hemiacetal


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hemiacetal

[¦he·mē′as·ə‚tal]
(organic chemistry)
A class of compounds that have the grouping 〉C(OH)‒(OR) and that result from the reaction of an aldehyde and alcohol.
References in periodicals archive ?
Additionally, related to similar mechanisms involved during synthesis and stabilization of metal nanoparticles reported with other EPSs, it has been described abundant functional groups as hydroxyl and hemiacetal ends in EPSs that carried out the reduction and stabilization of nanoparticles making them more suitable for application in different fields of study [86, 89].
There are three kinds of hydroxy groups in a saccharide moiety, the hemiacetal, the primary hydroxy group, and the secondary hydroxy groups (Fig.
Hamberg, "Hydroperoxide lyases (CYP74C and CYP74B) catalyze the homolytic isomerization of fatty acid hydroperoxides into hemiacetals," Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids, vol.
M22, which shows the same fragments as the other 3 metabolites, is probably generated by hemiacetal formation followed by glucuronidation.
Each cellulose chain possesses a directional chemical asymmetry with respect to the termini of its molecular axis: one end is a chemically reducing functionality (i.e., a hemiacetal unit) and the other has a pendant hydroxyl group, the nonreducing end.
This observation also supports the decreased solubility observed for [oxAYBS.sup.*] which has been attributed to formation of crosslinks by hemiacetals that may be formed by low levels of oxidants.
All chemical reactions occur at hemiacetal bond and/or hydroxyl groups, which determine chemical properties of cellulose.
In contrast, more than 99% of aldosterone cyclizes, with the alde- hyde group at carbon 18 reacting with the hydroxyl at carbon 11, forming a stable 11,18 hemiacetal.
The initially formed hemiacetal 16.5 transforms, depending on the conditions, into a hydrate, hemiacetal, or enol form (Fig.
CO oxidation is the simplest model system understood by a simplified CO + [[O].sup.*] [right arrow] C[O.sub.2] mechanism, while for C[H.sub.3]C[H.sub.2]OH oxidation on an oxide support the reactions are very complicated: C[H.sub.3]C[H.sub.2]OH [right arrow] C[H.sub.3]C[H.sub.2]O(ad) + H(ad), C[H.sub.3]C[H.sub.2]O(ad) + [[O].sup.*] [right arrow] C[H.sub.3]CHO, C[H.sub.3]CHO + [[O].sup.*] [right arrow] C[H.sub.3]COOH, and ethyl acetate (C[H.sub.3]COOC[H.sub.2]C[H.sub.3]) formation via aldehyde and hemiacetal (C[H.sub.3]CH(OH)O[C.sub.2][H.sub.5]).
El espectro de 13C CP-MAS NMR muestra un pico a 92 ppm correspondiente al hemiacetal producto de la oxidacion con peryodato.
The peaks characteristic of TPF were the broad absorption band of the stretching vibration of the hydroxyl groups (-OH) in cellulose, starch, and glycerol (3307-3292 [cm.sup.-1]); the hemiacetal bonds from the starch Hour (1638-1650 [cm.sup.-1]); the vibration peak corresponding to the cyclic -C-C- of the glucose (1030-1018 [cm.sup.-1]) in the starch; and the 1151, 924, and 860 [cm.sup.-1] peaks corresponding to the fingerprint region of the banana starch.