Photoinduced dehydrogenation reaction of CH3NH2 by NO2 in a cryogenic Ar matrix. Identification of the CH2 = NH · H2O complex

The visible light-induced reaction of NO2 with methylamine (CH3NH2) in a cryogenic argon matrix has been investigated using an FTIR spectrometer. The photochemical products were identified as methyleneimine (CH2 = NH), water and nitric oxide. This photoinduced dehydrogenation reaction, CH3NH2 + NO2 + hν → CH2 = NH + H2O + NO, is interpreted by the following reaction sequence: (1) photoexcitation of NO2, (2) oxygen atom transfer from excited NO2 to methylamine and (3) isomerization from the methylamine N-oxide to methylhydroxylamine (intramolecular hydrogen atom migration), followed by (4) dissociation into methyleneimine and water. it was confirmed by the infrared spectrum that two of the dissociation products interact with each other in the matrix cage (CH2 = NH · H2O). This reaction mechanism is also supported by the formation of CD2 = NH · HDO in the CD3NH2/NO2 system.