Question

The IUPAC name of the following molecule is

• A. 2 - Methyl - 5 nitro - 1 - chlorobenzene
• B. 3 - Chloro - 4 methyl - 1 - nitrobenzene
• C. 2 - Chloro - 1 methyl - 4 - nitrobenzene
• D. 2 - Chloro - 4 nitro - 1 - methylbenzene

Hint:

When naming substituted benzene rings, prioritize numbering to give the lowest set of locants to the substituents. If multiple numbering schemes give the same lowest set, then alphabetize the substituents to determine the correct order.

Answer 1

The Correct Option is C

Step 1: Identify the parent chain.
The parent chain is benzene.
Step 2: Number the benzene ring to give the lowest locants to the substituents, prioritizing alphabetical order.
Substituents are chloro (-Cl), methyl (-CH$_3$), and nitro (-NO$_2$). Alphabetical order: chloro, methyl, nitro.
Assign position 1 to the carbon with chloro. Numbering clockwise gives methyl at 2 and nitro at 4 (1, 2, 4). Numbering counterclockwise gives methyl at 6 and nitro at 3 (1, 3, 6). The lowest set is 1, 2, 4.
Step 3: Name the substituents with their positions.
Chloro at position 2
Methyl at position 1
Nitro at position 4
Step 4: Write the IUPAC name in alphabetical order of substituents followed by benzene.
2-chloro-1-methyl-4-nitrobenzene
Thus, the IUPAC name is $ \boxed{2 - Chloro - 1 methyl - 4 - nitrobenzene} $.