Conversion to carboxylic acids [H2O]

Definition

Treatment of acid chlorides with water leads to the formation of carboxylic acids. This is called hydrolysis of acid chlorides.

Explanation

Acid chlorides react with water, often violently, to give the corresponding carboxylic acids and hydrogen chloride as a by-product. This by-product can often produce an undesired reaction, so the pyridine is used to convert the hydrogen chloride into pyridinium chloride (unreactive form). This is a simple example of addition-elimination reaction.

The mechanism of this transformation consists of three steps. In the first step, water function as a nucleophile and attacks the carbonyl carbon. In the second step, the carbonyl group is re-formed by expelling a chloride ion which is a good leaving group. And in the last step, the positive charge of the oxygen is removed by protonation and the carboxylic acid is formed.