The Reaction of O₃ with CCl₂CH₂

Abstract

The gas-phase reaction of O 3 with CCl 2 CH 2 at 25 °C was studied by monitoring O 3 consumption by ultraviolet absorption and product formation and olefin consumption by infrared absorption. In the absence or presence of excess N 2 , and for initial olefin-to-O 3 ratios, [CCl 2 CH 2 ] 0 /[O 3 ] 0 , in excess of 20 ([O 3 ] 0 ~ 1.0 Torr), the rate law is[Formula: see text]with k = 2.4 × 10 6 M −2 s −1 . At lower olefin-to-O 3 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 O 2 , 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 CCl 2 O, HCOOH, CH 2 ClCCl(O), CO, O 2 , HCl, and presumably H 2 O. In the absence of O 2 , the CCl 2 CH 2 -to-O 3 consumption ratio approaches 2, but the CCl 2 O produced per O 3 consumed is between 0.25 and 0.4. With excess O 2 , the latter ratio becomes unity, but the CCl 2 CH 2 -to-O 3 consumed approaches 5.The results are interpreted in terms of a chain mechanism with CCl 2 O 2 as the chain carrier. The mechanism developed explains the main features of the reaction.