Aldehydes and ketones can be differentiated from non–carbonyl compounds through their reactions with derivatives of ammonia, semicarbazide, 2, 4–DNP. Hydrazine and hydroxylamine react with aldehydes and ketones to form precipitates. Semi carbazones and oximes are usually colourless. While  as 2,4–DNP derivatives are usually orange. The M.P. of these derivatives can also be used in identifying specific aldehydes and ketones. The ease with which aldehydes undergo oxidation provides a useful test that differentiates aldehydes from ketones