Structures, energetics and fragmentation pathways of CnH2 2+ carbodications

Potential energy curves have been calculated for CnH22+ (n = 2-9) ions and results have been compared with data on unimolecular charge-separation reactions obtained by Rabrenović and Beynon. Geometry-optimized, minimum energy, linear CnH22+ structures have been computed for ground and low-lying excited states. These carbodications exist in stable configurations with well depths greater than 3 eV. Decomposition pathways into singly charged fragment ions lead to products with computed kinetic energies in excess of 1 eV. A high degree of correlation exists between experimental information and results computed for linear CnH22+ structures having hydrogen atoms on each end. The exception involves C4H22+ reactions where a low-lying doubly charged isomer must be invoked to rationalize the experimental data. © 1985.