Both aldehydes and ketones contain the carbonyl group (>C=O). The carbonyl group can be confirmed by:

  1. 2,4-dinitrophenyl hydrazine (2,4-DNP test)
  2. Sodium bisulphite

2, 4 - DNP Test

The organic compound is treated with 2,4-DNP reagent and warmed over a water bath. Formation of yellow or orange crystals indicate the presence of a carbonyl group (aldehydic or ketonic).

Sodium Bisulphite Test

The organic compound is treated with a saturated solution of soduim bisulphite. The mixture is shaken well and left for 15 minutes. The formation of a crystalline precipitate indicates the presence of a carbonyl group.