The behavior of cellulose,amylose, and β-d-xylan towards anhydrous hydrogen fluoride

Cellulose, amylose, and d-glucose are converted into α-d-glucopyranosyl fluoride (3) when dissolved in anhydrous hydrogen fluoride. The fluoride subsequently undergoes condensation to afford a mixture of ligosaccharides, probably via an oxocarbonium ion. The fluoride 3 and the oligosaccharides are in an equilibrium, which was studied by ¹³C-n.m.r. spectroscopy; in dilute solution in hydrogen fluoride, the d-glucosyl fluoride is the main product present, but when the hydrogen fluoride is evaporated, the equilibrium is shifted towards the oligosaccharides. These constitute a complex mixture which was studied by methylation and subsequent analysis of the methylated alditols derived therefrom. (1→4)-β-d-Xylan and d-xylose behave similarly to the d-glucose derivatives towards hydrogen fluoride.