A ketose is a monosaccharide containing one ketone group per molecule.
With three carbon atoms, dihydroxyacetone is the simplest of all ketoses and is the only one having no optical activity. Ketoses can isomerize into an aldose when the carbonyl group is located at the end of the molecule. Such ketoses are reducing sugars.
All ketoses listed here are 2-ketones:Trioses: dihydroxyacetone
Pentoses: ribulose, xylulose
Hexoses: fructose, psicose, sorbose, tagatose
Octoses: D-manno-octulose (the basis for KDO)
Nonoses: D-glycero-D-galacto-nonulose (the basis for neuraminic acid)
General qualitative reaction for ketoses is Seliwanoff's test.