Isomerization of thiourea to ammonium thiocyanate and isotopic exchange between [35S]thiourea and diphenyl tetrasulphide

Abstract

The specific rate of isomerization of thiourea to ammonium thiocyanate has been determined at 120° in 1 : 1 ethanol–xylene and in ethanol–benzene by radiochromatography using ³⁵S-labelled thiourea. The isotopic exchange between [³⁵S]thiourea and diphenyl tetrasulphide in 1 : 1 ethanol–xylene, studied by radiochromatography, shows that the tetrasulphide exchanges only one sulphur atom with thiourea at 100° and two sulphur atoms at 120°. The rate constant for exchange [k₂ 9·57·10^–7 l (g-atom)^–1 s^–1] could only be determined at 100° because at 120° the rate of isomerization of thiourea was too high.