Mild oxidizing agents such as bromine water, silver oxide, sodium hypobromite etc. oxidize glucose to gluconic acid converting -CHO group to -COOH group.
Reducing sugars are easily oxidized to give carboxylic acid.
carbohydrates (having C=O) can be oxidised to carboxylic acids.
Such carbohydrates are classified as reducing sugars based on Benedicts or Fehlings tests
Aldoses (as they come from aldehydes)are readily oxidised.
In order for oxidation to occur, the cyclic form must first ring-open to give the reactive aldehyde.
Ketoses can also be reducing sugars because they can transform to (by tautomerisation) aldoses via an enediol.