Theoretical study of CH...O hydrogen bonds in H2O-CH3F, H2O-CH2F2, and H2O-CHF3
Ab initio methods have been used to study the CH...O hydrogen bond between H2O and CH3F, CH2F2, and CHF3. The calculations have been carried out using the 6-31G**, 6-311G* and 6-311++G** basis sets at the MP2 and MP4 levels of theory. Interaction energies include basis set superposition error adjustments. The results show that the strongest CH...O hydrogen bond is the bisector one with the lone pairs on the oxygen. The inclusion of each additional fluorine results in a systematic strengthening of the hydrogen bond by 1 kcal/mol as well as in the shortening of the hydrogen bond distance by 0.1 Angstrom.