View source for Anomers

Anomers are a kind of [[Diastereoisomer|diastereoisomers]]<ref>Berg J., Tymoczko J. and Stryer L. (2012) Biochemistry, 7th Edition, New York: Kate Ahr Parker. pg331</ref>. As the name suggests, they are [[Isomer|isomers]] of each other. 

There are 2 forms of anomers, namely alpha and beta. They are&nbsp;identified by the direction that the [[Hydroxyl group|-OH group is]] pointing to on the carbon1 on the cyclic [[Sugar|sugar]]. Thus, the [[Carbon|carbon]] is called an [[Anameric carbon|anameric carbon]]<ref>Berg J., Tymoczko J. and Stryer L. (2012) Biochemistry, 7th Edition, New York: Kate Ahr Parker. pg333</ref>. An alpha-glucose has its -OH perpendicular to the ring. A [[Beta-glucose|beta-glucose]] has its -OH parallel to the ring. It is possible to distinguish the two by the directions that the molecule rotates under plane-polarise light<ref>Cornell College (2012) Reactions of monosaccharides. Available at: http://www.cornellcollege.edu/chemistry/courses/cardon/organic/326chorxns.html (Last accessed 30.11.1012)</ref>. 

Alpha and beta anomers are formed from an open-chain sugar by mutarotation<ref>Professional Education,Testing and Certification Organization International (2012) Organic Chemistry 16.4 Cyclic Structures of Monosaccharides. Available at: http://www.peoi.org/Courses/Coursesen/chemorg/ch/ch16d.html (Last accessed 29.11.2012)</ref>.In the process of mutarotation, a solution of both anomers are&nbsp;heated at a high temperature, giving rise to individual monomers. The solution is then added into water. Through contact with water, the sugar monomers appear to be opening up their ring structure to form straight chain sugars. In addition, these straight chain sugars are converted back into its ring structure. The reaction is said to be at a dynamic [[Equilibrium|equilibrium]], where the rate of forward reaction is equal to the rate of backward reaction<ref>Professional Education,Testing and Certification Organization International (2012) Organic Chemistry 16.4 Cyclic Structures of Monosaccharides. Available at: http://www.peoi.org/Courses/Coursesen/chemorg/ch/ch16d.html (Last accessed 29.11.2012)</ref>.&nbsp;The percentages of each type of anomers present&nbsp;are as follow: 25% are alpha anomers and 75% are beta anomers<ref>Berg J., Tymoczko J. and Stryer L. (2012) Biochemistry, 7th Edition, New York: Kate Ahr Parker. pg333</ref>. Anomers in the form of [[Fischer projection|Fischer projection]] (open-chain sugar) makes up less than 1% of the total solution<ref>Russel KC (1999) Haworth Projections. Available at: http://www.nku.edu/~russellk/tutorial/sugar/haworth.html (Last accessed 30.11.2012)</ref>. 

Under a dynamic equilibrium, 6-carbon [[Pyranose|pyranose]] rings are usually formed as compared to 5-carbon [[Furanose|furanose]] rings<ref>Solano Community College (2007) Drawing Haworth Projections. Available at: http://mathsci.solano.edu/users/cspillne/Chem%2011%20Handouts%20and%20Worksheets/Unit%203/Drawing%20Haworth%20Projections.doc (Last accessed 29.11.2012)</ref>. 

[[Condensation Reaction|Condensation]] reaction catalyses the formation of [[Disaccharides|disaccharides]] between 2 monosaccharides with the elimination of a [[Water|water]] molecule. 

Determining which anomer is alpha and which is beta is easy when looking at the Haworth projection; alpha anomers have different stereochemistry at carbon 1 and carbon 5, whereas beta anomers have the same stereochemistry at carbon 1 and 5.

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