Abstract
The rates of hydrolysis of substituted phenyl α-and β-D-mannopyranosides were measured in acidic and alkaline solutions. In 0.11N hydrochloric acid solution, the α-mannosides were hydrolyzed faster than the corresponding β-anomers. The rates of hydrolysis for the α-mannosides were unaffected by substitution in the phenyl group (Hammett reaction constant ρ=-0.07±0.065 (S. D.)), and those for the β-mannosides were slightly enhanced by the introduction of electron-releasing substituents (ρ=-0.25±0.082). In sodium hydroxide solution, the α-mannosides liberated their aglycones, phenols, much faster than the corresponding β-anomers and the rates were enhanced by the introduction of electron-withdrawing substituents (ρ=+2.7±0.14 for the α-, +3.1±0.46 for the β-mannosides, each in 3.93N NaOH). Phenyl α-mannoside was hydrolyzed much faster than phenyl β-glucoside, though both have trans-1, 2 configuration, indicating the importance of a 1, 2-diaxial orientation for the reaction.
