Kinetics and mechanism for the C₆H₅ + CH₃CHO reaction: A computational and experimental study

The reaction of C₆H₅ radicals with CH₃CHO may be relevant to soot formation in its incipient stages. This reaction was studied computationally by the hybrid density functional theory calculations and experimentally by the cavity ring-down spectrometry (CRDS)to determine the overall kinetics. The result of the B3LYP/aug-cc-PVTZ//B3LYP/cc-PVDZ calculation indicated that the reaction could take place by many paths, similar to its analogous C₆H₅ reaction. As in the C₆H₅ + CH₂O reaction, the aldehydic H-abstraction reaction had the lowest reaction barrier, 0.5 kcal/mole (c.f. with that for the CH₂O reaction, 0.8 kcal/mole computed at the same level of theory); it should therefore dominate the reaction. Comparing the overall rate constant obtained by CRDS with that of the C₆H₅ + CH₂O reaction using the same method showed that the rate of the CH₃CHO reaction was much faster. The difference in the reactivity between the two aldehydes toward C₆H₅ was similar to that observed for their reactions with the OH radicals. Original is an abstract.