0048 36.13 0.0071 35.82 0.0053 36.31 0.0086 35.75 0.0055 36.33 0.0056 36.36 3.50 m o l 5: n -P rOH 0.0035 36.10 10.00 m ol % n -P rOH 0.0042 36.07 0.0025 34.83 0.0049 36.18 0.0030 34.75 0.0057 36.19 0.0031 34 .80 0.0058 36.30 0.0037 34 .91 0.0059 36.21 0.0041 35.00 0.0061 36.38 0.0060 35.01 0.0066 36.37 0.0071 35.08
T a b l e 1 ( c o n t .)
1 2 3 4
15.00 mol % n -P rOH 40.00 mol% n -P rOH
0 .0 025 32.72 0.0018 20.20 0 .0 039 32.78 0.0022 20.28 0 .0 040 32.81 0.0030 20.25 0.0046 32.90 0.0046 20.22 0.0048 32.86 0.0 050 20. 15 0.0053 32.94 0.0053 20.32 0.0 056 33.00 0.0057 20.24 20.00 mol % n -P rOH 0.0 032 30.37 0.0 034 30. 32 0.0041 30.43 0.0 042 30.35 0.0044 30. 37 0.0051 30.47 T a b l e 2 S t a n d a r d e n t h a l p i e s of sol utio n of Csl in w a t e r - n - p r o p a n o l m i x t u r e s and sta ndard e n t h a l p i e s of tra nsfer of Csl from water to w a t e r - n - p r o p anol m i x t u r e s at 2 9 8 .15 K m ol % n -P rOH 8 JZ in < A trH °° kJ mol 1 kJ m o l - '' 0.0 33.13 0.00 1. 5 34.40 1.27 2.5 35.02 1.89 3.5 35.62 2.49 5.0 36. 54 3.41 6.0 36.40 3.27 7.5 35.88 2.75 10.0 34. 52 1.39 15.0 32. 31 -0.82 20.0 29.95 -3.18 40.0 20. 24 -12.89
Fig. 1 . S t a n d a r d e n t h a l p y of s o l u t i o n of Csl in n - P r O H - w a t e r m i x t u r e s at 298.15 K
s o l u t i o n of Csl i n c r e a s e s with inc r e a s i n g n - p r o p a n o l c o n t e n t in water and r ea ches m a x i m u m w it hin the range 5-6 mol% of n-PrOH. The p o s i t i o n of this m a x i m u m is s im ilar to that of e ar lier c ur ves il l u s t r a t i n g A ^ H 00 for Nal [5], NaCl [6], NaB Ph^ [7] and Ph^PCl [7] in the mixed so l v e n t c o n t a i n i n g water and n-PrOH. M ax ima of As H c o of e l e c t r o l y t e s vs. the mixed s ol vent c o m p o s i t i o n within
Fig. 2 a. S t a n d a r d e n t h a l p i e s tra n s f e r of the e l e c t r o l y t e s from water to M e O H - w a t e r m i x t u r e s at 2 9 8 .15 K: o - Ph.PBPh, ; x - NaCl;
A - NaBr j a - N a I ; o - KI; ■ - Csl 4
b. Ionic e n t h a l p i e s of tra n s f e r from w a t er to MeOH-water m i x t u r e s b a s ed on the c o n v e n t i o n A t H 00 ( C s + ) = A ^ H ® (I") at 298 .15 K: ■ - C s + = I~; x - N a + ; □ - K + ; • - P h ^ P + ; * Cl~; A Br"; o
-- BPh^
c. Ionic e n t h a l p i e s of tra nsfe r from water to MeOH-water m i x t u r e s based on the c o n v e n t i o n A t r H°°(PPh^) = A trH°°(BPh‘ ) at 298 .15 K: • - P h 4P + = B P h ^ X - Na + ; □ - K + ; ■ - C s + ; * - Cl"; A - Br” ; a - I"
the range of hig h w a t er co n t e n t have been also o b s e r v e d in other w a t e r - a l c o h o l sy s t e m s [8-14].
The o b t a i n e d val ues of s t a n d a r d e n t h a l p y of s o l u t i o n of Csl in the w a t e r - n - p r o p a n o l s y s t e m were used to c a l c u l a t e ionic e n t h a l p i e s of tra n s f e r from water to the mixed s o l v e n t a c c o r d i n g to the f o l l o w i n g e q u a t i o n (1).
In order to c a l c u l a t e the s t a n d a r d ent h a l p y of tra n s f e r of N a + from water to the w a t e r - n - P r O H system, the v a l u e s of A H“
Q (Nal) were taken from the p ap er of P i e k a r s k i [5] , while the data c o n c e r n i n g Ph^ PCl and NaB Ph^ were taken from our p r e v i o u s study [7j and those for NaCl - from the paper of N o w i c k a et al. [6], (Fig. 4a). The c a l c u l a t e d v al ues of s t a n d a r d e n t h a l p y of tra n s f e r of ions from w at er to the w a t e r - n - P r O H m i x t u r e are gi v en in Tab. 5 and i l l u s t r a t e d in Fig. 4b. The same table c o n tains ionic v al ues of A ^ H 00 c a l c u l a t e d by the TATB (TPTB) m e t h o d (Fig. 4c) for the p u r p o s e of c o m p a r i s o n .
The a n a l y s i s of the p l o t e d re s u l t s o b t a i n e d i n c l u d e d also data c o n c e r n i n g A ^ H 00 of e l e c t r o l y t e s , A t r H“ of ions, o b t a i n e d by the Csl m e t h o d and A ^ H 00 of ions, o b t a i n e d by the TATB method, w hi ch refer also to a q u e o u s m i x e d s o l v e n t s c o n t a i n i n g MeOH (Tab. 3, Fig. 2) [8], EtOH (Tab. 4, Fig. 3) [9, 10] and t e r t - B u O H (Tab. 6 , Fig. 5) [ll, 12, 14J . Plots "a" show A ^ H 00 of e l e c t r o l y tes, p l o ts "b" - A t r H°° of ions, o b t a i n e d by the m e t h o d of L a n- g e and M i s c h e n k o [l], and plots "c" i l l u s t r a t e A t r H°° of ions, o b t a i n e d by the TATB (TPTB) method. All the e n th a l p i e s data are p l o t e d vs. the c o m p o s i t i o n of w a t e r - a l c o h o l s o l v e n t .
As is seen in all the "a" plots c o n c e r n i n g A ^ H 00 of e l e c tro lytes, m a x i m a of this f u n c t i o n are o b s e r v e d w i t h i n the reg ion of high w at er c o n t e n t in all the m i x t u r e s involved.
Plots "b", i l l u s t r a t i n g A ^ H 00 of ions from w a t e r to the w a t e r - a l c o h o l sol vent, show also m a x i m a of A ^ H 00. The s h a pe of these c u r v e s w i t h i n the w h o l e r an ge of c o m p o s i t i o n is s i m i l a r to that s h o w n in p l o ts "a", w h i c h to be pro bable.
On the other hand, plots "c" p r e s e n t d i f f e r e n t s h a pe of the c u r v e s i l l u s t r a t i n g A ^ H 03 of ions from w a t er to w a t e r - a l c o h o l m i x e d so l v e n t (the v a l ues o b t a i n e d by the TPTB or TATB method). W i t h i n the r a n ge of h ig h w a t er con tent, e xt rema of this f u n c t i o n
T a b l e 3 Ionic e n t h a l p i e s of transfer from water to w a t e r - m e t h a n o l m i x t u
res at 298.15 K mol% MeOH *trH°° kJ mol -1 a b a b a b a b Na + Na + K + K + Cs + Cs + P h 4 P + P h 4 P + 5.88 1.23 -0.96 0.98 - 1.21 1.07 -1.13 16.50 14.31 12.33 2.05 2.09 1.34 1.30 1.13 1.17 24.23 24.27 19.44 1.99 4.85 0.86 3.72 0.31 3.18 24.95 27.82 27.27 1.26 5.86 0.33 4.94 0.63 3.97 21.01 25.61 36.02 -0.06 5.06 -0.44 4.69 -1.74 3.39 18.03 20.88 45. 76 -1.15 3.77 -1.74 3 . IB -2.91 2.01 10.65 15.56 56.78 -3.85 0.84 -3.85 0.84 -4.31 0.38 6.53 11.21 69.26 -6.26 -2.30 -6.26 -2.30 -5.54 -1.59 3.62 7.61 83.52 -10.29 -10.84 -9.37 -9.92 -7.11 -7.66 2.55 2.01 100.00 -14.73 -20.59 -13.05 -18.91 -7.87 -13.72 4.23 -1.76 Cl" Cl" Br" Br' I" I' B P \ b p*; 5.88 0.65 2.85 0.90 3.1 1.07 3.26 12.08 14.31 12.33 1.13 1.09 1.09 1.05 1.13 1.09 24.35 24.27 19.44 1.49 -1.38 0.94 -1.92 0.31 -2.55 30.69 27.82 27.27 1.88 -2.72 0.63 -3.97 0.63 -5.23 30.25 25.61 36.02 0.21 -2.64 0.27 -4.85 -1.74 -6.86 26.00 20.88 45.76 2.49 -2.43 0.10 -4.81 -2.91 -7.82 20.44 15.56 56. 78 2.59 -2.09 0.25 -4.44 -4.31 -9.00 15.90 11.21 69.26 3.49 -0.46 0.44 -3.51 -5.54 -9. 50 11.57 7.61 83. 52 3.81 4. 35 0.50 1.05 -7.11 -6.57 1.46 2.01 100.00 2.55 8.41 -1.26 4.60 -7.87 - 2.01 -7.07 -1.76
a - ionic e n t h a l p i e s of tra nsfe r from water to m i x ed s ol vent ba s ed on the c o n v e n t i o n A ^ H 00 (Cs + ) = A ^ H 00 (I ).
b - ionic e n t h a l p i e s of tra nsfe r from water to m i x e d s ol vent based on the c o n v e n t i o n A ^ H 00 (BPh^) = A ^ H 00 ( P h ^ P * ) .
60 fiO moi % EtOH
Fig. 3 a. S t a n d a r d e n t h a l p i e s of tra nsfe r of the e l e c t r o l y t e s from w a t er to E t O H - w a t e r m i x t u r e s at 298.15 K: o - P h ^ P B P h ^ ; a
-- Nal; □ -- K I ; • -- CsCl; § -- CsBr
b. Ionic e n t h a l p i e s of tra nsfer from water to EtOH-water m i x t u r e s b a s e d on the c o n v e n t i o n A ^ H 00 ( C s + ) = A ^ H 00 (I") at 2 98 .15 K: ■ - C s + = I ; x - N a + ; o - K + ; • - P h ^ P + ; * - Cl ; A - Br ; o - BPh^ c. Ionic e n t h a l p i e s of tra nsfe r from water to E tOH-water m i x t u r e s b ased on the c o n v e n t i o n A. H00 (PPht) = A. H00 (B P h A ) at 2 98 .15 K:
tr Na +
tr - C s H
a)
A H * [ k J mol"1! Fig. 4 a. S t a n d a r d e n t h a lpie s of t r a n s f e r of the e l e c t r o l y t e s from w ater to n - P r O H - w a t e r at 298.15 K: o - Ph4PBPh4 ; x - NaCl; A - Nal; ■ - Csl b. Ionic e n t h a l p i e s of t r a nsfe r from w a t er to n - P r Q H - w a t e r mixtures ba sed on the c o n v e n t i o n A trHco( C s + ) = A t r H“ ( D at 298.15 K: ■ - Cs+ = I"; x N a + ; • P h 4P + ; * -- C l -- ; o -- B P h 4 c. Ionic e n t h a l p i e s of t ra n s f e r from water to n - P r O H - w a t e r m i x t u r e s based on the c o n v e n t i o n A t r H“ (PPh;) = A trH°°(BPh;) at 298 .15 K: • - P h 4P + = = B P h 4 ; x - N a + ; ■ - Cs + * - Cl"; A - I" _J______ I--- 1--- --- m-20 AO mol % n-PrOHFig. 5 a. S t a n d a r d e n t h a l p ies of t r a nsfe r of the e l e c t r o l y t e s from w a t er to t - B u O H - w a t e r m i x t u r e s at 298 .15 K: o P h ^ s B P h ^ ; x N a C l ; ® KBr j o K I ; a -- CsCl b. Ionic e n t h a l p i e s of t r a n sfer from water to t-B uOH- -wa ter m i x t u r e s b a s ed on the c o n v e n t i o n A t r H°°(Cs+ ) = = A trH °° (I") at 2 98 .15 K: ■ - C s + = I ~ ; x - N a + ; □ - K+; • - Ph^As+ ; * - Cl- ; o - BPh^ c. Ionic e n t h a l p i e s of tran sfer from water to t-BuOH- -wa ter m i x t u r e s b a s ed on the convention A.trHatPh^As+) = = A trH°° (BPh^) at 298.15 K: • - P h ^ A s + = BPh^; x - N a + ; □ - K + ;■ - C s + ; * - Cl";
T a b l e 4 Ionic e n t h a l p i e s of tra n s f e r from water to w a t e r - e t h a n o l m i x t u
res at 298.15 K mol% i t I H -kJ mol~* EtOH a b a b a b a b Na + Na + K + K + Cs + Cs + P h 4P + P h 4 P + 2.02 0.95 0.73 0.86 0.65 0.68 0.43 9.52 9.27 6.77 3.02 3.79 2.60 3.38 2.06 2.81 26.46 27.21 10.99 3.75 6.63 2.89 5.75 2.00 4.91 35.46 30.37 14.94 3.75 8.63 2.72 7.60 1.30 6.19 27.40 32.37 25.44 2.65 4.70 0.90 2.95 - 1.22 0.04 19.74 21.00 42.07 0.57 -0.27 -1.61 -2.48 -4.36 -5.11 13.52 12.77 55.30 -1.09 -2.32 -3.19 -4.50 -5.94 -7.09 11.47 10.32 64.00 -1.90 -3.43 -3.81 -6.30 -6.42 -7.92 10.13 8.63 71.70 -2.81 -4.02 -3.14 -5.47 -6 . 56 -7.67 0.43 7.32 76.40 -3.45 -4.46 -4.46 -5.46 -6.56 -7.57 7.07 6.86 Cl" Cl" Br" Br" I" I" BPh; Bp*; 2.02 0.24 0.49 0.48 0.73 0.68 0.90 9.05 9.27 6.77 1.40 0.64 1.54 0.79 2.06 1.29 27.90 27.21 10.99 2.48 -0.42 2.04 -0.87 2.00 - 0.00 41.25 38. 37 14.94 3.33 -1. 56 2.22 -2.67 1.30 -3.50 37.25 32.37 25.44 3.79 1. 74 1.76 -0.30 - 1.22 -3.27 23.05 21.80 42.07 2.89 3.60 - 0.02 0.73 -4.36 -3. 52 11.93 12.77 55.30 1.95 3. 23 -1.47 -0.32 -5.94 -4.71 9.09 10.32 64.00 1.89 3.46 -1.63 -0.13 -6.42 -4.09 7.10 8.63 71.70 1.88 3.70 -1.73 -0.62 -6.56 -5.35 6.11 7.32 76.40 2.22 3. 23 -1.67 -0.66 -6.56 -5.55 5.05 6.86
a - ionic e n t h a l p i e s of tra nsfe r from water to m i x e d sol vent b a s ed on the c o n v e n t i o n A ^ H 00 (Cs + ) = A ^ H ° ° ( I ” ).
b - ionic e n t h a l p i e s of tra nsfe r from w a t er to m i x e d s ol vent b a s ed on the c o n v e n t i o n A ^ H 00 (BPh~) = A trH°° (P h ^ P '*’).
T a b l e 5 Ionic e n t h a l p i e s of tra nsfe r from water to w a t e r - n - p r o p a n o l m i x
tures at 293.15 K mol% n -P rOH A t r H “ kJ m o l ”1 a b a b a b Na + Na + Cs + Cs + Ph. P + 4 P h 4 P + 1.5 0.71 0.08 0.63 0.00 10. 33 9.71 2.5 1.24 -0.92 0.94 - 1.21 20.45 19.08 3.5 1. 77 -0.42 1.24 -0.96 31.31 29.16 5.0 2.57 6.99 1.70 6.11 36.00 40.46 6.0 3.52 8.99 1.63 7.11 37.62 43.09 7.5 3.72 6 . 78 1.38 4.44 33.30 36.40 10.0 2.91 0.50 0.69 -1.72 29.60 27.24 20.0 0.08 -5.89 -1.59 -7.57 22.76 16.82 40.0 -2. 74 -9.20 -6.05 -13.31 20. 36 13.89 Cl" Cl' I" r BPh; 1.5 0.34 0.96 0.63 1.26 9.08 9.71 2.5 0.60 2.76 0.94 3.09 16.92 19.08 3.5 0.95 3.10 1.24 3.43 26.97 29.16 5.0 1.53 -2.93 1.70 -2.12 44.88 40.46 6.0 1.46 -4.02 1.63 -3.84 48.57 43.09 7.5 2.47 -0.59 1.38 -1.67 39.46 36.40 10.0 2.49 4.89 0.69 3.09 24.83 27.24 20.0 3.89 9.87 -1.59 4.39 10.84 16.82 40.0 0.23 6.69 -6.05 0.42 7.43 13.89
a - ionic e n t h a l p i e s of tra nsfer from water to m i x ed s ol vent ba s ed on the c o n v e n t i o n A ^ H 00 (Cs + ) = A t H°°(I~).
b - ionic e n t h a l p i e s of tra nsfe r from water to m i x e d so l v e n t based on the c o n v e n t i o n A tr.H°° (BPh~) = A ^ H 00 ( P h 4P + ) .
T a b l e 6 Ionic e n t h a l p i e s of t r a nsfe r from water to w a t e r - t e r t - b u t a n o l
m i x t u r e s at 290.15 K 8 JZ M +■> < mol% kJ m o l -1 t-BuOH a b a b a b a b Na + Na + K + K + Cs + Cs + P h ^ A s + P h 4A s + 1.26 0.91 -0.49 0.83 -0.57 0.94 -0.46 12.38 10.98 2.63 2.07 -0.18 1.85 -0.40 1.74 -0.51 27.18 24.93 4.11 3.30 11.96 3.05 11.72 2.51 11.18 39.47 48.14 5.73 4.67 18.68 3.81 17.83 2.70 16.72 35.23 49.25 7.49 4.58 12.94 3.50 11.86 2.26 10.62 27.81 36.18 9.43 4.16 8.53 3.07 7.45 1.58 5.96 22.71 27.09 11.57 3.71 5.42 2.41 4.12 0.88 2.59 20.70 22.41 13.94 3.10 3.31 1.76 1.99 0.12 0.34 19.46 19.68 Cl" Cl" Br" Br" r I" BPh^ BPh; 1.26 0.44 1.84 0.37 1.77 0.94 2.34 9.58 10.98 2.63 0.97 3.22 0.97 3.22 1.74 3.99 22.68 24.93 4.11 2.11 -6.56 1.72 -6.95 2.51 -6.16 56.80 48.14 5.73 3.91 - 10.11 2.84 -11 .18 2.70 -11.32 63.26 49.25 7.49 5.19 -3.17 3.72 -4.64 2.26 -6.10 44.54 36.18 9.43 5.65 1.27 3.71 -0.67 1.58 -2.80 31.46 27.09 11.57 5.80 4.09 3.70 1.99 0 .8B -0.83 24.12 22.41 13.94 5.87 5.65 3.34 3.11 0.12 -0.11 19.89 19.68
a - ionic e n t h a l p i e s of tra nsfe r from water to m i x e d s ol vent based on the c o n v e n t i o n A ^ H 00 (Cs + ) = A t r H°°(I ).
b - ionic e n t h a l p i e s of t r a nsfe r from w at er to m i x e d sol v e n t ba s ed on the c o n v e n t i o n A ^ H 00 (BPh^) = A 00 (Ph^As + ).
for ca t i o n s and a n i o n s being a lm ost like m i r r o r r e f e l e x i o n s , are obs erve d, w h i ch s e e ms to be r a t her strange. It is s e e ms worth m e n t i o n i n g the a s s u m p t i o n s of the TATB (TPTB) method:
1 - BPh^ and Ph^P* or Ph^ As* are the same size and have the same c o n t r i b u t i o n to the transfer ent halpy;
2 - c h a r g e s of both ions are the same and fully she athed; 3 - the ions react with the sol v e n t in the same way and rat her weakly.
Both ions (BPh^ and Ph^P + or Ph^ As*) have four phe nyl g ro ups each and hence they are lik ely to un d e r g o h y d r o p h o b i c h y d r a t i o n w i t h i n the w a t e r - r i c h region. It has been o b s e r v e d in our p r e v i o u s st u d i e s that the m a x i m a of A ^ H 00 of these s a l ts c o n t ai ning them are very high [15], w h i ch is a s s o c i a t e d with the h y d r o p h o b i c h y d r a t i o n of these ions. The h e i g h t s of these m ax ima are the h i g her the gr e a t e r is the h y d r o p h o b i c i t y of o rg anic sol v e n t [ 16]. If the e f f e c t s of h y d r o p h o b i c h y d r a t i o n of both ions and other i n t e r a c t i o n s were the same, this w o u ld not affect the ionic A ^ H 00 since the initial a s s u m p t i o n s are fulfilled.
M a r c u s has shown in his paper [17] that the i n t e r a c tions of PPh^ and BPh^ wit h water are not the same. U n l i k e the b e h a v i o u r of water in the p r o x i m i t y of BPh^, in the case of PPh^ w ater e nt ers b e t w e e n the phenyl g r o ups of this ion. H e n ce the i n t e r a c t i o n s b e t w e e n these ions and water or w a t e r - o r g a n i c s o l v e n t s are not the same, which p r o b a b l y b r i ngs about d i f f e r e n ces in the h ei ght of m a x i m u m A ^ H 00. P r o b a b l y it leads to the m i r r o r r e f l e x i o n s of A ^ H 00 ( i n o r gan ic ions) m e n t i o n e d earlier. T h e r e f o r e the d i v i s i o n of A ^ H 00 (Ph ^PBP h^ or P h ^ A s B P h ^ ) into equal c o n t r i b u t i o n s for BPh^ and P h ^ P + or P h ^ A s * is not jusfied.
It can be seen (pl ots "c") that the h e i g h t of e x t r e m a of A t r H °° (°r 9anic i ° n s) are the hig her the gr e a t e r is the h y d r o p h o b i c i t y of solvent. In addition, in the case of an alcohol w it h larger m o l e c u l e s such as those of n - P r O H and ter t-Bu OH, d o u b l e e xt rema are o b s e r v e d w i t h i n the w a t e r - r i c h region, which is d i f f i c u l t to exp lain. It has been shown p r e v i o u s l y that the p r e s e n c e of ext r e m a s im ilar to m i r r o r r e f l e c t i o n s is br o u g h t about by water p r e s e n t in the m i x ed so l v e n t [18}.
W it hin the r eg ion above 50 mol% of o r g a n i c so l v e n t the s h a pes of c ur ves i l l u s t r a t i n g A ^ H 00 o b t a i n e d by the Csl and TATB (TPTB) m e t h o d s are similar. This is the reg ion w h e re the b e h a v i o u r of PPh^, BPh^, C s + and I" is not d i f f e r e n c i a t e d by the h y d r o p h o b i c hyd rati on.
It is c o n c e i v a b l e that the TATB (TPTB) m e t h o d may be used for the d i v i s i o n of û t r H°° *nto i o n ic c o n t r i b u t i o n s in non aq u e o u s solvents. The p r e s e n c e of water may lead to e r r o r e o u s c o n c l u s i o n s about i n t e r a c t i o n s in s o l u t i o n s of b e c a u s e the h y d r o p h o b i c h y d r a t i o n of or g a n i c ions used for the salts e n t h a l p i e s d i v i s i o n and of o r g a n i c cos olve nts.
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R
IT
[15] S. T a n i e w s k a-0 s i ń s k a, M. J ó ź w i a k , J. Chem. Soc. Far a d a y Trans., 1, 84.. 2077 (1988).
[16] S. T a n i e w s k a-0 s i ń s k a , M. J ó ź w i a k , L. K a-m i ó s k a-B a r t e 1 , Thera-mochia-m. Acta, 200. 99 (1992). [17] Y. M a r c u s, Pure & Appl. Chem. , 2§.> 1721 ( 1986).
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M a ł g o r z a t a Jóźwiak, S t e fani a Taniewska-Osiriska
PO R Ó W N A N I E J O N O W Y C H ENT ALPI I P R Z E N I E S I E N I A Z WODY DO M I E S Z A N Y C H R O Z P U S Z C Z A L N I K Ó W Z A L K O H O L A M I O T R Z Y M A N Y C H PRZEZ W Y K O R Z Y S T A N I E
DWÓCH M E T O D PODZIAŁU: TPTB (TATB) ORAZ Csl
Z m i e r z o n o e n t a l p i ę r o z p u s z c z a n i a Csl w mie szanym r o z p u s z c z a l niku n - p r o p a n o l - w o d a w t e m p e r a t u r z e 2 98 .15 K. S t a n d a r d o w ą e n t a l pię r o z p u s z c z a n i a Csl w tych r o z p u s z c z a l n i k a c h o b l i c z o n o m e t odą C r i s s a i C o b b l e ’a. S t a n d a r d o w a e n t a l p i a p r z e n i e s i e n i a e l e k t r o l i tów była p o d z i e l o n a na ud z i a ł y jonowe, przy w y k o r z y s t a n i u r ó w n a nia
A t r H " (Cs + ) = A t r H°° (I")
O t r z y m a n e w a r t o ś c i jon owe A ^ H 00 p o r ó w n a n o z a n a l o g i c z n y m i , uz y s k a n y m i przy z a s t o s o w a n i u m e t o d y TATB
A t r H°° (B P h ^ ) = A t r H°° ( P h 4 P + )
Taką samą an a l i z ę p r z e p r o w a d z o n o dla u k ł a d ó w wody z m e t a n o lem, e t a n o l e m i t e r t - b u t a n o l e m .
