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hemiacetal

Pronunciation: hem'e-as'e-tal

Definition: RCH(OH)OR', a product of the addition of an alcohol to an aldehyde (an acetal is formed by the addition of an alcohol to a hemiacetal). In the aldose sugars, the hemiacetal formation is internal and labile, brought about by the 4-OH or 5-OH attack on the carbonyl oxygen, thus yielding the furanose or pyranose structures; the hemiacetal forms of the sugars are involved in all polysaccharides, as glycosyl residues or glycosides.

See Also: hemiketal, acetal

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© Copyright 2018 Wolters Kluwer. All Rights Reserved. Review date: Sep 19, 2016.

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