IUPAC and NomenclaturemediumSUBJECTIVE

See imageIUPAC and Nomenclature Chemistry Question

Question

See image

Chemistry diagram for: See image
Answer: 2-BROMO-5-CHLOROCYCLOPENTA-2,4-DIEN-1-OL

💡 Solution & Explanation

Step 1: Identify the parent ring. The structure is a five-membered carbocyclic ring (cyclopentane base), making it a cyclopentane derivative. Step 2: Identify the degree of unsaturation within the ring. There are two double bonds visible in the ring (between C2-C3 and C4-C5), making the parent chain cyclopenta-2,4-diene. Step 3: Identify all substituents. There is a hydroxyl group (-OH), a bromine atom (-Br), and a chlorine atom (-Cl) attached to the ring. Step 4: Assign numbering to give lowest locants to substituents. The carbon bearing the -OH group is assigned C1 (as -ol suffix). The carbon bearing -Br is adjacent to C1, and with the double bonds at C2-C3 and C4-C5, -Br is at C2. The carbon bearing -Cl is on the other side of C1; with the numbering going so that the double bonds get locants 2 and 4, -Cl falls at C5. Step 5: Verify the numbering. Going around the ring: C1 (OH), C2 (Br, part of C2=C3 double bond), C3, C4 (part of C4=C5 double bond), C5 (Cl). This gives double bonds at positions 2,4 and substituents at 1 (OH), 2 (Br), 5 (Cl) — consistent with lowest locant set. Step 6: Construct the IUPAC name. Parent: cyclopenta-2,4-dien-1-ol (cyclopentadienol with OH at C1). Add substituents alphabetically as prefixes: 2-bromo and 5-chloro. Full name: 2-bromo-5-chlorocyclopenta-2,4-dien-1-ol. No other options are present to eliminate, but alternative numbering (e.g., placing Cl at C2 and Br at C5) would give 5-bromo-2-chlorocyclopenta-2,4-dien-1-ol, which has a higher locant set {2,5} vs {2,5} — same set, so alphabetical order of substituents dictates bromo before chloro, confirming Br at C2. Therefore, the correct answer is 2-bromo-5-chlorocyclopenta-2,4-dien-1-ol.

💬
Still have doubts about this question?
Send it to our AI chemistry tutor on WhatsApp — gets answered in minutes
Ask on WhatsApp →

Practice 22,000+ questions like this

AI-adaptive practice, video lectures, and full JEE Mains Chemistry content — all in one place.

JEE Advanced · JEE Mains · NEET · IChO · AP Chemistry