THE KINETIC OF OXIDATION OF 4-QARANTHIOL WITH CHLORINE DIOXIDE

Abstract

The kinetics of oxidation of 4-qaranthiol with chlorine dioxide to disulfide in a solution of acetonitrile was studied by electron spin resonance (ESR). This reaction is the initial stage of oxidation of thiol to sulfonic acid. From the EPR spectra of paramagnetic chlorine dioxide in a solution of acetonitrile, the time dependences of its consumption were obtained for various molar ratios of the thiol-oxidant and temperatures (-10, -15, -20 °C). The kinetic and thermodynamic parameters of the first stage of thiol oxidation are determined (reaction rate constants, pre-exponential factor of the Arrhenius equation, activation energy Ea = 79 kJ / mol, enthalpy ΔH = 76.9 ± 2.5 kJ / mol, entropy change ΔS = -1.7 ± 0.9 J / (mol · K)). It is established that the reaction rate is described by a second-order equation for the concentrations of the reagents. The dependence of the conversion of 4-quarantine on the mole ratio of thiol-oxidant is shown by gas-liquid chromatography with mass spectrometric detection. It was found that complete conversion of the starting thiol is achieved with a 1 : 1 reagent ratio. The maximum yield of disulfide is reached at a molar ratio of chlorine dioxide to organic substrate of approximately equal to 0.4 ÷ 0.5.