Explain the following terms:
$(a)$ Carboxylic acid and carboxyl group
$(b)$ Aliphatic and aromatic carboxylic acids
$(c)$ Fatty acids

(N/A) Carboxylic acid and carboxyl group:
$(i)$ Compounds that contain a carboxyl group $(-COOH)$ as a functional group are known as carboxylic acids.
$(ii)$ In a carboxyl group,a carbonyl group $(C=O)$ is attached to a hydroxyl group $(-OH)$. The name 'carboxyl' is derived from 'carbonyl' and 'hydroxyl'.
$(iii)$ The carboxyl group contains both a carbonyl group and a hydroxyl group.
$(b)$ Aliphatic and aromatic carboxylic acids:
| Aliphatic carboxylic acid | Aromatic carboxylic acid |
| :--- | :--- |
| $R-COOH$ | $Ar-COOH$ |
| The carboxyl carbon is attached to an alkyl group. | The carboxyl carbon is attached to an aryl group. |
| e.g.,$CH_3COOH$ | e.g.,$C_6H_5COOH$ |
$(c)$ Fatty acids: Naturally occurring aliphatic carboxylic acids with long carbon chains (typically $C_{12}$ to $C_{18}$) are known as fatty acids. They are often found as esters of glycerol in natural fats and oils.