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 ?
Chemical glycosylation via DNPy-glycosides having an [beta]-C=N moiety (in red) directly prepared by using the nucleophilicity of hemiacetal.
A selective nucleophilic attack of the anomeric hydroxy group to an electrophile is possible due to the stronger acidity of the hemiacetal.
in 1977 (6) to the "trichloroacetimidate method" where an O-C=N moiety could be constructed using the nucleophilicity of hemiacetals and activated by a protonic acid or B[F.
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.
In a paper published several months ago in the New England Journal of Medicine, Doctors Paul Jensen, Wentai Luo, James Pankow, Robert Strongin and David Peyton from Portland State University in the United States warned that harmful substances in the form of formaldehyde-containing hemiacetals may be formed during the heating and vaporization process of e-cigs.
Formaldehyde-releasing agents including hemiacetals, injure the respiratory tract causing a severe form of inflammation of the small airways in the lungs (bronchiolitis).
com/research/4310b0/the_2011_import_an) has announced the addition of the "The 2011 Import and Export Market for Acetals, Hemiacetals, and Their Halogenated, Sulfonated, Nitrated, or Nitrosated Derivatives in the United States" report to their offering.
On the demand side, exporters and strategic planners focusing on acetals, hemiacetals, and their halogenated, sulfonated, nitrated, or nitrosated derivatives in the United States face a number of questions.