AM1 studies on alkyl and allyl radical additions to methyl-substituted ethenes and on the β-bond scissions of the radicals formed

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Abstract

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.

Original languageEnglish
Pages (from-to)135-146
Number of pages12
JournalJournal of Molecular Structure: THEOCHEM
Volume277
Issue numberC
DOIs
Publication statusPublished - Dec 10 1992

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Hartree approximation
Potential energy surfaces
Addition reactions
Butenes
cleavage
Enthalpy
Chemical activation
Electrons
butenes
Propylene
axioms
enthalpy
potential energy
activation
optimization
ethylene
methyl radical
2,3-dimethyl-2-butene
austin
propylene

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Computational Theory and Mathematics
  • Atomic and Molecular Physics, and Optics

Cite this

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title = "AM1 studies on alkyl and allyl radical additions to methyl-substituted ethenes and on the β-bond scissions of the radicals formed",
abstract = "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.",
author = "T. K{\"o}rtv{\'e}lyesi",
year = "1992",
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TY - JOUR

T1 - AM1 studies on alkyl and allyl radical additions to methyl-substituted ethenes and on the β-bond scissions of the radicals formed

AU - Körtvélyesi, T.

PY - 1992/12/10

Y1 - 1992/12/10

N2 - 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.

AB - 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.

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U2 - 10.1016/0166-1280(92)87136-N

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