PHOTOINDUCED DEHYDROGENATION REACTION OF CH3NH2 BY NO2 IN A CRYOGENICAR 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 spectrom eter. The photochemical products were identified as methyleneimine (CH 2=NH), water and nitric oxide. This photoinduced dehydrogenation react ion, CH3NH2 + NO2 + hnu --> CH2=NH + H2O + NO, is interpreted by the f ollowing reaction sequence: (1) photoexcitation of NO2, (2) oxygen ato m transfer from excited NO2 to methylamine and (3) isomerization from the methylamine N-oxide to methylhydroxylamine (intramolecular hydroge n atom migration), followed by (4) dissociation into methyleneimine an d water. It was confirmed by the infrared spectrum that two of the dis sociation 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.