Among these functional groups, hydroxyl, carboxyl, phosphoric, hemiacetal
, and amino end groups have been proposed to reduce metal ions from the precursor salts to obtain the respective nanoparticles [52, 68, 104].
The anomeric acetyl group was hydrolyzed selectively using hydrazinium acetate, in DMF [29-31]; the resulting hemiacetal
was washed with water and brine and used without further purification.
Our first question focused on whether it could be possible to activate the hemiacetal
Caption: Figure 5: Suggested RN[H.sub.2] and [Fe.sup.2+] or cytochrome c- mediated conversion of cholesterol 5-hydroperoxide (29) to secosterol aldehyde A (30) via dioxetane (32), hydroperoxyvinyl ether (33) and the corresponding vinyl hemiacetal
, or secondary ozonide (34).
For M19, the product ions m/z 144 and m/z 244 in the MS/MS spectrum suggest a carboxyl function at the defluorinated pentyl chain and further biotransformation at the TMCP ring, which probably is the formation of a hemiacetal
structure of a hydroxyl group at the 2' position and a reactive aldehyde group at the 3' position.
Cellobiose has 8 free alcohol (OH) groups, 1 acetal linkage, and 1 hemiacetal
linkage, which give rise to strong inter- and intramolecular hydrogen bonds (Figure 2).
If a disaccharide contains a reactive hemiacetal
center, it is a reducing disaccharide.
Strong acids convert aflatoxin to its hemiacetal
form through hydration that is much less toxic.
The students expect to see a mass spectrum of the aldehyde but actually observe formation of the acetal or hemiacetal
and are asked to provide a mechanism to explain their results.
O equilibrio entre aldeidos livres, hemiacetal
e acetal, e influenciado pelo pH e pela concentracao de alcool etilico (Piggott & Conner, 2003) e tambem pelo tipo de madeira do tonel.
The C3 peak is mainly due to hemiacetal
carbon of cellulose and hemicelluloses and, to a lower extent, to carbonyl groups.
Seib, (1997) suggested that aldehyde groups initially generated by low levels of oxidant formed hemiacetal
cross links in oxidized starch, which stabilized the swelling of starch granules and also reduced its solubility as the crosslinks would prevent the amylopectin molecules from leaching out (Wang and Wang, 2003).
Pyranoses are formed by the reaction between an alcohol and an aldehyde forming a hemiacetal
. This hemiacetal
contains an asymmetric carbon atom and therefore can exist in two stereo isomeric form.
Sin embargo, estos resultados no coinciden con los reportados por Monticello y Finnerty (1985) y Kodama et al., (1973), quienes encontraron 3-hidroxi-2-formil benzotiofeno, 3-oxo-[3'-hidroxi-tionaftenil-(2)-metileno]-dihidrotionafteno y las formas hemiacetal
y trans del acido 4-[2-(3-hidroxi)-tianaptenil]-2-oxo-3-butenoico, los cuales son encontrados en la ruta metabolica de Kodoma.
This occurs through hemiacetal
linkages between hydroxyl groups of cellulose/hemicellulose and aldehyde groups formed at C6 primary hydroxyl groups of cellulose by the TEMPO-mediated oxidation.