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The ketone group is the double-bonded oxygen. In organic chemistry, a ketose is a monosaccharide containing one ketone (>C=O) group per molecule. [1] [2] The simplest ketose is dihydroxyacetone ((CH 2 OH) 2 C=O), which has only three carbon atoms. It is the only ketose with no optical activity.
For many monosaccharides (including glucose), the cyclic forms predominate, in the solid state and in solutions, and therefore the same name commonly is used for the open- and closed-chain isomers. Thus, for example, the term "glucose" may signify glucofuranose, glucopyranose, the open-chain form, or a mixture of the three.
Many ketones are cyclic. The simplest class have the formula (CH 2) n CO, where n varies from 2 for cyclopropanone ((CH 2) 2 CO) to the tens. Larger derivatives exist. Cyclohexanone ((CH 2) 5 CO), a symmetrical cyclic ketone, is an important intermediate in the production of nylon.
The monosaccharides can be divided into two groups: the aldoses, which have an aldehyde group, and the ketoses, which have a ketone group. Ketoses must first tautomerize to aldoses before they can act as reducing sugars. The common dietary monosaccharides galactose, glucose and fructose are all reducing sugars.
They generally result from the nucleophilic addition of an alcohol (a compound with at least one hydroxy group) to an aldehyde (R−CH=O) or a ketone (R 2 C=O) under acidic conditions. The addition of an alcohol to a ketone is more commonly referred to as a hemiketal. Common examples of hemiacetals include cyclic monosaccharides.
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.
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.
In chemistry, a hexose is a monosaccharide (simple sugar) with six carbon atoms. [1] [2] The chemical formula for all hexoses is C 6 H 12 O 6, and their molecular weight is 180.156 g/mol. [3] Hexoses exist in two forms, open-chain or cyclic, that easily convert into each other in aqueous solutions. [4]
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