Thermal decomposition of methyl phenyl ether in shock waves: The kinetics of phenoxy radical reactions

The unimolecular decomposition of methyl phenyl ether (anisole) was studied in incident shock waves covering the temperature range from 1000 to 1580 K and the pressure range from 0.4 to 0.9 atm. The CO formed in the reaction, monitored by resonance absorption using a stabilized CW CO laser, could be satisfactorily accounted for by a four-reaction mechanism: C₆H₅OCH₃ → C₆H₅O + CH₃ (1), C₆H₅O → CO + C₅H₅ (2), CH₃ + C₆H₅O → o- and p-CH₃C₆H₄OH (3), and CH₃ + CH₃ → C₂H₆ (4). Kinetic modeling of observed CO production profiles based on the above mechanism with 70 sets of data led to k₁ ≃ (1.2 ± 0.3) × 10¹⁶ exp(-33 100/T) s^-1, k₂ = 10^11.40±0.20 exp(-22 100 ± 450/T) s^-1, and k₃ = (5.5 ± 2.0) × 10¹¹ cm³·mol^-1·s^-1. The relatively low A factor and activation energy measured for the phenoxy radical decomposition reaction support the mechanism A involving a tight intermediate.