Mechanism and Rate of Hydrogen Atom Attack on Toluene at High Temperature

Article abstract of DOI:10.1021/j100408a064

Hexamethylethane has been decomposed in the presence of large excesses of toluene and methane/toluene mixtures in single-pulse shock tube experiments in the temperature range of 950-1100 deg K and at 2-5 atm.Methane, ethane isobutene, and benzene are the main light hydrocarbon reaction products.At sufficiently high toluene/hexamethylethane ratio (>/= 100 to 1) the main reactions are hexamethylethane --> 2t-C4H9<*> (1); t-C4H9<*> --> H<*> + isobutene (2); H<*> + C6H5CH3 --> C6H6 + CH3<*> (4); H<*> + C6H5CH3 --> C6H5CH2<*> + H2 (5).From the yields of isobutene and benzene, we find k₅/k₄= 9.8exp(-1560/T).In the presence of sufficiently large excess of methane, benzene yields are reduced.This is due to the competitive process H + CH4 --> CH3 + H2 (7) and leads to k₇/k₅ = 1.95 exp(-2862/T).On the basis of k₇=2.4E11 exp(-7000/T) L/(mol s) (950-1100 deg K) we find k₄=1.2E10 exp(-2578/T) L/(mol s) and k₅=1.2E11 exp(-4138/T) L/(mol s).From the equilibrium constant, k_-4=1.2E9 exp(-8023/T) L/(mol s).