Aldehydes and Ketones, Summaries of Organic Chemistry

Download Aldehydes and Ketones and more Summaries Organic Chemistry in PDF only on Docsity! ORCHMD1 ORGANIC CHEMISTRY (Laboratory) Discussion Activity 23: Differential Tests for Aldehydes and Ketones ➢ contain the carbonyl group (–C=O), and hence they are collectively called carbonyl compounds ➢ The presence of the carbonyl group in both aldehydes and ketones is responsible for the similar behavior of aldehydes and ketones. ➢ However, the aldehydes, because of the presence of a free hydrogen atom in their molecules, are more reactive than ketones and hence differ from the latter in certain aspects. ✓ ALDEHYDES – RCH=O ✓ the carbonyl group is linked to an alkyl group and a hydrogen atom ✓ aldehydes contain the functional group – CHO known as aldehyde group ✓ R2C (= O) ✓ it is linked to two alkyl groups. ✓ ketones contain the functional group – C=O, known as the ketonic group. Oxidation ✓ Aldehydes only Reduction ✓ Aldehydes and Ketones Addition ✓ ✓ Aldehydes and Ketones ✓ Aldehydes are easily oxidized to carboxylic acids by a variety of oxidizing agents ✓ The formation of orange-yellow crystals indicates the presence of carbonyl group ORCHMD1 ORGANIC CHEMISTRY (Laboratory) Discussion ✓ The formation of crystalline precipitate confirms the carbonyl group ✓ Schiff reagent (Basic Fuchsin/Rosaniline hydrochloride) ✓ Used to detect for the presence of aldehyde ✓ Appearance of pink, red, and magenta color indicates the presence of aldehyde group ✓ 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. ✓ The appearance of red precipitate confirms the presence of an aldehydic group Fehling’s Reagent o Fehling’s A: aquaeous solution of deep blue copper (II) sulphate o Fehling’s B: colourless solution of Potassium sodium tartrate ✓ The tollens test for aldehydes is based on the ability of silver ions to oxidize aldehydes. ✓ Tollen’s reagent: Silver ammonia complex in ammonia solution [Ag(NH3)2]NO3 ✓ The appearance of shiny silver mirror confirms the presence of aldehydes