Question

The correct IUPAC name of

• A. 4-Ethyl-1-Fluoro-2-nitrobenzene
• B. 1-Ethyl-4-Fluoro-3-nitrobenzene
• C. 3-Ethyl-6-Fluoronitrobenzene
• D. 5-Ethyl-2-Fluoronitrobenzene

Answer 1

The Correct Option is A

To determine the correct IUPAC name for the given compound, we need to follow the IUPAC nomenclature rules for aromatic compounds such as substituted benzene derivatives.

1. Identify the parent hydrocarbon: Here, the base structure is a benzene ring.
2. Identify and prioritize the substituents according to the IUPAC rules:
   • The substituents on the benzene ring are ethyl, fluoro, and nitro groups.
   • Priority for numbering is given as per the alphabetical order of substituent names (ignoring prefixes like di-, tri-, etc.) when no higher order functional group is present. Here, 'E' for ethyl and 'F' for fluoro have priority over 'N' for nitro.
3. Number the benzene ring starting from the substituent with the highest priority:
   • The ethyl group will get the lowest position possible due to the alphabetical order rule (assuming it is at position 1), followed by the fluoro group (at position 4) and the nitro group (at position 2).
4. Write the complete IUPAC name with correct locants:
   • The IUPAC name becomes 4-Ethyl-1-Fluoro-2-nitrobenzene, addressing the positions of respective substituents on the benzene ring.

Therefore, the correct answer among the options is 4-Ethyl-1-Fluoro-2-nitrobenzene.

Other options are ruled out because they do not follow the correct numbering sequence as per IUPAC rules:

• 1-Ethyl-4-Fluoro-3-nitrobenzene: Incorrect position for the nitro group.
• 3-Ethyl-6-Fluoronitrobenzene: Does not follow the correct numbering for reducing complexity.
• 5-Ethyl-2-Fluoronitrobenzene: Incorrect positioning of substituents as per lowest sum rule.

Thus, by following the IUPAC nomenclature rules, the correct name for the compound is clearly established as 4-Ethyl-1-Fluoro-2-nitrobenzene.