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.