betaDglucopyranose

Beta-D-glucopyranose is the beta anomer of D-glucopyranose, the six-membered cyclic hemiacetal form of D-glucose. It arises when the aldehyde group at carbon 1 reacts intramolecularly with the hydroxyl group at carbon 5 to form a pyranose ring. In this beta form, the anomeric hydroxyl group at C1 is oriented equatorially upward in the standard chair conformation (4C1). The designation D indicates the configuration at carbon 5, the penultimate carbon of the chain.

In aqueous solution, beta-D-glucopyranose and its alpha counterpart interconvert through mutarotation, opening the ring to the open-chain aldehyde and reclosing to cyclic forms. At room temperature, the equilibrium mixture is typically about two-thirds beta and one-third alpha, with small amounts of other furanose forms and ongoing mutarotation kinetics.

As a monosaccharide, beta-D-glucopyranose has the molecular formula C6H12O6 and is a reducing sugar, since it can revert to the open-chain aldehyde form. It is a fundamental building block in biology: in cellulose, glucose units are linked by β(1→4) bonds and thus exist predominantly as beta-D-glucopyranose; in starch and glycogen, the polymers are composed largely of alpha-D-glucose units. The beta anomer serves as a standard reference form in carbohydrate chemistry and is frequently studied to understand mutarotation and the formation of glycosidic bonds.