Hydrogen and deuterium atom abstraction from trideuteromethyl mercaptan by methyl radicals. Reactivity of methylthio radicals

Abstract

The reaction of methyl radicals with trideuteromethyl mercaptan has been studied in the temperature range 130–200°C in order to determine the rate at which hydrogen and deuterium atom abstraction occurs. Abstraction of the hydrogen atom is facile, the S—H bond being broken about 120 times faster than is the C—D bond. An unusual feature of the reaction is the abstraction of the mercapto group from the substrate by methyl radicals.

Arrhenius parameters (based on a value of 10^13.34 mole^–1 cm³ sec^–1 for the rate of recombination of methyl radicals) have been measured for the reactions:[graphic omitted]

Using the relationships 1n (A₁/A_–1)=ΔS/R and ΔH=E₁–E_–1, Arrhenius parameters have been calculated for the reaction of methylthio radicals with methane. It appears that methylthio radicals do not readily abstract hydrogen atoms from methane and it is suggested that radical-radical reactions are likely to be a more important feature of their chemistry than hydrogen atom abstraction reactions.