The effect of a carbon-carbon double bond on the energy required for decomposition in an electron beam-generated plasma reactor is studied by comparing the decomposition of trichloroethylene and 1,1,1-trichloroethane. A reaction mechanism for TCE decomposition based on a chlorine radical chain reaction is presented which accounts for the formation of all of the experimentally observed reaction products. TCE decomposition is autocatalyzed by reaction products, whereas TCA decomposition is inhibited. The rate expression for the decomposition of TCE in the reactor is determined to be r = -[T](15.07[T-0](-0.40) + 0.006 {[T-0]-[T]}), where [T] and [T-0] are both in ppm, and r is in ppm Mrad(-1). The energy expense epsilon for TCE decomposition is determined as a function of inlet concentration. For 99% decomposition of 100 ppm TCE in air, epsilon = 28 eV/molecule, and epsilon = 2.5 eV/molecule at 3000 ppm. This is only 2.5-5% of the amount of energy required to decompose a similar amount of TCA as reported by the authors in a previous study. By comparing the energy requirements for TCE decomposition to those for TCA decomposition, the TCE reaction chain length is determined to increase from approximately 20 at 100 ppm initial TCE concentration, to 40 at 3000 ppm.