Wilfried Blokzijl

Quantitative analysis of solvent effects on the keto–enol equilibrium of pentane-2,4-dione in aqueous solutions

A quantitative analysis is described for solvent effects on homogeneous chemical equilibria in dilute aqueous solutions in terms of pairwise solute–solute interactions. Solvent effects of a series of monohydric alcohols on the keto–enol tautomeric equilibrium of pentane-2,4-dione (PD) have been measured in order to test the applicability of the new method. Observed medium effects could be successfully accounted for on the basis of contributions of methylene and hydroxy groups. In addition, the dependence of the equilibrium quotient on the concentration of PD has been analysed in terms of cosolvent effects.

Kinetics of hydrolysis in aqueous solution of 1-benzoyl-1,2,4-triazole; the role of pairwise and triplet Gibbs energy interaction parameters in describing the effects of added salts and added alcohols

Kinetic data are reported for the spontaneous hydrolysis of 1-benzoyl-1,2,4-triazole in aqueous solutions at ambient pressure and 298.2 K, in aqueous solutions containing added ethanol, propanol and sodium chloride. Kinetic data are also reported for the same reaction in aqueous mixtures of sodium chloride and ethanol. When either ethanol or propanol are added the rate constant k decreases, plots of ln(k)vs. molality of alcohol being linear. The patterns are accounted for using pairwise Gibbs energy interaction parameters. The rate constant k decreases more dramatically when sodium chloride is added. This pattern is accounted for using pairwise and triplet interaction parameters. The dependence of rate constant on molality of added ethanol in solutions containing fixed molalities of sodium chloride deviates from that predicted using the pairwise interaction parameters indicating a non-additivity of salt and alcohol effects on the rate constant. The deviations increase with increase in molalities of both added salt and added solvent in a direction consistent with a disruption of the substrate-alcohol hydrophobic interactions by added salt.