Question

The IUPAC name of the above compound is(are):

A. 1-chloro-4-methyl benzene
B. 1-methyl-4-chlorobenzene
C. 4-chlorotoluene
D. 4-methyl chlorobenzene

Answer 1

Hint: Certain rules are set for naming the substituted hydrocarbon chain which are set by IUPAC. Longest hydrocarbon chain is selected as the main chain and other carbons or substitutions are referred to as side chains and less important comparatively.

Complete step by step answer
Other than alkanes, alkenes and alkynes, there are functional groups as well. The functional groups are halides, alcohols, ketones, aldehydes and carboxylic acids, they affect the nomenclature by changing the suffix for alkane hydrocarbon chain.
Naming substituted cycloalkanes is straightforward: we name them as alkyl cycloalkanes, halo cycloalkanes, alkyl cycloalkanes, and so on. If only one substituent is present, it is not necessary to designate its position. Since this compound has two substituents therefore we number the ring beginning with the substituent first in alphabet and the number in the direction that gives the next substituent the lower number possible.
Functional groups have a certain priority order depending upon seniority during nomenclature. Since in the question we are given with alkyl and halide as functional groups, therefore let us discuss the prefix that each of them would give to the aromatic ring benzene.
A six carbon ring chain with resonance between its three double bonds is benzene. Now let us find the seniority among both the functional groups present which are methyl and chloride. Since chlorine has higher priority then it will be the position from where the numbering starts from.

Hence the correct option is A and D as they mean the same thing.

Note:
There are certain common names that are given for substituted benzenes, be it substituted with different functional groups. For example a benzene substituted with methyl is commonly called toluene.