See image — IUPAC and Nomenclature Chemistry Question

💡 Solution & Explanation

Concept: In IUPAC nomenclature, substituents are atoms or groups attached to the principal characteristic group (parent chain). The parent chain is chosen as the longest carbon chain containing the principal characteristic group (here, the carboxylic acid). Any group that branches off or replaces a hydrogen on the parent chain is counted as a substituent. Step 1: Identify the parent chain. The compound is: CH3-C(Cl)=CH-CHBr-CHI-COOH. The longest chain containing the -COOH group goes through: C1(COOH)-C2(I)-C3(Br)-C4=C5(Cl)-C6(CH3). Wait, let us re-examine. The structure from the image is: Cl and CH3 are on the same carbon of a double bond, then CH(Br), then CH(I), then COOH. So the chain is: HOOC-CHI-CHBr-CH=C(Cl)-CH3. The parent chain (longest chain with COOH) = 5 carbons if we count COOH carbon: C1(COOH), C2(I), C3(Br), C4=C5, with Cl on C5 and CH3 on C5. OR the parent chain could be 6 carbons including the methyl: C1(COOH)-C2(I)-C3(Br)-C4=C5(Cl)-C6H3 — but the methyl is part of the main chain making it a 6-carbon chain (hex-4-enoic acid framework) if taken linearly. Step 2: Determine the parent chain more carefully. The structure is: HOOC-CHI-CHBr-CH=C(Cl)-CH3. Reading as a straight chain: 6 carbons total (including COOH carbon and terminal CH3). Parent chain = hex-4-en-1-oic acid (or 2-iodo-3-bromo-5-chlorohex-4-enoic acid type structure). The methyl (CH3) at position 6 is part of the main chain. Step 3: Identify substituents on the parent chain. On C2: Iodo (I) — substituent 1. On C3: Bromo (Br) — substituent 2. On C5: Chloro (Cl) — substituent 3. The methyl group at C6 is the terminal carbon of the main chain, not a substituent. The OH of COOH is part of the principal characteristic group, not a substituent. Step 4: Count substituents. I, Br, Cl = 3 substituents total. Why other options fail: - (a) 1: Undercounts; there are clearly three halogens. - (b) 2: Undercounts by one halogen. - (d) 4: Would require counting the methyl or OH as a substituent, which are part of the main chain and principal group respectively. Therefore, the correct answer is C.