Sequential Photoinduced Reaction of Reactant Pairs in Extremely Low Temperature

本文研究了低温氩、氙介质中NO_2与丙烯的可见光诱导氧原子转移反应。反应中间产物为亚硝酸丙酯自由基，最终产物为甲基环氧乙烷和NO.通过对正态和正态氧同位素取代的亚硝酸丙酯自由基的N=O和N-O伸缩振动分析，确定了亚硝酸丙酯自由基的构象结构<18>.通过对亚硝酸丙酯自由基和甲基环氧乙烷自由基红外吸收光谱的分析，用最小二乘法拟合得到了一级反应速率常数。丙烷和NO_2在氙基质中的光反应比在氩基质中快。用FTIR光谱仪研究了低温氩介质中NO_2与甲胺的可见光诱导反应。光化学产物经鉴定为亚甲基亚胺、水和一氧化氮。该光诱导脱氢反应按如下反应顺序进行：（1）NO_2的光激发，（2）氧原子从NO_2向甲胺的转移，（3）甲胺N-氧化物异构化为甲基羟胺，（4）解离为亚甲基亚胺和水。通过红外光谱证实了两种解离产物在基质笼中相互作用。

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.