The general features of the mechanism of the over-all process [Formula: see text][Formula: see text] are similar to those for the over-all process [Formula: see text][Formula: see text] studied previously. The reaction is inhibited by HCl. Chains are terminated by two processes, one of which is first order, the other second order in atomic chlorine. The first order process is not entirely diffusion controlled and a theory is advanced to account for its nature; the homogeneous combination of chlorine atoms requires a third body, mono- and di-chloromethyl chloroformate being particularly effective. The activation energy for hydrogen abstraction from monochloromethyl chloroformate by atomic chlorine is 5.2 kcal. per mole. The C—H bond dissociation energy in monochloromethyl chloroformate is estimated to be 99.8 ± 4.5 kcal. per mole.