The addition reactions of alkyl and allyl radicals in terminal (t) and non-terminal (n) positions to unsubstituted and methyl-substituted ethenes (propene, 2-methylpropene, 2-methyl-2-butene and 2,3-dimethyl-2-butene) were studied at the semiempirical quantum-chemical level by means of Austin Model 1 (AM1) with half-electron (HE) and unrestricted Hartree-Fock (UHF) approximations. The transition states on the potential energy surfaces were determined with full geometrical optimization by means of the McIver-Komornicki method. The calculated enthalpies of activation (ΔH‡) were found to be greater for the allyl radical additions than for the methyl radical additions in both t and n positions. The ΔH‡ values were greater in the additions of both methyl and allyl radicals to the n position. The Evans-Polanyi correlations between the calculated ΔH° and ΔrH° were justified and the validity of the Hammond postulate was indicated.
ASJC Scopus subject areas
- Condensed Matter Physics
- Physical and Theoretical Chemistry