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Reactions of methyl radicals with acetaldehyde and acetaldehyde-d1. II. BEBO calculations of the temperature dependence of the rate constants

✍ Scribed by T. BéRces; F. MáRta

Publisher
John Wiley and Sons
Year
1976
Tongue
English
Weight
527 KB
Volume
8
Category
Article
ISSN
0538-8066

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✦ Synopsis

The BEBO method was used to calculate the kinetic isotope effect for formyl-hydrogen abstraction from acetaldehyde by methyl radicals. The calculated isotope effect and experimental ratios of the rate constants obtained at 785'K for the reactions of CH3 with CHDCHO and CHDCDO, together with the theoretical temperature dependence of the specific rates (as formulated by the BEBO theory), were used to obtain rate constants for the steps CH3 + CH3CHO -+ CH, + CH3CO (2a), CH, + CH3CHO + CHI + CHtCHO (2b), and CH3 + CH3CDO ---$ CHID + CH3C0 (la) between 298 and 1224'K.

It was shown that the curvature apparent in the Arrhenius plot of the rate coefficient k p reported for the reaction of methyl radicals with acetaldehyde in the temperature range of 298-1224'K is caused both by the simultaneous contribution of steps (2a) and (2b) to methane formation, and by the curvature in the Arrhenius plots of the two elementary rate constants themselves. The predicted curve agrees well with the experimental data, especially if the tunneling correction is applied.

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