Influence of organic solvents on rate of oxidization of sulfoxide by peroxy acids

Abstract

The rate of the oxidation reaction of sulfoxides with peroxy acid in various organic solvents was studied. In this work we used dimethyl sulfoxide, dibutyl sulfoxide and diphenyl sulfoxide as substrate and peroxydecanoic, peroxybenzoic, peroxydodecanoic, and peroxypentanoic acids were taken as oxidant. The reaction mechanism involving the rapid formation of the sulfoxide-peroxyacid intermediate, which is decomposed during the second stage to form carboxylic acid and corresponding sulfone. The second stage is the rate-limiting step. It has been found the effective rate constants (k) and activation energy (E act ) for the studied process. Between the parameters of the transition state, ΔН ≠ and ΔЅ ≠ is a linear relationship indicating the presence of the compensative effect in all series of experiments. The reaction medium affects the rate of oxidation. Correlation equations between the rate constants of the reactions and the physicochemical parameters of the solvents were proposed. The correlation equation for effective rate constants and the basic physicochemical parameters of solvents at 318 K has the form: k = 17.1292 + (1027.5613 ±216.2400 )f(n) + (45.5329 ± 51.1522)f (ε) + + (0.1208 ± 0.0761)B – (3.2629 ± 1.2885)E T – (0.2047 ± 0.0913)δ 2 – (0.0605 ± 0.4335)V м , N =12; R=0,9800; S= 8.7942; F= 0.5715 The polarizability, basicity, electrophilicity and Hilderbrand's function of solvent affects the oxidation process. The influence of polarization and molar volume on the rate of oxidation of the sulfoxide decay process is negligible. Correlation equations for effective rate constants for other temperatures are similar. The proposed correlation equations relate the parameters of the transition state of the oxidation process and the physic-chemical parameters of solvents. Keywords: sulfoxides, peroxy acids, the influence of solvents, correlation equations.