See image — IUPAC and Nomenclature Chemistry Question

💡 Solution & Explanation

Step 1: Identify the parent chain/ring. The molecule is a cyclohexane ring bearing an -OH group, so the parent name is cyclohexanol. Step 2: Identify all substituents on the ring. From the structure: there is a hydroxyl (-OH) group, a bromine (Br) atom, a chlorine (Cl) atom, and an ethynyl group (-C≡CH). Step 3: Assign the principal characteristic group and numbering. The -OH group receives the lowest possible locant as the principal characteristic group in cyclohexanol nomenclature, so C1 = OH-bearing carbon. Step 4: Number the ring to give lowest locants to substituents. Starting from the OH carbon as C1 and numbering to give Br the next lowest locant: C1 (OH), C2 (Br), then continuing around the ring C3 (unsubstituted), C4 (Cl), C5 (ethynyl). Step 5: Verify the locant set. The set {1, 2, 4, 5} is achieved with this numbering. Numbering in the other direction would give {1, 6, 4, 3} = {1, 3, 4, 6}, which is higher at the second point of difference (3 vs 2), so the first numbering is correct. Step 6: Arrange substituents alphabetically. Bromo (2), chloro (4), ethynyl (5), then the parent cyclohexanol (1). Step 7: Compile the name: 2-bromo-4-chloro-5-ethynylcyclohexan-1-ol, commonly written as 2-bromo-4-chloro-5-ethynylcyclohexanol. Therefore, the correct answer is 2-bromo-4-chloro-5-ethynylcyclohexanol.