A b i n i t i o study of the hydrogen bonding interactions of formamide with water and methanol

Abstract

Ab initio calculations of hydrogen bond energies for a number of water–formamide and methanol–formamide complexes are reported at both the SCF and correlated levels. Full gradient optimizations of these structures have been performed for basis sets of double zeta and double zeta plus polarization quality. For both water and methanol, the most stable 1:1 complex is found to be a cyclic double hydrogen bonded structure. Basis set effects on the calculated hydrogen bond energies were investigated as was the magnitude of the basis set superposition error. In all cases investigated, the addition of polarization functions to the basis set is found to decrease the calculated binding energy by approximately 2–4 kcal/mol, while correlation is found to increase the binding energy by ≂1 kcal/mol. Calculations on dihydrated formamide indicate a small three‐body contribution to the total binding energy.