Thermodynamics of Dissolution of some Dicarboxylic Acids in Water/Ethane-1,2-Diol Mixtures

Abstract

Dicarboxylic Acids / Solvent Effects / Dissociation Constant / Thermodynamics / Relative PermittivityThe pK 1 and pK 2 values of malic, malonic, maleic, succinic, tartaric, and phthalic acids have been determined in ethane-1,2-diol-water media of varying solvent compositions (0-50 wt % ethane-1,2-diol) within the temperature range (25-65 • C). An extrathermodynamic analysis of the obtained results have been examined, in the light of ∆H • -∆S • relationship. The pK values have been correlated with the relative permittivity of the medium according to Born's electrostatic model.

Medium Effects on Dissociation Constants of Maleic and Malonic Acids in Acetone–Water Binary Mixtures. A Thermodynamic Study

“…In this study, the intramolecular hydrogen bonding is greater for maleic acid (Table 3) where K 1 /K 2 ratio for this acid reaches a maximum value of (27 × 10 5 ), where its geometrical structure plays an important role giving chance for such interaction to take place. This value of (K 1 /K 2 ) for maleic acid in acetone-water mixtures is 27 times greater than that reported for the same acid in ethylene glycol-water mixtures under the same experimental conditions [11], indicating greater stabilization of the intramolecular hydrogen bonding in acetone-water mixtures and reflecting the difference in hydrogen bond donating capacity between the two media.…”

“…Its presence as co-organic solvent exerts a pronounced effect on the pK 's of the studied acids. Ethylene glycol and acetone have different relative permittivity (38.66) and (19.56) respectively at 20 • C, the pK values of the studied acids in acetone-water mixtures are higher than those obtained in ethylene glycol-water mixtures of the same weight percent of the organic solvent [11]. In fact this behavior can not only be visualized in terms of electrostatic effects, i.e.…”

“…The effect of these groups on the biological systems has been studied in aqueous and non-aqueous solutions of different solvent mixtures [2][3][4][5] where the dissociation constants and the thermodynamic properties of the systems under study had been determined. The dissociation of weak acids, like carboxylic acids, is affected by solvation of ions, and it attracts a lot of attentions [6][7][8][9][10][11]. Therefore, the present investigation is devoted to the study of the medium effects on the pK a values of two dicarboxylic acids, namely: maleic and malonic acids in aqueous solution containing varying mole fractions of acetone which allows a wide range of relative permittivity.…”

Influence of Solvent upon Rates of Ion Pair Reactions: Studies on the Aquation of Bromopentamminecobalt(Iii) Perchlorate in Binary/Water-Ethan-1,2-Diol Mixtures

“…The values of the malonic acid dissociation constants (K 1 and K 2 ) and the ion pair association constant (K ass ) at different solvent compositions in the temperature range (35 - and DS o ass ) for different experimental conditions are taken from [12,13]. The data given in Table 2 show that the trend of the ion pair rate for malonate is greater than that of succinate [14]; such an increase may be attributed to the increased proportion of malonate dianion compared to succinate dianion (malonic acid has pK a ¼ 2:5 and 5.05) while (succinic acid has pK a ¼ 4:2 and 5.63).…”

Comparison of the leaving groups during the study of the aquation of halopentaammine cobalt(III) complex in tartarate at different percentage of tert-butanol

“…Several achievements were investigated on the kinetics of aquation of halopentaammine cobalt(III) in different media [6][7][8][9][10][11][12]. It is well known that the halopentaammine cobalt(III) complexes aquated by an essentially dissociative process.…”