Kinetics of the desulphuration of 35S-labelled thiourea in sodium hydroxide studied by chromatographic methods

The kinetics of the desulphuration of 35S-labelled thiourea in aqueous solutions of carbon dioxide-free sodium hydroxide has been studied at 80–100 °C in the range pH 12–13. The undecomposed thiourea and the sulphide ion were separated by paper chromatography and their radioactivity was measured. The desulphuration may be considered to be a second-order reaction SC(NH2)2+ OH–→ NCNH2+ SH–+ H2O. The rate constants are sensitive to the ionic strength of the medium. An activation energy of 18 ± 1 kcal mol–1 was obtained.