Hydrogen bonding between FNO and H2O: structure and energetics.

Nitrosyl fluoride, of some interest in atmospheric chemistry, has three atoms which could potentially serve as proton acceptors in the formation of hydrogen bonds. The optimized structure of FNO and H(2)O was determined at the MP4/6-31G** level of calculation. In the resulting structure, the hydrogen bonds at the fluorine with an energy of 5.15 kcal/mol, contrary to the prediction that less electronegative atoms make better proton acceptors/electron donors but consistent with results of proton affinity studies and with the contribution of a resonance structure with no bond between the N and F and a negative charge on the fluorine atom. The resulting structure also shows a significant increase in the length of the NF bond from 1.51 to 1.61 A.