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In [[sugar]] [[chemistry]], an '''anomer''' is a special type of [[epimer]]. It is a [[stereoisomer]] ([[diastereomer]], more exactly) of a [[saccharide]] (in the cyclic form) that differs only in its configuration at the [[hemiacetal]] (or [[hemiketal]]) carbon, also called the '''anomeric carbon'''.  If the structure is analogous to one with the [[hydroxyl group]] on the anomeric carbon in the [[cyclohexane conformation|axial position]] of glucose, then the sugar is an alpha anomer.  If, however, that hydroxyl is equatorial, the sugar is a beta anomer.  For example, α-<small>D</small>-glucopyranose and β-<small>D</small>-glucopyranose, the two cyclic forms of [[glucose]], are anomers.

[[Image:glucoseab.jpg|thumb|500px|The α- and β-anomers of D-glucopyranose.]] 
The [[anomeric effect]] helps stabilize the α-anomer. The term for interconversion between the two anomers is [[mutarotation]].

The two different anomers are two distinct chemical structures, and thus have different physical and chemical properties, notably [[optical rotation]]. For example, α-D-[[glucose]] has an optical rotation of +112 degrees and its anomer, β-D-glucose, has an optical rotation of +19 degrees.

== See also ==
*[[Anomerization]]
*[[Haworth projection]]

== External links ==
*[http://www.sinica.edu.tw/~ccswww/zj-BI-1999-P.283.pdf Chin. Chem. Soc., Vol. 46(3) 283 (1999)] ''On the Assignment of Anomeric Configuration'' (pdf)
*http://www.cem.msu.edu/~reusch/VirtualText/carbhyd.htm

{{Carbohydrates}}

[[Category:Stereochemistry]]
[[Category:Carbohydrates]]

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[[it:Anomeria]]
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[[ja:アノマー]]
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[[ru:Аномеры]]


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