Question

The IUPAC name of the following compound is:
${{H}_{3}}C-CH(C{{H}_{3}})-CH(OH)-C{{H}_{2}}-COOH$
(A)- 2-Methyl-3-hydroxypentan-5-oic acid
(B)- 4,4-Dimethyl-3-hydroxy butanoic acid
(C)- 3-Hydroxy-4-methylpentanoic acid
(D)- 4-Methyl-3-hydroxypentanoic acid

Answer 1

In the IUPAC naming, the priority of the functional group is considered to identify the main functional group of the compound. This is followed by the length of the parent chain with respect to the main functional group. Then, the position of the remaining substituents is allotted.

Complete step by step answer:
-In the given compound, there are two functional groups, that is alcohol and carboxylic acid. In the carbon-containing functional group, the group in which the central atom has higher oxidation state is prioritised. Thus, the carboxylic acid is preferred over the alcohol group.
-So, in the given compound, the carboxylic acid group being highest in the priority, forms the main functional group in the identification and the alcohol acts as the substituent. The length of the carbon-chain with respect to the carboxylic group is determined such that the longest chain is chosen including the carboxyl group. So, we have, five-membered carbon chain, where the suffix (-ane) of pentane is replaced by (-anoic acid) of pentanoic acid. The numbering of the pentanoic acid carbon chain is done in such a manner that the substituents attached acquire the lowest number. Thus, the hydroxyl and methyl substituent are numbered 3 and 4 respectively.

Therefore, we get the IUPAC name of the given compound to be option (C)- 3-Hydroxy-4-methylpentanoic acid.

Note: In the naming, the position of the carboxylic acid group is not mentioned as it is at the extreme end at C-1 position of the parent chain. The IUPAC naming is done as prefix of substituents + word root of parent chain + primary suffix + secondary suffix of functional group.