Attack of trifluoromethyl radicals on ammonia and ammonia-d3

Abstract

Hydrogen abstraction by trifluoromethyl radicals from ammonia and ammonia-d₃ has been studied in the temperature range 113–240°C. The Arrhenius parameters, based on Ayscough's value of 10^13.36 cm³ mole^–1 sec^–1 for the combination of trifluoromethyl radicals, are: [graphic omitted] Comparison of the relative reactivities of methyl and trifluoromethyl radicals in their attack on ammonia and ammonia-d₃ has been made; apparently both polar character and bond energy considerations have to be invoked to account for the observed enhanced reactivity of CF₃ over CH₃ radical attack. The isotope effect for the N—H bond has been measured and is in agreement with zero-point energy differences for the stretching of one N—H bond.