Alvin H. Nielsen

The Infrared Absorption of the OH Group of Phenol

The fundamental vibrational band of the OH group of phenol appearing in the region of 3μ has been studied for solutions of different concentrations of phenol in benzene, bromobenzene, nitrobenzene, dioxane, and ethyl acetate. The band appears at the same position, 2.96μ, for the concentrated solutions in all the solvents. In dilute solution in benzene and bromobenzene it appears at 2.79μ. The band at 2.79μ is attributed to the OH of single molecules, while that appearing at 2.96μ in the more concentrated solutions is thought to be due to associated OH. In dilute solutions in the oxygenated solvents the band appears at wavelengths longer than 2.79μ and is more intense than for the corresponding solution in benzene or bromobenzene. These results are regarded as evidence that the oxygenated solvents form weak additive compounds with the phenol by sharing the proton of the OH group.