Handbook of Solvents - George Wypych - ChemTech - Ventech!

544 Y. Y. Fialkov, V. L. Chumak
Thus Kus is calculated as a slope ratio of
A
coordinates: 1/( Ka - K a ) = (1-xB)/xB and (Ka -
A
K a ) remainder is obtained as Y-intercept.
Dependence of eq. [9.101] is presented in
Figure 9.14.
Kus for proton was calculated in a series
of mixed solvents. It was shown 47 that, when
pyridine, dimethylalanine or diphenylamine
(resolvating agents with decreasing donor
numbers) are added to the solution of
trifluoroacetic acid in DMSO, proton decreases
consecutively and its values are equal
to 2.7x10 4 ; 4.2x10 3 A
Figure 9.14. Dependence of 1/(K and 35.4, respectively.
a - K a ) for CF3COOH
on the mixed solvent composition DMSO (A) - Consideration of permittivity of the
dimethylalanine at different temperatures.
mixed solvent has allowed calculation of proton
in whole concentration range of the
mixed solvent DMSO - diphenylamine. The data have been approximated using equation
[9.55].
ln K us = -12.2 + 3400/T + 453.7/ε - 75043/εT
Equilibrium constants for exchange process of alcohol shell of solvates to water shell
were calculated: 48
+
+
ROH + H O ↔ H O + ROH
[9.102]
2
2 3
The solutions of HCl and HOSO 3CH 3 in aliphatic alcohol (i.e., C nH 2n+1OH) - normal
alcohol C 1-C 5 and isomeric alcohol C 3-C 5 have been studied. If the components taking part
in resolvation process are capable of H-bonding, the anion solvation by these components
cannot be neglected. The differences in K us values for both acids in different solvents may
be explained as follows.
The dependence of K us on permittivity and temperate is described by the equation:
( )
2
ln K = a00 + a01 / T + a02 / T + a10 + a11 / T / ε [9.103]
The coefficients of equation [9.103] are presented in Table 9.5.
Table 9.5. Coefficients of the equation [9.103] for constants of resolvation process
System a00 a01×10 -2
a02×10 -4
a10 a11×10 -3
±δ
HCl - n-alcohol 12.4 46.0 56.3 186.8 71.1 0.3
HCl - isomeric alcohol 13.1 5.9 -36.9 318.4 94.7 0.2
HOSO3CH3 - n-alcohol 6.3 4.4 -5.4 177.7 60.9 0.3
The solvent effect in the following resolvation process was studied: 49