A flash photolytic study of thiatriazoles and mesoionic oxathiazoles. The thermal decomposition of nitrite sulphides

Abstract

Benzonitrile sulphides have been generated by irradiation of 4-phenyl-1,3,2-oxathiazolylium-5-olate and of 5-aryl-1,2,3,4-thiatriazoles. Rate constants for the first-order decay of the nitrile sulphides were measured in 96% ethanol at 10–30 °C and the results used to calculate activation parameters, E_a 18.88 and 17.20 kJ mol^–1 and ΔS–121.8 and –132.7 J mol^–1 K^–1 for 4-BrC₆H₄CNS and 4-MeC₆H₄CNS, respectively. The decay reaction is 3–4 times slower in CCl₄. A Hammett ρ-value of 2.2 was calculated. Thermochemical relations between HCNS hnd the decomposition products, HCN and S, have been obtained by ab initio calculations. The mechanism of sulphur extrusion is discussed.