• ab initio;
  • potential energy surface;
  • cyanoethenyl cation;
  • G3X theory;
  • interstellar chemistry


Geometries and energies of 15 stable C3H3N+ structures, potential intermediates in ion–molecule reactions that occur on the C3H3N+ potential energy surface (PES), have been calculated with G3X theory. Accurate energy ordering of the intermediates is needed to understand the initial stage of the reactions. The reactions of N(2D) with cyclopropenyl cation and of HCN and HNC with acetylene cation radical are of interest because they may lead to the formation of cyanoacetylene or some of its isomers in dense interstellar dust clouds. The energetics of the initial phases of these reactions are discussed in light of the calculated energies of reactants and intermediates. The variety of high-energy intermediates optimized makes it likely that the reactions discussed involve long-lived complexes and multiple rearrangements. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006