(d) Fehling’s Test:
Fehling’s solution is a complex compound of Cu2+. When the aldehyde compound is treated with Fehling’s solution Cu2+ is reduced to Cu+ and the aldehyde is reduced to acids. During the reaction, a red precipitate is formed.
Fehling's Test
Aromatic aldehydes do not respond to Fehling’s test. An aqueous solution of the compound may be used instead of an alcoholic solution. Formic acid also gives this test.
Note: The appearance of red precipitate confirms the presence of an aldehydic group.
