Solvent effects on chemical processes. Part 6. The phenomenological model applied to the solubility of naphthalene and 4-nitroaniline in binary aqueous–organic solvent mixtures

Abstract

The phenomenological theory of solvent effects on solubility partitions the free energy of solution into contributions from solvent-solvent interactions (the general medium or solvophobic effect), solvent-solute interactions (the solvation effect), and solute-solute interactions (the intersolute effect). The theory relates the solvent effect on solubility to the mole fractions of the solvent components and the model parameters K, and K2 (which are stepwise solvation exchange constants) and gA (the general medium parameter, where g is a curvature correction factor to the surface tension, and A is the nonpolar surface area of the solute). Solubility data for naphthalene and 4-nitroaniline are given over the entire composition range in aqueous-organic mixtures, the organic cosolvents being methanol, ethanol, propan-2-01, propane-1,2-diol, ethylene glycol, acetone, dimethyl sulfoxide and acetonitrile. The data are quantitatively described by the model. Cosolvents are classified, on the basis of their polarities (as measured by their octan-I -01-water partition coefficient P ) , into a less polar class whose solvation exchange constants increase with log P, and a more hydrophilic class with the opposite tendency. The gA parameter can be reasonably predicted with the empirical relationship gA = -33.4 log P, + 13.4 log P, (A' mol-'), where M and R refer to the organic cosolvent and the solute, respectively. The product g(y, -y,), where y2 and y1 are the surface tensions of pure cosolvent and water, respectively, is close to the dispersion surface energy component of water and many other solvents.

Prediction of Binding Constants of α-Cyclodextrin Complexes

“…The free energy change of any process is considered to receive contributions from solvent-solvent interactions (giving rise to the general medium or solvophobic effect), solvent-solute interactions (the solvation effect), and solute-solute interactions (the intersolute or intrasolute effect). 6,7 One of the processes to which the theory has been applied is complex formation. 8,9 In the fully aqueous solution, our present concern, the free energy change of complex formation is given by eq 1.…”

“…Equation 4 then becomes where [Z] ) Z/2.3kT, and g, which is treated as a constant, has been factored out of ∆gA. The quantity g has been independently estimated, 7,9,10 from solvent effect studies, to have the value 0.42 ( 0.05; inserting this into eq 5 gives eq 6, which is written in this way because ∆A is negative, so -∆A is a positive quantity (having the units Å 2 molecule -1 ).…”

Reaction kinetics and solubility in water-organic binary solutions are governed by similar solvation equilibria

“…Influence of ethanol content in aqueous binary mixtures on the kinetics of (4‐methoxyphenyl)‐2,2‐dichloroacetate (4‐MPDA) hydrolysis (ln k , ○) and on the solubility of naphthalene (ln x 3 , ●) at 25 °C . Ethanol content in the solvent was characterized by its molar fraction XEtOH in the water–ethanol mixtures…”

Solvent Effects on Chemical Processes. 11. Solvent Effects on the Kinetics of Decarboxylative Dechlorination of N-Chloro Amino Acids in Binary Aqueous—Organic Solvents

“…In both these cases the correlation applies to cosolvents having log P equal to -1.0 or higher (more positive); solvents more polar than these (such as DMSO and ethylene glycol) appear to interact by means of an independent mechanism, presumably a hydrophilic interaction. 3,4 These correlations provide some limited empirical capability for prediction of exchange constants. The kinetically measured exchange constants seem to be less sensitive to solvent polarity than are the solubilitymeasured quantities.…”

“…The solvent-to-solvent variation of ∆gA q seen in Tables 3 and 4 has been observed also with solvent effects on solubilities. 3 This variation introduces some ambiguity into interpretations, because the theory assumes that the gA quantities are not composition dependent. Since δ m ∆G rxn q for all systems are related to the reference solvent water, it follows that the gA quantities should have the same value in all solvents if they are to assume the common value in water.…”