Ab initio molecular orbital study of the [formula omitted] reaction

Abstract

A new mechanism of the C 2H 4+Cl 2→C 2H 4Cl 2 reaction in gas phase has been theoretically proposed using ab initio molecular orbital methods; Cl is abstracted from Cl 2 by C 2H 4, which leads first to the production of C 2H 4Cl+Cl radicals and then to immediate recombination to form C 2H 4Cl 2. It was predicted that this abstraction reaction, C 2H 4+Cl 2→C 2H 4Cl+Cl, is 25.1 kcal mol −1 endothermic with no transition state at the PMP4(SDTQ,full)/6-311++G(d,p)//MP2(fc)/6-31+G(d,p) level of theory. The previously proposed mechanism, direct Cl 2 addition to C 2H 4 to produce C 2H 4Cl 2, has also been examined and an energy barrier of 36.3 kcal mol −1 was obtained at the same level of theory. Therefore one concludes that the new mechanism is energetically more feasible than the direct Cl 2 addition to C 2H 4 for the C 2H 4+Cl 2→C 2H 4Cl 2 reaction in the gas phase.