Excitation Energies of Chemically Activated Isobutane and Neopentane and the Correlation of Their Decomposition Rates with Radical Recombination Rates

Intermolecular comparisons of the total insertion and addition rates of singlet‐state methylene radicals with several alkanes, alkenes, and alkylsilanes indicate that for most reactants the singlet‐state methylene radicals carry the same fraction of any initial excess energy into their insertion or addition products. Attempts to correlate decomposition rates of chemically activated isobutane and neopentane with estimated alkyl radical recombination rates require high critical energies for decomposition, “tight” radical models, and activated complex models with free internal rotations which give thermal decomposition $A$ factors of ∼ 10¹⁷ sec⁻¹.