Reactions of N-Propylbenzene During Gas Phase Oxidation

Flow reactor data from the oxidation of n-propylbenzene near 1060 K are analyzed to deduce the reactions involved in removing the n-propyl group. Three major routes are found: (i) abstraction of a hydrogen from the propyl group followed by decomposition of the radical and oxidative reactions, (ii) displacement of the propyl group by a radical species, and (iii) direct cleavage of the sidechain followed by the oxidation of the benzyl radical. The reaction sequences beginning with the abstraction of primary and benzylic hydrogens from the propyl group show a strong analogy to results for the oxidation of propane. However, the products predicted based on the analogy to propane for the abstraction of secondary hydrogens from the propyl group were not detected in significant quantities. The absence of expected products led to the recognition that a rapid phenyl shift isomerization of the beta-phenyl propyl radical occurs prior to the decomposition of the radical.