Gas‐phase ozonolysis of cis‐ and trans‐dichloroethylene

Publisher Website
Google Scholar
Abstract
Dichloroethylene (DCE), either cis or trans, was reacted with O3 at 23°C in both N2 and O2 buffered mixtures. Both reactant consumption and product formation were monitored by infrared spectroscopy and, in some cases, O3 consumption was monitored by ultraviolet absorption. For thoroughly dried mixtures, the initial products were only HCClO and O2, but geometrical isomerization also occurred. The stoichiometry of the overall reaction always was equation image The HCClO was unstable and disappeared slowly in a first‐order reaction which was, at least in part, heterogeneous. The products were CO and HCl so that the stoichiometric reaction was equation image The rate law was complex. The rate was always faster in N2 than in O2. In the N2 buffered reaction, inhibition occurred as the reaction progressed and O2 was produced. From the reactant and product decay curves, the following rate behavior was established: equation image where high and low concentrations are relative terms for the initial pressure ranges covered ([DCE]0 = 0.21−78.4 torr, [O3]0 = 0.30−6.76 torr). The rate coefficients k2, k3, and k4 were larger for the trans‐DCE than the cis‐DCE, and for each isomer they were larger in N2 than in O2 buffered reactions.The ozonolysis can be explained in terms of the mechanism equation image equation image where R2 is DCE, RO is HCClO, and RO2 is HCClO2. Rate ceofficients are computed.The isomerization is first order in [O3] and approximately first order in [DCE] for the limited kinetic data we were able to obtain. The isomerization does not appear to be explained by the reverse reactions of reactions (6), (7), and (9). Presumably isomerization occurs through some other route.

This publication has 10 references indexed in Scilit: