Abstract: | The electrophilic additions of hydroperoxyl (HO ), alkylperoxyl (RO ), and halogenated alkylperoxyl radicals to ethylene were studied using the AM1 and PM3 semiempirical MO methods at the SCF/UHF level. Reactantlike transition states were predicted for the title additions. The AM1 activation enthalpies (ΔH ) were found to be increased in the order HO <CH3O <C2H5O <i‐C3H7O . The reactivity of an alkylperoxyl radical toward ethylene was found to be increased as the degree of halogen substitution on the alkyl group increased. A good correlation was established between ΔH and the Taft polar substituent constants, σ*. The Evans–Polanyi correlation between ΔH and ΔH was justified and the validity of the Hammond postulate was indicated. The calculated results were compared with the available experimental findings. ©1999 John Wiley & Sons, Inc. Int J Quant Chem 71: 273–283, 1999 |