See image — IUPAC and Nomenclature Chemistry Question

💡 Solution & Explanation

Step 1: Identify the parent chain. The compound contains a benzene ring, so the parent name is 'benzene' with the suffix for the principal characteristic group. The sulphonic acid group (-SO3H) is the principal characteristic group, giving the suffix '-sulphonic acid', so the parent name becomes 'benzenesulphonic acid'. Step 2: Identify all substituents on the ring. From the structure: a sulphonic acid group (-SO3H) at one carbon, a nitro group (-NO2) on an adjacent carbon (ortho), and a methyl group (-CH3) on the carbon adjacent to the nitro group (which is two positions away from -SO3H). Step 3: Number the ring to give the lowest locants to substituents, with the principal characteristic group (-SO3H) at C1. Going around the ring: C1 = -SO3H, C2 = H, C3 = -NO2, C4 = -CH3. This gives locants 3 and 4 for nitro and methyl respectively. Step 4: Assign substituent names with locants. The methyl group at C4 is '4-methyl', and the nitro group at C3 is '3-nitro'. Step 5: Assemble the IUPAC name. Substituents are listed alphabetically: methyl (m) before nitro (n), giving '4-methyl-3-nitro'. The full name is 4-Methyl-3-nitrobenzene sulphonic acid. Step 6: Verify. The structure shows -SO3H at C1, -NO2 at C3 (meta to -SO3H), and -CH3 at C4 (para to -SO3H, ortho to -NO2), consistent with the name. Therefore, the correct answer is 4-Methyl-3-nitrobenzene sulphonic acid.