Mutarotation

Mutarotation is a chemical phenomenon in the field of chemistry and biochemistry involving the change in the optical rotation because of the change in the equilibrium between two anomers, when the corresponding stereocenters interconvert. Cyclic sugars show this property.

Mechanism

Mutarotation occurs due to the presence of an anomeric carbon in the cyclic hemiacetal form of monosaccharides. The process involves the temporary opening of the ring structure to the straight-chain form, followed by a reversal of the ring-forming reaction in a different direction, leading to the formation of a different anomer.

Factors affecting Mutarotation

The rate of mutarotation is affected by the temperature and the pH of the solution. The process is faster at higher temperatures and varies with pH. Each sugar has a characteristic equilibrium constant, known as the mutarotation constant.

Examples

D-glucose exhibits mutarotation as it has an anomeric carbon that can exist in either the alpha or the beta form. The alpha form has the -OH on carbon 1 below the plane of the ring, and the beta form has the -OH on carbon 1 above the plane.

See also

• Anomer
• Monosaccharide
• Optical rotation

Mutarotation

• Α- and β-D-glucopyranose
  Α- and β-D-glucopyranose
• 
  General mutarotation mechanism