See image — IUPAC and Nomenclature Chemistry Question

💡 Solution & Explanation

To match each compound with its IUPAC name, we must identify the ring type (cyclopropane vs. cyclopropene), locate the double bond, and number the carbons to give substituents the lowest possible locants. Key principles: - Cyclopropene has a double bond (3-membered ring with one double bond). The double bond carbons are C1 and C2; the sp3 carbon is C3. - Cyclopropane has no double bond (all sp3 carbons). - Numbering must give the lowest set of locants to substituents, with the double bond getting C1-C2 in cyclopropene. - In cyclopropene, the double bond is fixed at C1=C2, so substituents on the double bond carbons are at C1 or C2, and substituents on the saturated carbon are at C3. Analysis of each compound: (a) Structure: Cyclopropene ring (one double bond present, shown by the double line). Cl is on one of the double-bond carbons (top), Br is on the sp3 carbon (bottom-left). This is a cyclopropene with one halogen on a double-bond carbon and one on the sp3 carbon. Numbering: double bond = C1=C2, Cl is at C1 (or C2), Br is at C3. To minimize locants, Cl is at C1, Br at C3. Name: 3-bromo-1-chlorocyclopropene → matches (r). (b) Structure: Cyclopropene ring. Br is on one of the double-bond carbons (top), Cl is on the sp3 carbon (bottom-left). Numbering: Br at C1, Cl at C3. Name: 1-bromo-3-chlorocyclopropene → matches (s). (c) Structure: Cyclopropene ring with three substituents. Br at top (double-bond carbon), Cl at bottom-left (sp3 carbon), Br at bottom-right (the other double-bond carbon). So both double-bond carbons (C1 and C2) bear Br, and the sp3 carbon (C3) bears Cl. Name: 1,2-dibromo-3-chlorocyclopropene → matches (q). (d) Structure: Cyclopropane ring (no double bond shown; the lines indicate a cyclopropane). Cl at top carbon, Br at bottom-left carbon, Br at bottom-right carbon. This is a cyclopropane (saturated) with Cl at one carbon and Br at two other carbons. Numbering to give lowest locants: Cl at C2, Br at C1 and C3 → 1,3-dibromo-2-chlorocyclopropane → matches (p). Verification that other options fail: - (a) cannot be (p) because (a) has a double bond (cyclopropene), not cyclopropane. - (b) cannot be (r) because (r) is 3-bromo-1-chloro (Cl on double bond carbon), but (b) has Br on the double bond carbon. - (c) cannot be (s) because (c) has two Br atoms. - (d) cannot be (q) because (d) has no double bond. Therefore, the correct answer is {"a": "r", "b": "s", "c": "q", "d": "p"}.