Organic Chemistry: Carboxylic Acids

Carboxylic acids are part of a homologous series in organic chemistry. They have a functional group of -COOH.
This class of compounds can be identified by their acidic properties because carboxylic acids can donate a proton (H+) in a solution.
Chemically, carboxylic acids display properties of both alcohols and alkenes due to the presence of hydroxyl -OH and carbonyl C=O groups respectively.
The ‘-OH’ in the functional group can form hydrogen bonds with water, which makes carboxylic acids soluble in water. However, this solubility decreases with increasing carbon chain length.

In the nomenclature of carboxylic acids, the suffix ‘-anoic acid’ is added to the stem name of the corresponding alkane.
For instance, CH3COOH is called ethanoic acid reflecting the two carbon atoms in the molecule.
Other examples include propanoic acid (C3H6O2) and butanoic acid (C4H8O2).
When multiple carboxylic groups are present the prefix di, tri, etc are used.

Carboxylic acids can undergo a variety of reactions due to their dual reactivity of alcohol and alkenes.
Primary reactions include esterification (reaction with alcohol to produce esters), formation of acid chlorides and amides (reaction with thionyl chloride or amines) and neutralisation (reaction with bases).
They also react with carbonates and hydrogencarbonates to release carbon dioxide.

Carboxylic acids are known for their diverse applications. Smaller carboxylic acids are often used in food and beverages as they are component of vinegar (ethanoic acid).
Some are used in the manufacturing of soaps and detergents as they can react with alkalis to form salts.
Larger carboxylic acids are widely used in the production of plastics and polymers, such as the formation of polyesters.
Understanding the chemical properties of carboxylic acids can help in predicting the behaviour of larger organic molecules.