Kinetic and electron paramagnetic resonance studies of photochemical reactions of gas mixtures of methane, ammonia and water

Abstract

Photoactivation of methane has been kinetically studied in the CH₄–NH₃–H₂O mixture, and the radical intermediates measured by the spin trap (PBN, α-phenyl-N-tert-butylnitrone)–EPR method. The trapped radicals were CH₃O˙(a^N= 1.35, a^H_β= 0.20 mT), ˙CH₂NH₂(a^N= 1.46, a^H_β= 0.26 mT), and ˙CHNH (a^N= 1.48, a^H_β= 0.62 mT). It was suggested that ˙CH₂NH₂ was mainly provided by H abstraction from methylamine and the photolysis of CH₃NH₂ to CH₃NH˙ and ˙CH₂NH₂ was low. The coupling of ˙CH₂NH₂ led to the formation of ethylenediamine, while CH₃NH˙ decayed to CH₂NH from which the ˙CHNH radical was generated by the H elimination. The water photolysis proceeded with a quantum yield of 0.06 in the gas mixture.