In organic chemistry, a ketose is a monosaccharide containing one ketone (>C=O) group per molecule. The simplest ketose is dihydroxyacetone ((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. Ketoses that are bound into glycosides, for example in the case of the fructose moiety of sucrose, are nonreducing sugars.
bonded oxygen.
Chemistry
Ketoses and aldoses can be chemically differentiated through Seliwanoff's test, where the sample is heated with acid and resorcinol. 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: (the basis for KDO)
- Nonoses: (the basis for neuraminic acid)
References
- Lindhorst, Thisbe K. (2007). Essentials of Carbohydrate Chemistry and Biochemistry (1st ed.). Wiley-VCH. ISBN 978-3-527-31528-4.
- Robyt, John F. (1997). Essentials of Carbohydrate Chemistry (1st ed.). Springer. ISBN 0-387-94951-8.
- McMurry, John E. (2010-01-01). Organic Chemistry: With Biological Applications. Cengage Learning. p. 880. ISBN 978-0495391449.
- "Seliwanoff's Test". Harper College. Archived from the original on 2017-12-16. Retrieved 2011-07-10.
In organic chemistry a ketose is a monosaccharide containing one ketone gt C O group per molecule The simplest ketose is dihydroxyacetone 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 Ketoses that are bound into glycosides for example in the case of the fructose moiety of sucrose are nonreducing sugars Fructose an example of a ketose The ketone group is the double bonded oxygen ChemistryKetoses and aldoses can be chemically differentiated through Seliwanoff s test where the sample is heated with acid and resorcinol 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 ketosesFamily tree of D ketoses up to hexoses dihydroxyacetone 1 D erythrulose 2 D ribulose 3a D xylulose 3b D psicose 4a D fructose 4b D sorbose 4c D tagatose 4d 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 the basis for KDO Nonoses the basis for neuraminic acid ReferencesLindhorst Thisbe K 2007 Essentials of Carbohydrate Chemistry and Biochemistry 1st ed Wiley VCH ISBN 978 3 527 31528 4 Robyt John F 1997 Essentials of Carbohydrate Chemistry 1st ed Springer ISBN 0 387 94951 8 McMurry John E 2010 01 01 Organic Chemistry With Biological Applications Cengage Learning p 880 ISBN 978 0495391449 Seliwanoff s Test Harper College Archived from the original on 2017 12 16 Retrieved 2011 07 10
