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In organic chemistry, a hemiacetal is a functional group the general formula R 1 R 2 C(OH)OR, where R 1, R 2 is a hydrogen atom or an organic substituent. They generally result from the nucleophilic addition of an alcohol (a compound with at least one hydroxy group ) to an aldehyde ( R−CH=O ) or a ketone ( R 2 C=O ) under acidic conditions.
Hemiacetals of ketones (sometimes called hemiketals) are even less stable than those of aldehydes. However, cyclic hemiacetals and hemiacetals bearing electron withdrawing groups are stable. Electron-withdrawing groups attached to the carbonyl atom shift the equilibrium constant toward the hemiacetal.
Generic structure of acetals. In organic chemistry, an acetal is a functional group with the connectivity R 2 C(OR') 2.Here, the R groups can be organic fragments (a carbon atom, with arbitrary other atoms attached to that) or hydrogen, while the R' groups must be organic fragments not hydrogen.
Structural chemistry is a part of chemistry and deals with spatial structures of molecules (in the gaseous, liquid or solid state) and solids (with extended structures that cannot be subdivided into molecules). For structure elucidation [1] a range of different methods is used.
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The β-D-glucopyranosyl group which is obtained by the removal of the hemiacetal hydroxyl group from β-D-glucopyranoseIn organic chemistry, a glycosyl group is a univalent free radical or substituent structure obtained by removing the hydroxyl (−OH) group from the hemiacetal (−CH(OH)O−) group found in the cyclic form of a monosaccharide and, by extension, of a lower oligosaccharide.
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This reaction converts anhydroglucopyranoside subunits to cyclic hemiacetal structures, which can be reacted with amine groups to form a Schiff base linkage (a carbon-nitrogen double bond). These linkages are unstable and will easily dissociate. Sodium cyanoborohydride (NaBH 3 CN) can be used as a stabilizer by reducing the linkages back to an ...