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Aldehyde structure. In organic chemistry, an aldehyde (/ ˈ æ l d ɪ h aɪ d /) is an organic compound containing a functional group with the structure R−CH=O. [1] The functional group itself (without the "R" side chain) can be referred to as an aldehyde but can also be classified as a formyl group. Aldehydes are a common motif in many ...
Reducing disaccharides like lactose and maltose have only one of their two anomeric carbons involved in the glycosidic bond, while the other is free and can convert to an open-chain form with an aldehyde group. The aldehyde functional group allows the sugar to act as a reducing agent, for example, in the Tollens' test or Benedict's test.
A typical monosaccharide has the structure H–(CHOH) x (C=O)–(CHOH) y –H, that is, an aldehyde or ketone with many hydroxyl groups added, usually one on each carbon atom that is not part of the aldehyde or ketone functional group. Examples of monosaccharides are glucose, fructose, and glyceraldehydes.
An aldose is a monosaccharide (a simple sugar) with a carbon backbone chain with a carbonyl group on the endmost carbon atom, making it an aldehyde, and hydroxyl groups connected to all the other carbon atoms. Aldoses can be distinguished from ketoses, which have the carbonyl group away from the end of the molecule, and are therefore ketones.
There are few examples of seven-carbon sugars in nature, among which are: sedoheptulose or D-altro-heptulose (a ketose), an intermediate in the Calvin cycle and in lipid A biosynthesis [1] [2] mannoheptulose (a ketose), found in avocadoes [3] L-glycero-D-manno-heptose (an aldose), a late intermediate in lipid A biosynthesis. [4]
It is a sweet, colorless, crystalline solid that is an intermediate compound in carbohydrate metabolism. The word comes from combining glycerol and aldehyde, as glyceraldehyde is glycerol with one alcohol group oxidized to an aldehyde. [4]
Xylose (cf. Ancient Greek: ξύλον, xylon, "wood") is a sugar first isolated from wood, and named for it.Xylose is classified as a monosaccharide of the aldopentose type, which means that it contains five carbon atoms and includes an aldehyde functional group.
For example, the aldohexose glucose may form a hemiacetal linkage between the aldehyde group on carbon 1 and the hydroxyl on carbon 4, yielding a molecule with a 5-membered ring, called glucofuranose. The same reaction can take place between carbons 1 and 5 to form a molecule with a 6-membered ring, called glucopyranose.