Ab Initio Reaction Enthalpies for Some Gas-Phase Acid-Base Neutralizations

摘要

Several factors that contribute to the enthalpy of the gas-phase of a proton with Hydroxyl radical and Cyanide radical as derived from ab initio computations were examined. These include the convergence of the Moller-Plesset perturbation series, nuclear-motion corrections, diffuse basis functions, and details of optimizing the molecular structures. Satisfactory results were obtained only when diffuse functions and at least third-order perturbation (MPS) were employed. The same was found to be true for the protonation of Methyl radical, Carboxyl radical, Methoxy radical and Nitrate radical. Large basis sets and MP4 or CI approximations to the energies gave accuracies for HO- and CN- within 2 kcal/mol.