Quantum yields in the photolytic oxidation of some sulphur compounds

Abstract

The photolytic oxidation of methyl mercaptan, dimethyl sulphide, and dimethyl disulphide was studied in a batch photolysis apparatus. Short wavelength ultraviolet light was provided by a deuterium discharge lamp and monitored by a monochromator equipped with an extended response photomultiplyer tube. Sulphide concentrations were determined using a gas chromatograph equipped with a flame photometric detector having a sulphur response at 365 nm.The rate of photo-oxidation of methyl mercaptan was found to be a linear function of the photon absorption rate and exhibited a quantum yield of 12. The methyl mercaptan photo-oxidation rate was found to be unaffected by increased oxygen concentration, decreased atmospheric pressure, or the presence of sulphur dioxide.The quantum yield of dimethyl sulphide photo-oxidation was found to be dependent upon air pressure; the quantum yield of 4 at 1 atm pressure increased to 8 at 1/4 atm.The quantum yield of dimethyl disulphide photo-oxidation in air was found to be 1.9 at atmospheric pressure and a disulphide concentration of 7.04 × 10−5M.