Question

The IUPAC name of
(A) $4 - {\text{hydroxy - }}2 - {\text{methyl}}\;{\text{pentanal}}$
(B) $2 - {\text{hydroxy - 4}} - {\text{methyl}}\;{\text{pentanal}}$
(C) $4 - {\text{hydroxy - }}2 - {\text{methyl}}\;{\text{pentanol}}$
(D) $2 - {\text{hydroxy - 4}} - {\text{methyl}}\;{\text{pentanol}}$

Answer 1

The IUPAC stands for the International Union of Pure and Applied Chemistry. The IUPAC name is given to the compound based on some rules and priority order of the functional group. The process of naming the compounds is known as the nomenclature.

Complete step by step answer:
To find or predict the IUPAC name of the given compound we should know some basic rules of nomenclature of an organic compound. So we will follow the rules step by step to predict the correct IUPAC name of the given compound. So, first, we will identify the parent chain of the given compound which is the chain with the maximum number of carbon atoms. So from the compound, we can observe that the parent chain will be the straight-chain with five carbon atoms and two functional groups. The functional groups are alcohol $- OH$ and aldehyde $- CHO$ . Now we will do the numbering over the parent chain carbon atoms which can be either from the right or left. So, according to the priority order of functional groups, the aldehyde group $- CHO$ will be preferred over alcohol. So, the functional group aldehyde $- CHO$ will be the reference. So, the numbering will be as given below.

So, after the numbering we can observe that methyl is at position $2$ and alcohol is at $4$ . Hence, the IUPAC name is $4 - {\text{hydroxy - }}2 - {\text{methyl}}\;{\text{pentanal}}$ .
Therefore, the correct option is (A).

Note:
If there is a substituent which is a functional group-containing carbon atom will be included in the parent chain. If there are two-parent chains that have the same number of carbon atoms then the chain with more number of side chains or substituents will be considered as the parent chain.