OHphenol⋯OHalcohol hydrogen-bonding as the preferred hydrogen-bonded interaction in the crystal structures of three isomers of methylolphenol: analysis of hydrogen-bonding interactions in phenol and alcohol containing molecules

The crystal structures of three isomers containing a phenol and an alcohol functional group, 2-methylolphenol (1), 3-methylolphenol (2) and 4-methylolphenol (3) are reported. All isomers feature heteromeric hydrogen bonded interactions, either from the phenol hydrogen to the alcohol O or from the alcohol hydrogen to the phenol O. There are no homomeric interactions present in the solid state. An analysis of 31 related compounds shows that in the literature the OHphenol⋯OHalcohol hydrogen bond is the most commonly seen heteromeric interaction in these types of compounds, and DFT calculations show that this hydrogen bond has the highest interaction energy in the three isomers. The isomer 3-methylolphenol (2) crystallizes as two concomitant polymorphs, 2a containing two molecules in the asymmetric unit, and 2b containing three molecules in the asymmetric unit, with the former slightly more stable according to DFT calculations.