Ab initio study of the mechanism for the thermal decomposition of the phenoxy radical

Ruifeng Liu*, Keiji Morokuma, Alexander M. Mebel, Ming-Chang Lin

*Corresponding author for this work

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106 Scopus citations

Abstract

Various ab initia methods have been applied to the studies of the molecular structure and energetics for the low-lying electronic states of the phenoxy radical and of the mechanism of its thermal decomposition. The calculations confirm the decomposition mechanism I (Scheme 1) suggested earlier from experimental consideration. It involves the formation of the bicyclic intermediate E2 followed by α-CC bond cleavage to produce E3 and the elimination of the CO group from the latter leading to the main reaction products, C5H5 + CO. The rate-determining step is E2 → E3 with transition state T2. The activation energy, 52 kcal/mol, at our best G2M(rcc,MP2) level, is 8 kcal/mol higher than the value derived from experiment. A multistep RRKM calculation has been performed for the decomposition reaction. The theoretical rate constants agree well with the experimental results at lower temperatures (T < 1200 K) but deviate from experiment above 1300 K. Plausible reasons for the deviation have been discussed. On the basis of state-specific and state-averaged CASSCF calculations, the observed electronic transitions for the phenoxy radical have been assigned.

Original languageEnglish
Pages (from-to)9314-9322
Number of pages9
JournalJournal of physical chemistry
Volume100
Issue number22
DOIs
StatePublished - 1 Dec 1996

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