In the IUPAC system, aliphatic carboxylic acids are named by replacing the ending –e in the name of the corresponding alkane with –oic acid. In numbering the carbon chain, the carboxylic carbon is numbered one. For naming compounds containing more than one carboxyl group, the alkyl chain leaving carboxyl groups is numbered and the number of carboxyl groups is indicated by adding the multiplicative prefix, dicarboxylic acid, tricarboxylic acid, etc. to the name of parent alkyl chain. The position of –COOH groups are indicated by the arabic numeral before the multiplicative prefix.

What is the IUPAC name of the given compound?

3,3-Dimethylbutanoic acid

The correct answer is option 3. 3,3-Dimethylbutanoic acid

The longest parent carbon chain consists of 4 carbon atoms including the carboxyl carbon and one methyl group attached to the tertiary carbon. The other two methyl groups act as substituents on the carbon, which is now the third carbon.