AB-INITIO STUDY OF THE FORMATION OF C3H3+ FROM THE REACTION OF CH3+ WITH ACETYLENE

Ab initio molecular orbital theory has been used to study the mechanis m of the formation of C3H3+ from the reaction of CH3+ with acetylene. The highest level geometry optimizations and frequencies were computed at MP2-FC/6-31G* single point energies of all the critical structure s were computed to the MP4-FC/6-31G*//MP2-FC/6-31G** theory level. On e of the three alternative transition structures leading to the format ion of C3H3+ gives the cyclopropenyl cation and the other two the prop argyl cation. The proportions of C3H2D+ and C3HD2+ obtained when CD3reacts with acetylene, and the composite nature of the metastable peak observed for the [C3H5](+) --> [C3H3](+) + H-2 fragmentation are expl ained by assuming a different degree of deuterium scrambling depending on the energy of the system. (C) 1996 by John Wiley & Sons, Inc.