High Temperature Alkaline Degradation of Phenyl β-D-Glucopyranoside

Reaction rates and product distributions have been determined for the degradation of phenyl β-D-glucopyranoside in aq. alkali under various conditions. The effects of a stronger nucleophile, variations in hydroxide ion concentration at constant ionic strength, changes in temperature, and the level of 18O incorporation from the solvent into the product phenol were investigated. The degradation rate decreased greatly for the 2-O-methyl analog. The results indicate that, at both 100 and 170°C, phenyl β-D-glucopyranoside degradation proceeded by an SNicB(2) reaction. At both temperatures the expected SNicB(2) product, levoglucosan, formed in less than quantitative yields because of competing reactions which occurred after the rate-determining step.