Structural and Solvent Effects upon Decarboxylation of 2,6-Disubstituted Benzoyloxyl Radicals. A Laser Flash Photolysis Study of Bis(2,6-disubstituted-benzoyl) Peroxides

Article abstract of DOI:10.1016/0040-4020(95)00756-X

The rate constants for decarboxylation of 2,6-dimethylbenzoyloxyl, 2,4,6-trimethylbenzoyloxyl and 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 of the carbonyloxyl group due to a steric effect of the substituents.The polar solvent serves to stabilize a twisted charge-transfer structure of the radicals and retards their decarboxylation.