Ab initio study on alkyl radical decomposition and alkyl radical addition to olefins

Béla Viskolcz, László Seres

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

The β bond dissociation of alkyl radicals and their reverse reactions, the addition of alkyl radicals to olefins were studied by G3MP2 level of theory to obtain a consistent kinetic data set. Both reaction families can be classified depending on the type of radical formed by β bond scission, namely the CH3, primary, secondary tertiary radical formed. The kinetics of the reaction classes were described by only a limited number of Arrhenius parameters. The unified A factor of 1013.7 s-1 was found for all β bond dissociations. The Arrhenius activation energies are 125, 121, 113 and 103 kJ mol-1, for methyl, primary, secondary, and tertiary radicals, respectively. The activation energies of 32, 25 and 18 kJ mol-1 are calculated for the terminal addition of primary (including methyl), secondary, and tertiary radicals to olefins, respectively. The biologically important nonterminal radical additions to olefins have higher barriers of 37, 31 and 35 kJ mol-1, respectively. At room temperature both strongly exothermic additions can compete with H-atom abstraction. New groups for Benson's group additivity rules were defined to describe activation parameters for the β bond dissociation reactions. The group values were calculated by using the ab initio heats of formation of transition state structures.

Original languageEnglish
Pages (from-to)245-262
Number of pages18
JournalReaction Kinetics and Catalysis Letters
Volume96
Issue number2
DOIs
Publication statusPublished - Apr 1 2009

Keywords

  • Activation energy
  • Activation entropy
  • Thermochemistry
  • β-bond dissociation

ASJC Scopus subject areas

  • Catalysis
  • Physical and Theoretical Chemistry

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