The Reaction of O3 with CCl2CH2

The gas-phase reaction of O3 with CCl2CH2 at 25 °C was studied by monitoring O3 consumption by ultraviolet absorption and product formation and olefin consumption by infrared absorption. In the absence or presence of excess N2, and for initial olefin-to-O3 ratios, [CCl2CH2]0/[O3]0, in excess of 20 ([O3]0 ~ 1.0 Torr), the rate law is[Formula: see text]with k = 2.4 × 106 M−2 s−1. At lower olefin-to-O3 ratios, the rate is initially more rapid than predicted by the above equation, but follows the equation after the reaction has proceeded for some time. In the presence of excess O2, the rate is markedly reduced, and the rate law becomes[Formula: see text]with k′ = 2.2 M−1 s−1.The products of the reaction are CCl2O, HCOOH, CH2ClCCl(O), CO, O2, HCl, and presumably H2O. In the absence of O2, the CCl2CH2-to-O3 consumption ratio approaches 2, but the CCl2O produced per O3 consumed is between 0.25 and 0.4. With excess O2, the latter ratio becomes unity, but the CCl2CH2-to-O3 consumed approaches 5.The results are interpreted in terms of a chain mechanism with CCl2O2 as the chain carrier. The mechanism developed explains the main features of the reaction.