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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 table shows all aldoses with 3 to 6 carbon atoms, and a few ketoses. For chiral molecules, only the ' D-' form (with the next-to-last hydroxyl on the right side) is shown; the corresponding forms have mirror-image structures. Some of these monosaccharides are only synthetically prepared in the laboratory and not found in nature.
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 ...
Glucose is a monosaccharide containing six carbon atoms and an aldehyde group, and is therefore an aldohexose. The glucose molecule can exist in an open-chain (acyclic) as well as ring (cyclic) form. Glucose is naturally occurring and is found in its free state in fruits and other parts of plants.
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.
In these compounds, hydrogen can form in the +1 and -1 oxidation states. Hydrogen can form compounds both ionically and in covalent substances. It is a part of many organic compounds such as hydrocarbons as well as water and other organic substances. The H + ion is often called a proton because it has one proton and no electrons, although the ...
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.