CLEAPSS Supporting practical science and technology
PP011 - Testing for carbonyl compounds with Fehling's solution
Although both aldehydes and ketones contain the carbonyl functional group (-C=O), only aldehydes give a positive test (formation of an orange to brick-red precipitate of copper(I) oxide) with Fehling’s solution. This small-scale Fehling’s ‘test’ is a useful qualitative analysis technique for detecting the presence of aldehydes and reducing sugars.