Mutarotation

Mutarotation is the term given to the change in the specific rotation of plane polarized light, when it is passed through an aldohexose (a monosaccharide with six carbon atoms and H-C=O group). Mutarotation refers to the conversion of a pure anomer of a hemiacetal carbohydrate to an equilibrium mixture of two anomers.

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As the name suggests, it is the change in rotation ("Muta" means "Change").

Plane polarized light is obtained by passing ordinary light through a nicol prism.

During mutarotation, either α or β forms keep changing into the chain structure periodically to and fro.

Mutarotation also refers to the interconversion between the α and β anomers. However it must be converted to the open chain structure first before it can change conformation to the α or β position.

  For example, in glucose, carbon 1 (the aldehyde carbon) is the anomeric carbon. In fructose, carbon 2 (the keto carbon) is anomeric. Unlike the epimers, which are stable under ordinary conditions, anomers interconvert spontaneosly.