Experimental and theoretical studies of the phenyl radical reaction with propene.

The kinetics for the reaction of C6H5 with propene has been measured by cavity ring-down spectrometry (CRDS) at temperatures 296-496 K under an Ar pressure of 40 Torr. The total rate constant can be given by the following Arrhenius expression (in units of cm3 mol(-1) s(-1)): k(C6H5 + C3H6) = 10(11.93+/-0.06) exp[-(1512 +/- 51)/T]. Density functional and higher level of theory calculations (up to the G2M level) have been carried out to provide additional insights about the mechanism of this reaction, and we also performed transition state theory (TST) calculation for the rate constant prediction. Our theoretical kinetic calculations predict that the C6H5 addition to the terminal =CH2 site in propene is dominant at the temperature range of our CRDS measurements. However, the H-abstraction channel forming benzene and the allyl radical becomes increasingly important at higher temperatures. The total high-pressure limiting rate constant calculated on the basis of the G2M reaction barriers is in reasonable agreement with the experimental values.