Carbonyl Compounds

The carbon oxygen double bond is a polar bond.

This leaves the carbon atom electron deficient and attractive to nucleophiles.

Cyanide is a nucleophile can be added across the carbonyl bond, this is a useful reaction for increasing the length of the carbon chain.

The resulting nitriles are hydrolysed by water in hot acid to form carboxylic acid.

Nitriles are reduced by sodium in ethanol to form an amine.

Tests for Carbonyl Compounds

Brady’s reagent produces bright orange crystals with carbonyl compounds.

The melting point of these crystals have very sharp melting points which can be looked up in data books to identify the original compound.

There are three tests for aldehyde:

1. Tollen’s reagent gives a silver mirror

2. Benedict’s solution gives a red precipitate

3. Acidified dichromate turns from orange to green

These rests are specific to aldehydes and not ketones!