How are carboxylic acids named using IUPAC rules?

Carboxylic acids are named in the IUPAC system by following a few simple rules.

Steps for Naming:

1. Identify the longest carbon chain that contains the carboxyl group.
2. Replace the final “-e” of the corresponding alkane name with “-oic acid”.
   • Example: methane → methanoic acid.
3. Number the chain so that the carboxyl carbon is always carbon 1 (no need to mention its position in the name, since it’s always at the end).
4. Name and number substituents (like methyl, bromo, chloro, etc.) and add them as prefixes.
5. For aromatic acids (when the carboxyl group is attached directly to a benzene ring), the base name is benzoic acid.

Examples:

• HCOOH → methanoic acid (common name: formic acid).
• CH₃COOH → ethanoic acid (common name: acetic acid).
• CH₃CH₂CH₂COOH → butanoic acid.
• C₆H₅COOH → benzoic acid.
• 2-methylpropanoic acid → a three-carbon chain with a methyl group on the second carbon.

In short: Longest chain + “oic acid” ending + substituents as prefixes.