Kinetics of the Thermal Decompositions of Diaryl and Dialkyl Disulfides

Abstract

A kinetic study of the thermal decomposition of diphenyl disulfide, its p-methoxy, p-methyl, and p-chloro derivatives, and di-n-butyl and di-t-butyl disulfides in tetralin was made. The rate of decomposition was followed by the decrease of disulfide and the spontaneous first-order rate constants for these disulfides at 196, 207, and 217 °C and the activation parameters were obtained. It was observed that the rates of the decompositions for diaryl disulfides are increased by p-substituents (CH3O>Cl\simeqCH3>H) and that that of di-t-butyl disulfide is comparable to diaryl disulfides, whereas, di-n-butyl disulfide shows no decomposition under these conditions. A reaction scheme of the decomposition including induced decomposition is proposed from the kinetic results and product analysis. Moreover, the properties of a thiyl radical in relation to the above results are discussed from the electronic and ESR spectra of the aryl thiyl radicals generated from the photolysis of corresponding thiols in a glass of 2-methyltetrahydrofuran at −196 °C.