High accuracy ab initio calculations on reactions of OH with 1-alkenes. The case of propene

Róbert Izsák, Milán Szori, Peter J. Knowles, B. Viskolcz

Research output: Contribution to journalArticle

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Abstract

The energetics of terminal, central OH-additions as well as allylic H-abstractions by OH in its reaction with propene was studied as proxies for the 1-alkenes + OH reactions using several single and multireference ab initio techniques with basis set extrapolation where possible. Selection of the localized occupied orbitals forming the active space for multireference methods is discussed. Initial geometries of the reactants, prereaction complex (π-complex), and transition states were determined at the [5,5]-CASPT2/cc-pVTZ level of theory. Frequency analysis was also carried out at this level with the introduction of a scale factor. Analyzing the results, it will be concluded that multireference effects are negligible, and from the various single reference models we will opt for UCCSD(T)/cc-pVTZ for final geometry optimizations and vibrational frequency analysis. These results will be compared with those from approximate models yielding information on the reliability of the latter. Triples contributions are found to be very important, except for the π-complex, which has a UCCSD(T)/CBS relative enthalpy of -10.56 kJ/mol compared to infinitely separated propene + OH. The addition transition states are found to have relative enthalpies of -9.93 kJ/mol for the central and -9.84 kJ/mol for the terminal case. Allylic abstraction mechanisms, although lying significantly higher, still have only slightly positive barriers - a value of 3.21 kJ/mol for the direct and 1.67 kJ/mol for the consecutive case. Conventional transition state theory was used as a rough estimation for determining rate constants and turned out to agree well with experimental data.

Original languageEnglish
Pages (from-to)2313-2321
Number of pages9
JournalJournal of Chemical Theory and Computation
Volume5
Issue number9
DOIs
Publication statusPublished - Sep 2009

Fingerprint

Alkenes
alkenes
Olefins
Propylene
Enthalpy
Geometry
Vibrational spectra
enthalpy
Extrapolation
Rate constants
geometry
extrapolation
orbitals
optimization
propylene
hydroxide ion

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Computer Science Applications

Cite this

High accuracy ab initio calculations on reactions of OH with 1-alkenes. The case of propene. / Izsák, Róbert; Szori, Milán; Knowles, Peter J.; Viskolcz, B.

In: Journal of Chemical Theory and Computation, Vol. 5, No. 9, 09.2009, p. 2313-2321.

Research output: Contribution to journalArticle

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