Theoretical study on peroxyl radical additions to methyl-substituted ethenes

摘要

The electrophilic additions of hydroperoxyl (HO2.) and alkylperoxyl (RO2.) radicals to substituted ethenes were studied using the AM1 semiempirical molecular orbital (MO) methods at the self-consistent field/unrestricted Hartree-Fock (SCF/UHF) level. Reactantlike transition states were predicted for the title additions. The reactivity of an alkylperoxyl radical toward ethenes was found to be decreased as the degree of methyl (Me) substitution on the alkyl group of the radical increased. The relative reactivity and regioselectivity in HO2. additions to substituted ethenes was suggested to be SOMO (singly occupied)-HOMO controlled. A good correlation was established between the activation enthalpy (Delta H-f*) for the studied additions and the Taft polar substituent constants (sigma*) of RO2.. The Evans-Polanyi correlation between Delta H-f(.) and Delta H(r)degrees was justified and the validity of the Hammond postulate was indicated. The calculated results were compared with the available experimental data. (C) 2000 John Wiley & Sons, Inc. [References: 53]