Aldose A monosaccharide that contains an aldehyde group

Aldose A monosaccharide that contains an aldehyde group. 

Monosaccharides that contain an aldehyde group are called aldoses, whereas those containing a ketone group are ketoses. Monosaccharides are also classified by the number of carbon atoms as trioses, tetroses, etc. objective 5 (Section 7.4), Exercise 7.22. Most natural monosaccharides belong to the d family. 

Monosaccharides containing three-, four-, five-, and six-carbon atoms are called trios-es, tetroses, pentoses, and hexoses, respectively. Monosaccharides that contain an aldehyde group on one carbon atom and a hydroxyl group on each of the other carbon atoms are called aldoses. Ketoses are monosaccharides that contain a ketone group on one carbon atom and a hydroxyl group on each of the other carbons. 

We restrict discnssion here to simple monosaccharides, i.e., polyhydroxy compounds that contain a carbonyl fnnctional gronp (Chap. 3). There are two series, the aldoses that contain an aldehyde group and... 

Monosaccharides have the general formula C H2 0 , with one of the carbons being the carbonyl group of either an aldehyde or a ketone. The most common monosaccharides have from three to nine carbon atoms. The suffix indicates that a molecule is a carbohydrate, and the prefixes trir, tetr-, pent-, and so forth, indicate the number of carbon atoms in the chain. Monosaccharides containing an aldehyde group are classified as aldoses those containing a ketone group are classified as ketoses. 

The monosaccharide D-glucose, whose chemistry is representative of all aldoses containing four or more carbon atoms, exists predominantly in the two pyranosc forms 4 and 5. These are six-membered hemiacetals formed by the reversible cyclization of the acyclic polyhydroxy aldehyde 3 (Eq. 23.1). In the cyclic forms 4 and 5, the ring carbon that is derived from the carbonyl group is referred to as the anomeric carbon atom. The specific rotation, [a] (Sec. 7.5), of a-D-(+)-glucose (4) is +112 whereas that of the -anomer 5 is +19°. When crystals of either pure 4 or pure 5 are dissolved in water, the [a]p changes to an equilibrium value of +52.7°. This process is termed mutarotation. At equilibrium in water, the a- and p-forms are present in the ratio of 36 64 only about 0.03% of D-glucose is in the acyclic form 3. 

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