Reactions at high pressure. Part 8. The mechanisms of acid catalysed hydrolyses of glycosides

Abstract

Rates of acid-catalysed hydrolysis for 19 glycosides, both furanosides and pyranosides, have been measured at pressures between 1 and 1 500 bar.‡ Volumes of activation have been determined for these reactions and were found to show a markedly parallel trend to the entropies of activation for the same reactions. In particular, alkyl furanosides have ΔV– 2 to –10 cal K^–1 mol^–1§ while the corresponding pyranosides have ΔV= 10–17 cal K^–1 mol^–1. It is inferred that the former react by an A2 mechanism and the latter by an A1 type.