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Ionic equilibrium in mixtures of protophobic and protophilic polar non‐hydrogen bond donor solvents: acids, salts, and indicators in acetone containing 5 mol% DMSO
Author(s) -
MchedlovPetrossyan Nikolay O.,
Filatov Dmitriy Yu.,
Goga Sergey T.,
Lebed Alexander V.
Publication year - 2010
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.1616
Subject(s) - chemistry , acid dissociation constant , solvent , dissociation constant , iodide , perchloric acid , dissociation (chemistry) , benzoic acid , inorganic chemistry , picric acid , organic chemistry , aqueous solution , biochemistry , receptor
Properties of a protophobic polar non‐HBD solvent can be strongly modified by introduction of a small amount of a protophilic polar non‐HBD solvent. In this paper, acetone (AC) with 5 mol% additive of DMSO, a solvent with $\varepsilon _{\rm r}^{{\rm 25}} = 22$ , was considered as a media for acid–base reactions. Conductance was used for determination of dissociation constants of a set of salts, hydrogen chloride, and picric acid. The last‐named was also studied by UV‐vis spectroscopy. The introduction of 5 mol% of DMSO results in suppressing, to some extent, the homoconjugation processes in AC media as well as of proton hydration by (possible) traces of water. The dissociation of salicylic acid and 2,4‐dinitrophenol was examined utilizing quinhydrone electrodes in a cell with liquid junction. The p K a values of buffer acids and ${\rm p}a_{{\rm H}^ + }^* $ values of buffer solutions were calculated by taking into account the incomplete dissociation of salts. The response of the glass electrode appeared to be satisfactory, which allowed the estimation of the p K a value of benzoic acid. The apparent ionization constants of 22 acid–base indicators in buffer mixtures and perchloric acid solutions were determined in (AC + 5 mol% DMSO) using the spectrophotometric procedure. Copyright © 2009 John Wiley & Sons, Ltd.