부산대학교 도서관

In an effort to elucidate the nature of general reactions between carbynes and hydrocarbons, the reactants, products and transition state for the reaction of methylidyne (CH) with methane (CH4) have been characterized using ab-initio quantum-mechanical methods. Both the self-consistent field (SCF) method and the method of configuration interaction of including single and double excitations (CISD) were employed initially. The largest basis used was a triple-zeta plus double-polarization plus f-functions basis (TZ2P + f). All levels of theory predict that this reaction proceeds through a transition state of Cs symmetry. With the TZ2P + f basis, the SCF method predicts an activation energy of 25.8 kcal mol-1 while CISD predicts 9.5 kcal mol-1. Coupled cluster methods including all single and double excitations (CCSD) applied to the optimized TZ2P + f CISD geometries yield an activation energy of 5.8 kcal mol-1. When connected triple excitations are added perturbatively to the CCSD energy (CCSD(T)), the activation energy is further reduced to 4.3 kcal mol-1. The estimated exact activation energy is 3.5 +/- 0.5 kcal mol-1. [ABSTRACT FROM AUTHOR]