Photo-heterolysis and -homolysis of substituted diphenylmethyl halides, acetates, and phenyl ethers in acetonitrile: characterization of diphenylmethyl cations and radicals generated by 248-nm laser flash photolysis
作者:J. Bartl、S. Steenken、H. Mayr、R. A. McClelland
DOI:10.1021/ja00175a028
日期:1990.9
cations with R = R' = Me to R = H, R' = CF3. The rate constants for reaction of C+ with halides (ion recombination) are -2 X 1O1O M-l s-' (diffusion control). The radicals C' disappear by dimerization and disproportionation, for which a complete mass balance has been achieved by product analysis for the case of the benzhydryl system. At laser-pulse powers > IO mJ electronically excited radicals, C", are
异裂比均裂吸热小得多。均裂和异裂也可以通过与三线态苯乙酮(由 308 nm 光解产生)的反应间接实现。除非被一种或多种 MeO 稳定,否则阳离子主要通过与乙腈反应生成腈离子而衰变。然而,由于该反应是可逆的(如二苯甲基阳离子所示),腈离子对最终(阳离子衍生)产物的形成贡献很小,这是由与痕量水(主要产物,二苯甲基醇)反应产生的。 ; 次要,二苯甲基乙酰胺)。对于 R = R' = Me 到 R = H,R' = CF3 的阳离子,C+ 加到 CH$N 的速率常数在 3.5 X 105 到 3.8 X IO7 sI 的范围内。C+ 与卤化物(离子复合)反应的速率常数为 -2 X 1O1O Ml s-' (扩散控制)。自由基C'通过二聚和歧化消失,对于二苯甲基体系的情况,通过产物分析已经实现了完全的质量平衡。在激光脉冲功率 > 10 mJ 时,通过基态 C' 吸收光量子,在许多情况下另外形成电子激发自由基