Application of Laser to Selective Partial Oxidation of Hydrocarbons by Dioxygen

研究了ArF或KrF准分子激光辐照不同引发剂对乙烷、丙烷、环己烷、苯等烃类的部分氧化反应，得到以下结论：(1) N_2O或O_3光解引起石蜡部分氧化反应是由准分子激光对N_2O或O_3进行光化学分解引起的。由N_2O光解产生的单线态氧通过插入碳氢键与碳氢化合物反应生成“热”醇。以O_3为引发剂的反应产物分布表明，与ArF激光和N_2O相比，KrF激光从臭氧中生成O（^1D）对环己醇和环己酮具有更好的选择性。这种优势主要是由于KrF激光不会促进环己酮脱碳为环戊烷和一氧化碳，而ArF激光则会。(2)环己烷在液相中的部分氧化在液相氧化中，对含氧化合物的选择性大于85%，量子产率大于气相反应的10^3倍，这可能是由于环己烷的浓度较高所致。在气相反应中根本没有观察到自由基复合形成的化合物，这可以用液相氧化中的笼效应来解释。(3)准分子激光照射下芳烃的反应在芳烃（苯和甲苯）的光反应中，由于ArF或KrF准分子激光吸收了反应物本身的光解作用，发生了分解成C_2 - C_4烯烃的反应，没有观察到含氧化合物。

Study of partial oxidation of hydrocarbons, such as ethane, propane, cyclohexane and benzene, initiated by irradiation of ArF or KrF excimer laser on various initiators, has led to the conclusions as follows ;(1) Partial oxidation of paraffins initiated by N_2O or O_3 photolysisReaction is initiated by photochemical decomposition of either N_2O or O_3 by excimer laser light. The singlet oxygen produced by the photolysis of N_2O reacted with hydrocarbons by insertion into C-H bond to produce "hot" alcohols. The product distribution of the reaction in which O_3 is introduced as an initiator shows that use of KrF laser light to generate O(^1D) from ozone was found to have the advantage, over ArF laser and N_2O, of better selectivity for cyclohexanol and cyclohexanone. The advantage essentially results from the fact that KrF laser light does not promote the decarbonylation of cyclohexanone to cyclopentane and carbon monoxide, while ArF laser light does.(2) Partial oxidation of cyclohexane in liquid phaseIn the liquid phase oxidation, selectivity for oxygen-containing compounds is over 85%, and quantum yield is more than 10^3 times larger than that in gas phase reaction, which may be due to higher concentration of cyclohexane. The formation of compounds formed by radical recombination, which was not observed in gas phase reaction at all, can be explained by the cage effect in the liquid phase oxidation.(3) Reactions of aromatics by irradiation of excimer laserIn the photoreactions of aromatics (benzene and toluene), decomposition into C_2 - C_4 olefins occurs and no oxygen-containing compounds are observed, due to the photolysis of the reactant itself by absorbing of either ArF or KrF excimer laser light.