The Effects of Solvents on the IR and PMR Spectra of Intramolecular OH…π and OH…O Hydrogen Bonded Systems

The effects of solvents on the intramolecular OH…π and OH…O hydrogen bonding in 2-arylphenols and 2,6-diarylphenols have been studied by examining the OH stretching IR absorption spectra in a range of solvents. The solvent shifts of the hydrogen bonded bands, νOH…π and νOH…O, followed the G correlation and the BHW plot. The success of both correlations suggests that the solvent shifts are primarily due to a specific solvent-solute association, even in relatively non-polar solvents. The solvent sensitivity of the OH…π and OH…O hydrogen bonded bands depended on the stereo-chemical environment around the hydrogen bonded system rather than on such electronic factors as the strength of the hydrogen bonding. On the basis of the relationship between the solvent sensitivity and the structural changes over a group of phenols, a simplified model for the solvent-solute association is put forward. Furthermore, this simplified model is also discussed in terms of the aromatic solvent-induced shifts in the PMR spectra.