Question

Write $IUPAC$ the name of the following compound:

A. $2 -$amino$- 4 -$hydroxybenzoic acid
B. $6 -$amino$- 4 -$hydroxybenzoic acid
C. $3 -$amino$- 4 -$carboxyphenol
D. $2 -$carboxy$- 4 -$hydroxyaniline

Answer 1

The $IUPAC$ system of nomenclature involves the naming according to the priority functional groups present in the molecule. The numbering is given in the system mentioning each functional group present on the molecule. One can develop an approach to the question by analyzing functional groups and numbering in the given structure.

Complete step by step answer:
-First of all, we will see the total functional groups present in the given structure, which are the amino group which shows the chemical formula $- N{H_2}$ in the structure. The hydroxyl functional group is present which shows the chemical formula as $- OH$ in the structure. The carboxylic functional group is present which shows the chemical formula as $- COOH$ in the structure.
-Now we are going to see how to give priority to the functional groups in the structure. The first priority is given to the functional group in the structure which has the highest molecular weight amongst all the functional groups present in the structure. Hence, the numbering will start from the group $- COOH$ which is marked as the number $1$ and this functional group is named in the longest chain of the molecule as it forms the longest chain, which in this case is benzoic acid where benzene ring is attached to carboxylic acid.
-Then the numbering begins from the carboxylic group and it proceeds from that side which has attached functional group nearest to the first priority group. Hence, the amino group will get the number $2$
- At the number $4$ position, there is the presence of the hydroxyl group. Refer the diagram for a better understanding of numbering,
-Hence, the $IUPAC$ name of the structure is $2 -$amino$- 4 -$hydroxybenzoic acid which shows option A as a correct choice.

Note: The functional group which forms the longest chain in the molecule is named as the basic structure in the molecule. It is important to give further numbering to the carbon chain which has a functional group attached nearer to the main functional group which has given the number one priority in the structure.