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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.
Pages in category "Hemiacetals" The following 2 pages are in this category, out of 2 total. This list may not reflect recent changes. H. Hemiacetal; P. Paraformaldehyde
In contrast to variations of R, both R' groups are organic fragments. If one R' is a hydrogen, the functional group is instead a hemiacetal, while if both are H, the functional group is a ketone hydrate or aldehyde hydrate. Formation of an acetal occurs when the hydroxyl group of a hemiacetal becomes protonated and is lost as water.
Common conformations are chair (C), boat (B), skew (S), half-chair (H) or envelope (E). The ring atoms are then numbered; the anomeric, or hemiacetal, carbon is always 1. Oxygen atoms in the structure are, in general, referred to by the carbon atom they are attached to in the acyclic form, and designated O. Then:
It undergoes rapid polymerization, including forming a hemiacetal cyclic dimer.Under alkaline conditions, it undergoes a rapid aldol condensation.. Hydroxyacetone can be produced by degradation of various sugars.
The design of new ligands is usually based on the modification of known ligands for the target proteins. Proteases are enzymes that catalyze hydrolysis of a peptide bond. These proteins have evolved to recognize and bind the transition state of peptide hydrolysis reaction which is a tetrahedral intermediate.
An oligosaccharide has both a reducing and a non-reducing end. The reducing end of an oligosaccharide is the monosaccharide residue with hemiacetal functionality, thereby capable of reducing the Tollens’ reagent, while the non-reducing end is the monosaccharide residue in acetal form, thus incapable of reducing the Tollens’ reagent. [2]
The chemical structure of cellobiose is derived from the condensation of a pair of β-glucose molecules forming a β(1→4) bond. It can be hydrolyzed to glucose enzymatically or with acid. Cellobiose has eight free alcohol (OH) groups, one acetal linkage, and one hemiacetal linkage, which give rise to strong inter- and intramolecular hydrogen ...