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Every simple monosaccharide has an acyclic (open chain) form, which can be written as (()) (=) (()); that is, a straight chain of carbon atoms, one of which is a carbonyl group, all the others bearing a hydrogen -H and a hydroxyl-OH each, with one extra hydrogen at either end.
Monosaccharides are the simplest units of carbohydrates and the simplest form of sugar. If the carbonyl is at position 1 (that is, n or m is zero), the molecule begins with a formyl group H(C=O)− and is technically an aldehyde. In that case, the compound is termed an aldose.
Osazone formation was developed by Emil Fischer, [3] who used the reaction as a test to identify monosaccharides. The formation of a pair of hydrazone functionalities involves both oxidation and condensation reactions. [4] Since the reaction requires a free carbonyl group, only "reducing sugars" participate.
The conventional numbering of the carbons in the closed form is the same as in the open-chain form. If the sugar is an aldohexose, with the carbonyl in position 1, the reaction may involve the hydroxyl on carbon 4 or carbon 5, creating a hemiacetal with five- or six-membered ring, respectively.
They are composed of two monosaccharide units bound together by a covalent bond known as a glycosidic linkage formed via a dehydration reaction, resulting in the loss of a hydrogen atom from one monosaccharide and a hydroxyl group from the other. The formula of unmodified disaccharides is C 12 H 22 O 11. Although there are numerous kinds of ...
Thus the structure of the linear form is H–(CHOH) x –C(=O)–(CHOH) 4-x –H, where x is 0, 1, or 2. The term "pentose" sometimes is assumed to include deoxypentoses, such as deoxyribose: compounds with general formula C 5 H 10 O 5-y that can be described as derived from pentoses by replacement of one or more hydroxyl groups with hydrogen ...
Compound sugars, also called disaccharides or double sugars, are molecules made of two bonded monosaccharides; common examples are sucrose (glucose + fructose), lactose (glucose + galactose), and maltose (two molecules of glucose). White sugar is a refined form of sucrose. In the body, compound sugars are hydrolysed into simple sugars.
Fischer projection of D-glyceraldehyde. Like most carbohydrates, simple aldoses have the general chemical formula C n (H 2 O) n.Because formaldehyde (n=1) and glycolaldehyde (n=2) are not generally considered to be carbohydrates, [1] the simplest possible aldose is the triose glyceraldehyde, which only contains three carbon atoms.