Ab Initio Investigation of Proton Transfer in Ammonia− Hydrogen Chloride and the Effect of Water Molecules in the Gas Phase

Abstract:

The gas-phase proton-transfer reaction of ammonia−hydrogen chloride and the effect of the first three water molecules are investigated by high-level ab initio calculations on the molecular clusters NH3−HCl−(H2O)n, n = 0, 1, 2, 3. The equilibrium structures, binding energies, and harmonic frequencies of the clusters as well as the potential energy surfaces along the proton-transfer pathway of ammonia−hydrogen chloride are calculated at the second-order Møller−Plesset perturbation (MP2) level with the extended basis set 6-311++G(d,p). Either without water or with one water molecule, the ammonia−hydrogen chloride system exists as a usual hydrogen-bonded complex. With two or three water molecules, the system becomes an ion pair resulting from the complete transfer of a proton from hydrogen chloride to ammonia. The potential energy surfaces along the proton-transfer pathway are examined to understand …

Año de publicación:

1998

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