Structural and solvent effects upon decarboxylation of 2,6-disubstituted benzoyloxyl radicals. A laser flash photolysis study of bis(2,6-disubstituted-benzoyl) peroxides
作者:Jun Wang、Hiroki Itoh、Masahiro Tsuchiya、Katsumi Tokumaru、Hirochika Sakuragi
DOI:10.1016/0040-4020(95)00756-x
日期:1995.10
2,6-dichlorobenzoyloxyl radicals are larger than those of benzoyloxyl, 4-methylbenzoyloxyl and 2-chlorobenzoyloxyl radicals, respectively, in carbon tetrachloride and acetonitrile; however, the values in the former solvent are significantly larger than those in the latter. The rate acceleration with the ortho substituents is ascribed to a nonplanar geometry of the radicals brought about by twisting
在四氯化碳和乙腈中,2,6-二甲基苯甲酰氧基,2,4,6-三甲基苯甲酰氧基和2,6-二氯苯甲酰氧基的脱羧速率常数分别大于苯甲酰氧基,4-甲基苯甲酰氧基和2-氯苯甲酰氧基。但是,前一种溶剂中的值明显大于后者。邻位取代基的速率加速归因于由于取代基的空间效应而使羰基氧基团扭曲而引起的自由基的非平面几何形状。极性溶剂用于稳定自由基的扭曲的电荷转移结构并阻止其脱羧。