Theoretical Studies of Proton-Transfer Reactions. I. Reactions of Hydride Ion with Hydrogen Fluoride and Hydrogen Molecules

Computations of the potential energy surfaces for the reactions of hydride ion with hydrogen molecule in the symmetrical reaction, and with hydrogen fluoride to produce hydrogen and fluoride ion, have been carried out by the LCAO-MO-SCF method using Gaussian basis functions. All integrals are analytically evaluated, and no approximations other than those inherent in the LCAO-MO-SCF method are used. The calculated energies are believed to be quite close to the Hartree-Fock limits. The reaction system H₃¯ is found to have a potential energy surface qualitatively similar to that for the neutral H₃ system, and an activation energy for the hydrogen-exchange reaction of ca. 15 kcal/mole is calculated. The H₂F¯ system has an unexpected potential energy surface in that no barrier is found along the minimum energy path between reactants and products. Instead, a minimum along the path is found indicating the existence of a stable H₂F¯ complex with an e ergy ca. 8 kcal below that for the separated fluoride ion and hydrogen molecule.