Ab initio study of the mechanism for the thermal decomposition of the phenoxy radical
- Emory Univ., Atlanta, GA (United States)
Various ab initio 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 {alpha}-CC bond cleavage to produce E3 and the elimination of the CO group from the latter leading to the main reaction products, C{sub 5}H{sub 5} + CO. The rate-determining step is E2 {yields} 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 transition for the phenoxy radical have been assigned. 63 refs., 10 figs., 4 tabs.
- DOE Contract Number:
- FG05-91ER14191
- OSTI ID:
- 263183
- Journal Information:
- Journal of Physical Chemistry, Vol. 100, Issue 22; Other Information: PBD: 30 May 1996
- Country of Publication:
- United States
- Language:
- English
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