EFFECT OF SOLVATING ADDITIVES ON ANION-EXCHANGE EXTRACTION
73
the solvating additive, we can increase the anion-
exchange extraction constant to five orders of magni-
tude by increasing the solvating agent concentration.
TCA
Pic
log K
CONCLUSIONS
(1) Among 27 trifluoroacetophenone derivatives
and related compounds tested as solvating additives in
extraction of trifluoroacetate anions with trinonylocta-
decylammonium picrate in toluene, only those con-
taining the trichloroacetyl group bound to the benzene
ring increase the extraction, provided that the benzene
ring contains unsubstituted H atoms. The introduction
of nitro groups and chlorine atoms into the benzene
ring of the solvating additives increases this effect.
(2) Logarithms of anion-exchange extraction con-
stants of trichloroacetate with trinonyloctadecylammo-
nium picrate in toluene vary in direct proportion with
the solvation constant of trichloroacetate with solvat-
ing additives.
Fig. 2. Correlation between the logarithms of the anion-
exchange extraction constants of TCA anions from the
aqueous phase with TNODA Pic in toluene containing vari-
ous organic additives and sum of the Hammett constants
(3) The apparent anion-exchange extraction con-
stants of trichloroacetate with TNODA Pic in toluene
linearly depend on the sum of the Hammett -con-
stants of the solvating additives.
of substituents in the organic additives. Regression equation
TCA
log K
= 4.10+1.65
.
Pic
REFERENCES
The Hammett equation logK = logK +
con-
0
1. Rakhman’ko, E.M., Physicochemical Principles of
Analytical Application of Extraction with Salts of
Higher Quaternary Ammonium Salts, Doctoral Disser-
tation, Minsk, 1994.
2. Pomelenok, E.V., Influence of Steric Accessibility of
the Exchange Centers of Higher Quaternary Ammoni-
um Salts on the Selectivity of Anion-Exchange Extrac-
tion, Cand. Sci. Dissertation, Minsk, 2004.
tains the parameter
reflecting the sensitivity of
the anion-exchange equilibrium to variation in the tri-
fluoroacethophenone electrophilicity. We found that,
for the extraction systems under consideration,
1.65 0.13. We believe that high value in our sys-
tems is caused by low toluene polarity; it is consistent
with the data on values for anion-exchange equilibria
in chlorobenzene ( = 1.89 0.04) and methyl butyl
ketone ( = 1.71 0.06) reported in [3].
=
3. Karavan, V.S., Nikiforov, V.A., and Ampilogova, N.A.,
Zh. Anal. Khim., 1989, vol. 44, no. 5, pp. 914 916.
The introduction of Cl and NO electron-acceptor
2
4. Gulevich, A.L., Rakhman’ko, E.M., and Podterob, A.P.,
Zh. Fiz. Khim. Rastv., 1996, vol. 70, no. 12, pp. 2192
2193.
groups into the benzene ring of trifluoroacetophenone
sharply increases the anion-exchange extraction of tri-
chloroacetate anions. We believe that this effect is
caused by the fact that the introduced substituents,
exhibiting strong negative inductive effect ( I), in-
crease the electrophilicity of the carbon atoms of the
carbonyl groups in trifluoroacetophenone molecules
and, as a result, enhance their solvating power with
respect to TCA anions.
5. Starobinets, G.L., Rakhman’ko, E.M., and Soroka, Zh.S.,
Zh. Neorg. Khim., 1978, vol. 23, no. 6, p. 1628.
6. Podterob, A.P., Extraction of Substituted Benzoate
Anions with Higher Quaternary Ammonium Salts and
Its Analytical Application, Cand. Sci. Dissertation,
Minsk, 1997.
7. Gulevich, A.L., Anion-Exchange Extraction of Organic
Anions with Higher Quaternary Ammonium Salts and
Its Analytical Application, Doctoral Dissertation,
Minsk, 1997.
We found that substituted trifluoroacetophenones
are strong solvating agents increasing the extraction of
trichloroacetate by three orders of magnitude even at
2
their low content (10 M). Taking into account that
8. Rakhman’ko, E.M., Gulevich, A.L., Podterob, A.P., and
Senin, P.V., Zh. Anal. Khim., 1998, vol. 53, no. 4,
pp. 1 4.
the anion-exchange extraction constant increases in
the direct proportion with increasing concentration of
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 79 No. 1 2006