Quantum chemical investigation of low-temperature intramolecular hydrogen transfer reactions of hydrocarbons

Jim Pfaendtner, Xinrui Yu, Linda J. Broadbelt*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

49 Scopus citations

Abstract

The B3LYP functional was evaluated as a method to calculate reaction barriers and structure-reactivity relationships for intramolecular hydrogen transfer reactions involving peroxy radicals. Nine different basis sets as well as five other MO/DFT and hybrid methods were used in comparing three reactions to available experimental data. It was shown that B3LYP/6-311+G(d,p) offers a good compromise between speed and accuracy for studies in which thermodynamic and kinetic data of many reactions are required. Sixteen reactions were studied to develop structure-reactivity relationships to correlate the activation energy with the heat of reaction. As long as no structural heterogeneities were present in the transition state ring, a simple EvansPolanyí relationship was shown to capture the activation energy as a function of heat of reaction for reactions in the 1,5-hydrogen shift family. For peroxy radicals undergoing self-abstraction of a hydrogen atom in the 1,5-position, the activation energy was calculated as E a (kcal mol -1) = 6.3 + ΔH rxn (kcal mol -1). For reactions with a carbonyl group embedded in the ring of the transition state, the activation energy of peroxy radicals undergoing self-abstraction was correlated as E a (kcal mol -1) = 18.1 + 0.74*ΔH rxn (kcal mol -1). The impact of the size of the transition state ring on the activation energy and pre-exponential factor was also probed, and it was shown that these effects can be described using simple nonlinear and linear fits, respectively.

Original languageEnglish (US)
Pages (from-to)10863-10871
Number of pages9
JournalJournal of Physical Chemistry A
Volume110
Issue number37
DOIs
StatePublished - Sep 21 2006

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

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