Knowledge Bank

“The molecular complexes formed by hydrogen bonding between phenol molecules have been studied, the emphasis being placed on determination of thermodynamic properties. The association of phenol in carbon tetrachloride at various concentrations was followed by observing the intensity of the first overtone of the $O-H$ stretching vibration of the monomeric phenol molecule. These measurements were carried out at temperatures from $15-60\circ C$. Due to experimental error, no conclusions can yet be drawn about the thermodynamic properties of the dimer. For the formation of trimer from monomer, the measured properties are: \Delta{H}{13}^{0}=-6.7\mbox{ Keal}\Delta {S}{13}^{0}=-18\mbox{ cal deg}^{-1} Overlapping of the association band with the monomer band makes uncertain any measurement at the high concentrations required for determination of the properties of higher polymers. Certain considerations lead to the conclusion that the phenol polymers are cyclic. Hence, the heat of formation of a hydrogen bond in a cyclic phenol trimer is $-2.2$ Keal.”