Reaction of Methylene with Dichloromethane and Nonequilibrium Unimolecular Elimination Reactions of 1,1-C2H4Cl2 and 1,1,2-C2H3Cl3 Molecules

The gas-phase reaction of methylene with dichloromethane proceeds by Cl and H abstraction. The two reactions are competitive, although the ratio of rates depends upon the excess energy carried by the methylene and its electronic state. The total rates of reaction of CH2 with CH2Cl2 and with C2H4 are comparable. The methyl, chloromethyl, and dichloromethyl radicals that are generated by the CH2 abstraction reactions form a good chemical activation system for studying the HCl elimination reactions of C2H5Cl, 1,2-C2H4Cl2, 1,1-C2H4Cl2, and 1,1,2-C2H3Cl3 at energies of ∼90 kcal mole−1. The results for the first two molecules agree with previous work; the rate constants for 1,1-C2H4Cl2 and 1,1,2-C2H3Cl2 are 1.2×1010 and 3.4×108 sec−1, respectively. Unusual ``disproportionation''-type reactions in which chloroethenes and HCl are directly formed seem to occur between dichloromethyl and methyl or chloromethyl radicals.