Ketose
bonded oxygen.
In organic chemistry, a ketose is a monosaccharide containing one ketone (Page Module:Chem2/styles.css has no content.>C=O) group per molecule.[1][2] The simplest ketose is dihydroxyacetone (Page Module:Chem2/styles.css has no content.(CH2OH)2C=O), which has only three carbon atoms. It is the only ketose with no optical activity. All monosaccharide ketoses are reducing sugars, because they can tautomerize into aldoses via an enediol intermediate, and the resulting aldehyde group can be oxidised, for example in the Tollens' test or Benedict's test.[3] Ketoses that are bound into glycosides, for example in the case of the fructose moiety of sucrose, are nonreducing sugars.[3]
Chemistry
Ketoses and aldoses can be chemically differentiated through Seliwanoff's test, where the sample is heated with acid and resorcinol.[4] The test relies on the dehydration reaction which occurs more quickly in ketoses, so that while aldoses react slowly, producing a light pink color, ketoses react more quickly and strongly to produce a dark red color. Ketoses can isomerize to aldoses through the Lobry-de Bruyn-van Ekenstein transformation.
Examples of ketoses
All ketoses listed here are 2-ketoses, in other words, the carbonyl group is on the second carbon atom from the end:
- Trioses: dihydroxyacetone
- Tetroses: erythrulose
- Pentoses: ribulose, xylulose
- Hexoses: fructose, psicose, sorbose, tagatose
- Heptoses: sedoheptulose
- Octoses: Page Template:Smallcaps/styles.css has no content.d-manno-octulose (the basis for KDO)
- Nonoses: Page Template:Smallcaps/styles.css has no content.d-glycero-Page Template:Smallcaps/styles.css has no content.d-galacto-nonulose (the basis for neuraminic acid)
References
Page Template:Reflist/styles.css has no content.
- ^ Page Module:Citation/CS1/styles.css has no content.Lindhorst, Thisbe K. (2007). Essentials of Carbohydrate Chemistry and Biochemistry (1st ed.). Wiley-VCH. ISBN 978-3-527-31528-4.
- ^ Page Module:Citation/CS1/styles.css has no content.Robyt, John F. (1997). Essentials of Carbohydrate Chemistry (1st ed.). Springer. ISBN 0-387-94951-8.
- ^ a b Page Module:Citation/CS1/styles.css has no content.McMurry, John E. (2010-01-01). Organic Chemistry: With Biological Applications. Cengage Learning. p. 880. ISBN 978-0495391449.
- ^ Page Module:Citation/CS1/styles.css has no content."Seliwanoff's Test". Harper College. Archived from the original on 2017-12-16. Retrieved 2011-07-10.
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