Kinetics of Chemically Activated Isobutane and Neopentane from the 4358- and 3660-Å Photolyses of Diazomethane with Propane and Isobutane

Abstract

The results of a study of chemically activated isobutane and neopentane produced by excited singlet-state methylene radical insertion into the secondary and tertiary C–H bonds of propane and isobutane, respectively, are reported. The methylene radicals were produced at two energies by the 4358- and 3660-Å photolyses of diazomethane. The measured decomposition rates for the energized isobutane are 1.9 × 107 and 3.6 × 107 sec−1 in the 4358- and 3660-Å photolysis systems, respectively, and for the energized neopentane are 4.4 × 106 and 6.8 × 106 sec−1 in the 4358- and 3660-Å photolysis systems, respectively. These rates correlate well via RRKM theoretical calculations with thermal A factors in the range of 1016.3–1016.9 sec−1 for isobutane and 1016.5–1016.9 sec−1 for neopentane.