Inorganic chemistry, aketose is amonosaccharide containing oneketone (>C=O) group permolecule.[1][2] The simplest ketose isdihydroxyacetone ((CH2OH)2C=O), which has only three carbon atoms. It is the only ketose with nooptical activity. All monosaccharide ketoses arereducing sugars, because they cantautomerize intoaldoses via anenediol intermediate, and the resulting aldehyde group can beoxidised, for example in theTollens' test orBenedict's test.[3] Ketoses that are bound intoglycosides, for example in the case of the fructosemoiety ofsucrose, are nonreducing sugars.[3]
Ketoses and aldoses can be chemically differentiated throughSeliwanoff's test, where the sample is heated with acid andresorcinol.[4] The test relies on thedehydration 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 canisomerize to aldoses through theLobry-de Bruyn-van Ekenstein transformation.
All ketoses listed here are 2-ketoses, in other words, thecarbonyl group is on the second carbon atom from the end:
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