hemiacetal


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Related to hemiacetal: Ketal

hem·i·ac·e·tal

(hem'ē-as'e-tăl),
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.

hem·i·ac·e·tal

(hem'ē-as'ĕ-tăl)
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 O, yielding the furanose or pyranose structures; the hemiacetal forms of the sugars are involved in all polysaccharides, as glycosyls or glycosides.
See also: hemiketal, acetal

hemiacetal

formed by nucleophilic addition of an alcohol to the carbonyl group of an aldehyde. Most open-chain hemiacetals are not stable, but cyclic hemiacetals of the type present in aldehyde sugars such as glucose are more stable.
References in periodicals archive ?
than nAYBS in the viscoAmylograph, reasons of which was attributed to probable formation of crosslinks by hemiacetals that may be formed by low levels of oxidants.
53) suggested that the saponin was actually a mixture of the 25R and 25S epimeric hemiacetals.
If desired, one can specifically look for potential reaction products, which, in the case of methanol (for example, in the fuel injector cleaner discussed in the prior section) would include dimethyl ether, formaldehyde, acetals and hemiacetals in addition to some hydrogen and carbon monoxide.