Analyses of Drugs and Chemicals by Infrared Absorption Spectroscopy. IX. : Determination of Naphthol Isomers in Mixtures by Compensation Method

An infrared spectrophotometric method is proposed for a rapid determination of a small amount of β-naphthol in α-naphthol or α-naphthol in β-naphthol, by the use of a compensation technique. Carbon disulfide is chosen as a solvent in both cases, and key bands used for β-naphthol and α-naphthol are 743 and 768 cm-1, and each component can be determined up to 0.1% and 0.5%, respectively. It was clarified that the absorption intensities of the CH out-of-plane bending bands in β-naphthol were influenced by the formation of an intermolecular hydrogen bonding.