Single-Pulse Shock Tube Studies on the Thermal Decomposition of n-Butyl Phenyl Ether, n-Pentylbenzene, and Phenotole and the Heat of Formation of Phenoxy and Benzyl Radicals

Article abstract of DOI:10.1021/j100371a023

n-Butyl phenyl ether, n-pentylbenzene, and phenotole have been decomposed in single-pulse shock tube experiments.The main reaction for all these processes involves bond cleavage leading to the formation of an alkyl and a resonance-stabilized radical.In the case of n-butyl phenyl ether decomposition, a molecular mechanism involving the direct formation of 1-butene has also been detected.The rate expressions for the decomposition processes are k(n-C4H9-OC6H5 -> n-C4H9 + C6H5O) = 1.0 * 10¹⁶ exp(-33000/T) s^-1, k(n-C4H9-OC6H5 -> 1-C4H8 + C6H5OH) = 4.0 * 10¹³ exp(-28900/T) s^-1, k(n-C4H9-CH2C6H5 -> n-C4H9 + CH2C6H5) = 1 * 10¹⁶ exp(-36500/T) s^-1, and k(n-C2H5-OC6H5 -> C2H4 + C6H5OH and C2H5 + C6H5O) = 5.7 * 10¹⁵ exp(-32300/T) s^-1 over the temperature range of 940-1100 K and pressures of 2-3 atm.The assumption that the primary C-H bond strength for butane is 421.5 kJ mol^-1 leads to heat of formation of the phenoxy radical of 55.3 kJ mol^-1 and that of benzyl radical, 203 kJ mol^-1.The A factors for the bond cleavage reactions are all significantly higher than previously reported for analogous processes.In the case of the benzyl-forming process they are now in accord with combination rates and the geometric mean rule.