REACTION OF CARBON-ATOMS WITH H2CL- AN AB-INITIO STUDY OF A POSSIBLE INTERSTELLAR PROCESS( )

An ab initio study of the reaction of carbon atoms with H2Cl+ ions has been carried out at the G1 level. The (H2CCl)(+) species on the tripl et surface have been characterized and their molecular structure discu ssed. It is found that the approach through a hydrogen atom is favored over approach toward chlorine. The former leads in a first step to a CHClH+ species, which finally leads to the more stable HCClH+ and H2CC l+ species. These isomers are quite stable relative to the reactants, about 64 and 79 kcal mol(-1), respectively. Contrary to what was previ osuly assumed, the CH+ + HCl channel is not possible in the interstell ar medium, since it is clearly endothermic, whereas production of CCl + H-2 is only slightly exothermic. We predict that the dominant chann els should be the production of HCCl+ + H and of Cl + CH2+, which are both exothermic (by more than 42 and 20 kcal mol(-1), respectively, at the G1 level) and proceed without an activation barrier. The HCCl+ io n may be a precursor of interstellar CCl through dissociative recombin ation.