Hydrogen-abstraction reactions by ethyl radicals from methylamines and hydrazine

Abstract

By photolysis of diethyl ketone in the presence of the amine or hydrazine Arrhenius parameters have been obtained for hydrogen-abstraction reactions of the ethyl radicals: [graphic omited] These results are based on an assumed rate constant for the combination of ethyl radicals given by log k₁= 14·0 (mole^–1 cm.³ sec.^–1). For the reactions with methylamine and dimethylamine the Arrhenius parameters are derived from composite rate constants for the radical attack at both methyl and amino-groups.

The activation energy for attack of ethyl radicals on hydrazine is similar to that for attack of methyl radicals on hydrazine despite the additional 6 kcal. exothermicity of the latter reaction. It appears that alkyl radicals have the same reactivity in hydrogen-abstractions when the substrate contains a relatively weak X–H bond. The results for reactions of ethyl radicals with methylamines are compared with the analogous reactions involving methyl radicals.