Acid Halides

Acid chlorides are the most reactive of the carboxylic acid derivatives.  In general, we can convert acid halides into to any of the other carboxylic acid derivatives.

Take Note

Naming Acid Chlorides

Acid chlorides are named by replacing "ic acid" of the corresponding carboxylic acid with "yl chloride.

For example;

Hydrolysis of Acid Chlorides

Like all carboxylic acid derivatives reactions of them with water results in hydrolysis to carboxylic acids.  Even neutral water will react with acid chlorides since they are such good electrophiles.


Alcoholysis of Acid Chlorides

In an analogous reaction, acid chlorides react with alcohols to form esters.  The mechanisms is exactly like that for hydrolysis.

Pyridine is often used to neutralize the acid as it is formed.  It forms a salt, pyridinium chloride, that can be easily removed with water extractions, and prevents acid sensitive parts of the molecule form reacting with the acid.


Aminolysis of Acid Chlorides

Reactions of ammonia or amines with acid chlorides results in the formation of amides.  The mechanism is as you would expect analogous with that of esters and water with acid halides.

Two equivalents of amine are required since the byproduct HCl will react with one equivalent to form ammonium chloride.

Here is an example with aniline.

Reduction of Acid Chlorides

Acid chlorides can be reduced with LiAlH4 to form alcohols.

The reduction proceeds through the corresponding intermediate aldehyde which is rapidly reduced to the alcohol.  Recall that aldehydes are readily reduced to alcohols with LiAlHso the aldehyde can not be obtained using LiAlH4.

To obtain the aldehyde one can use Lithium tri(t-butoxy) aluminum hydride.

For example, the reduction of benzoyl chloride with Lithium tri(t-butoxy) aluminum hydride followed by an acid water workup yields the aldehyde.