Theoretical study on the thermal decomposition and isomerization of 3-Me-1-heptyl radical.

A detailed theoretical investigation on the thermal decomposition and isomerization of 3-Me-1-heptyl radical is performed at the ab initio CBS-QB3 level of theory. The calculation reveals that the detailed reaction mechanisms of 3-Me-1-heptyl radical mainly incorporate reversible intramolecular hydrogen atom transfer and the beta-site C C bond scission. The standard reaction enthalpies ( Δ r H 298 0 ) and enthalpies of formation ( Δ f H 298 0 ) are determined at the CBS-QB3 level of theory. All investigated decomposition reactions are generally endothermic, while most of the isomerization processes are exothermic. Among the hydrogen atom transfer processes, the 1,3- and 1,2-hydrogen atom migration (R 5 and R 6 , respectively) are prohibited due to their high isomerization barriers, while the 1,6-(R 2 ) and 1,5-hydrogen atom transfer (R 3 ) are kinetically accessible (owing to their low ring strains in the cyclic transition states). Compared with the 1,5-hydrogen atom shift for the n -heptyl radical, the methyl-substitution increases the rate coefficient by a factor of about 3.0. The product distributions are predicted at different temperatures on the basis of the steady-state approximation (SSA). The ultimate and dominant products majorly include ethylene (C 2 H 4 ), propylene (C 3 H 6 ), 1-butylene (1-C 4 H 8 ) and 2-hexene (2-C 6 H 12 ) over the temperature range of 500–2500 K. [ABSTRACT FROM AUTHOR]