Kinetics for the reactions of C₆H₅ with CH₃OH and C₂H₅OH: Comparison of theory and experiment

The kinetics of the C₆H₅ reactions with CH₃OH and C₂H₅OH have been measured by pulsed-laser photolysis/mass-spectrometry (PLP/MS) employing acetophenone as the radical source. Kinetic modeling of the benzene formed in the reactions over the temperature range 483-771 K allows us to reliably determine the total rate constants for H-abstraction reactions. In order to extend our temperature range down to 304 K we have also applied the cavity ring-down spectrometric technique using nitrosobenzene as the radical source. Both sets of data agree closely. A weighted least-squares analysis of the two complementary sets of data for the two reactions gave the total rate constants k(CH₃OH) = (7.82 ± 0.44) × 10¹¹ exp [-(853 ± 30)/T] and k(C₂H₅OH) = (5.73 ± 0.58) × 10¹¹ exp [-(1103 ± 44)/T] cm³ mol^-1 s^-1 for the temperature range studied. Theoretically, four possible product channels of the C₆H₅ + CH₃OH reaction producing C₆H₆ + CH₃O, C₆H₆ + CH₂OH, C₆H₅OH + CH₃ and C₆H₅COCH₃ + H and five possible product channels of the C₆H₅ + C₂H₅OH reaction producing C₆H₆ + C₂H₅O, C₆H₆ + CH₂CH₂OH, C₆H₆ + CH₃CHOH, C₆H₅OH + CH₃CH₂ and C₆H₅OCH₃ + H have been computed at the G2M//B3LYP/6-311+G(d, p) level of theory. The hydrogen abstraction channels were predicted to have lower energy barriers and their rate constants were calculated by the microcanonical variational transition state theory at 200-3000 K. The predicted rate constants are in good agreement with the experimental values.