Comparative Studies of Brown Coal and Lignin. I. Infra-Red Spectra

Abstract

The infra-red spectra of two softwood lignins are discussed with reference to the spectra of their acetyl and methoxyl derivatives. The spectra of the respective acetyl derivatives provide conclusive evidence for the presence of both phenolic and alcoholic groups in lignin and oxidized lignin, and of alcoholic groups only in the methoxyl derivatives of both these samples. Treatment of lignin with hydriodic acid in the conventional Zeisel determination of methoxyl groups eliminates the alcoholic hydroxyl groups and appears to split aliphatic ether linkages. The spectrum of lignin treated with hydriodic acid is very similar to that of brown coal, which supports previous chemical evidence that brown coal appears to be essentially " demethylated dehydrated lignin ". The progress of the isolation of lignin from wood was followed by infra-red spectroscopy.