Sequential Photoinduced Reaction of Reactant Pairs in Extremely Low Temperature

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Visible light induced oxygen atom transfer from NO_2 to propene has been investigated in low-temperature argon and xenon matrices. The reaction intermediate was propyl nitrite radical and the final products were methyl oxirane and NO.Conformational structure of propyl nitrite radical was determined by the vibrational analysis of N=O and N-O stretching modes for the normal and ^<18>O-isotope-substituted species. From the analysis of absorbance growth behaviors of the infrared bands for propyl nitrite radical and methyl oxirane, first-order rate constants were determined by least squares fittings. The photoreaction of propane and NO_2 in xenon matrices was found to occur more rapidly than in argon matrices. The wavelength dependence of the rate constants is also discussed.The visible light-induced reaction of NO_2 with methlamine in a cryogenic argon matrices has also been investigated using an FTIR spectrometer. The photochemical products were identified as methyleneimine, water and nitric oxide. This photoinduced dehydrogenation reaction is interpreted by the following reaction sequence : (1) photoexcitation of NO_2, (2) oxygen atom tranfer from excited NO_2 to methylamine and (3) isomerization from the methylamine N-oxide to methylhydroxylamine, 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.