Explain the nomenclature of carboxylic acids with suitable examples.

(N/A) Common names:
$(a)$ Carboxylic acid compounds were first obtained from nature,hence most of the acid compounds are known by their common names. In common nomenclature of acids,the suffix 'ic acid' is used,which is based on the natural source of the acid.
$(i)$ Formic acid is first obtained from red ant (formica).
$(ii)$ Acetic acid is obtained from vinegar.
$(iii)$ Butyric acid is obtained from rancid butter.
$(b)$ Often,substituted groups are indicated by $\alpha, \beta, \gamma \ldots$ starting from the carbon atom adjacent to the $-COOH$ group.
e.g.,$^{\beta} CH_{3} - ^{\alpha} CH(OH) - COOH$
$(B)$ $IUPAC$ nomenclature of aliphatic acids:
$(a)$ For naming aliphatic carboxylic acids,the suffix 'oic acid' is added by replacing the 'e' of the corresponding alkane.
$(i)$ $HCOOH$ is named methanoic acid.
$(ii)$ $CH_{3}COOH$ is named ethanoic acid.
$(b)$ In the carbon chain,the carbon atom of the carboxylic acid group is assigned the number $1$.
$(c)$ If more than one $-COOH$ group is present,the prefixes di-,tri-,etc.,are used before 'oic acid',and the 'e' of the alkane is not removed.
$(i)$ $HOOC-COOH$: Ethanedioic acid
$(ii)$ $HOOC-CH_{2}-CH_{2}-COOH$: Butanedioic acid
Examples of $IUPAC$ nomenclature:
| Structure | $IUPAC$ name |
| :--- | :--- |
| $(i) \ CH_{3}-CH(CH_{3})-CH_{2}-COOH$ | $3$-methylbutanoic acid |
| $(ii) \ CH_{3}-CH(Cl)-COOH$ | $2$-chloropropanoic acid |
| $(iii) \ CH_{3}-CH(OH)-COOH$ | $2$-hydroxypropanoic acid |
| $(iv) \ CH_{3}-CO-CH_{2}-CH_{2}-COOH$ | $4$-oxopentanoic acid |