Rule 1 :- The longest chain in the molecule will be the parent chain. So, the first thing one should do is to find the longest carbon chain in the molecule.
Rule 2 :- Find out all the substituents present on the carbon chain. It can be any- from methyl to any alcohol substituent.
Rule 3 :- Start numbering the parent chain from the end such that the substituent gets the lowest number. This is called the lowest locant rule.
Rule 4 :- If the substituent occurs more than one time, then the prefix di, tri or tetra is being used with the location of the carbon on which it is present.
Rule 5 :- If more than one substituents are present and they are different. So, these will be named in alphabetical order.
In the given compound, Br is present at position 2and3, phenyl at position 1, parent chain has 5 carbon atoms.




