Question

The correct IUPAC name

• A. 2-chloro-4-nitrotoluene
• B. 4-chloro-2-nitrotoluene
• C. 1-chloro-3-nitro-5-methylbenzene
• D. 3-chloro-5-nitrotoluene

Answer 1

Answer: (A)

2-chloro-4-nitrotoluene

Answer 2

The given compound is a substituted benzene. According to IUPAC nomenclature rules for substituted benzenes, if one of the substituents is part of an accepted common name for a benzene derivative, that name is preferred as the parent. Methylbenzene is commonly known as toluene and is an accepted IUPAC name. Therefore, toluene is the preferred parent name here, with the methyl group assigned position 1.

The substituents are a chlorine atom ($-\text{Cl}$) and a nitro group ($-\text{NO}_2$). If the methyl group is at position 1, the chlorine atom is at position 2, and the nitro group is at position 4.

The substituents other than the methyl group are chloro and nitro. In alphabetical order, 'chloro' comes before 'nitro'.

Thus, the correct IUPAC name is constructed by combining the locants and the names of the substituents in alphabetical order, followed by the parent name: 2-chloro-4-nitrotoluene.