Theoretical investigation of the hydrogen bonding interaction between substituted phenols and simple O- and N-bases

The hydrogen bond interaction between substituted phenols (X = NH2, CH3, H, Cl, CN, NO2) and O-bases (HOF, H2O, CH3OH, (CH3)2O) or N-bases (NHF2, NH2F, NH3, CH3NH2) is investigated theoretically at the B3LYP/6-31++G(d,p) level. The calculations include the optimized geometries, the interaction energies, the frequency shifts of the ν(OH) stretching vibration along with relevant NBO parameters such as the charges on the atoms, the occupation of antibonding orbitals and the second-order hyperconjugation energies. The role of both the deprotonation enthalpies of the proton donor O-H bonds of phenols and the proton affinities of the O- or N-bases are explored. The differences between the OH⋯O and OH⋯N hydrogen bonds are outlined.