Carboxylic acids and their derivatives

Carboxylic Acids

Carboxylic acids are organic compounds that contain a carboxyl (COOH) functional group.
They have general formula CnH2n+1COOH.
Their naming uses the suffix -oic acid. For example, methanoic acid, ethanoic acid.
Carboxylic acids are characterised by their acidic properties. The –COOH group can lose a proton (H+) to form a carboxylate ion (-COO-).
They can form hydrogen bonds between molecules, leading to a higher boiling point than similar sized molecules that can only derive from weak van der Waals forces.
Carboxylic acids react with metals, bases, carbonates and alcohols.
When reacted with an alcohol in the presence of a strong acid catalyst, an ester is formed.

Acyl chlorides, also referred to as acid chlorides, are derived from carboxylic acids. They replace the –OH group of the carboxylic acid with a –Cl, creating a carboxyl chloride (COCl) group.
They have the general formula CnH2n+1COCl.
Their naming convention is similar to carboxylic acids, but using the suffix -oyl chloride instead. For example, ethanoyl chloride.
Acyl chlorides are considered as derivatives of carboxylic acids.
Despite their derived status, acyl chlorides are significantly more reactive than their parent carboxylic acids, particularly towards nucleophiles.
They can react with water, alcohols, and amines to produce carboxylic acids, esters, or amide respectively.

Esters are derived from carboxylic acids and an alcohol. They contain a carbonyl (C=O) group adjacent to an ether (R-O-R) group.
They have the general formula R-COO-R’.
Use the suffix -oate. Include name of the alcohol-derived part first, then the acid-derived part. For example, methyl ethanoate.
Esters are commonly used in artificial flavourings and fragrances due to their sweet, fruity smells.
Esters can be hydrolysed, that is, broken down by the addition of water, under acidic or alkaline conditions. Acid hydrolysis produces the original carboxylic acid and alcohol, while alkaline hydrolysis results in a carboxylate salt and alcohol.
The reaction of an alcohol with a carboxylic acid to produce an ester and water is known as esterification.

Amides are organic compounds that contain a carbonyl (C=O) group adjacent to an amine (N) group.
They are named by replacing the -oic acid or -ic acid ending of the parent carboxylic acid with -amide.
Amides can be hydrolysed under acidic or alkaline conditions to produce an amine and a carboxylic acid or carboxylate ion.
The conversion of an acyl chloride to an amide is commonly used in peptide synthesis, because the resulting compound can react with another amine to produce a peptide bond.