See image — Hydrocarbons Chemistry Question

💡 Solution & Explanation

Concept: Peracids (RCO3H) epoxidize alkenes via electrophilic epoxidation. The reaction is selective for the more electron-rich or more accessible double bond. Step 1 - Identify the starting material: The starting material is 1,2-dihydronaphthalene (or more precisely the structure shown appears to be a bicyclic compound with two six-membered rings fused together, with one double bond present in one of the rings - specifically it looks like octa-1(6),2-diene type or 1,2-dihydronaphthalene where one ring has a double bond). Step 2 - Identify the reagent: CH3-C(=O)-O-O-H is peracetic acid (a peracid), which is a classic reagent for epoxidation of alkenes (Prilezhaev reaction). It converts C=C to an epoxide in a concerted, syn-addition mechanism. Step 3 - Identify which double bond reacts: The starting material has one C=C double bond (in the partially unsaturated ring). Peracetic acid will epoxidize this double bond to give the corresponding epoxide. Step 4 - Determine the major product: The peracid epoxidizes the isolated double bond in the cyclohexene-type ring of the bicyclic system. This gives the epoxide shown in option (b), where the double bond of the unsaturated ring has been converted to an epoxide, and the rest of the ring system remains intact. The product retains the other unsaturated ring (with its double bonds) while the epoxide forms on the isolated alkene. Step 5 - Why not other options: - Option (a): Shows epoxidation at a different position (the saturated ring side), which is not where the double bond is located. - Option (c): A diol would require acid-catalyzed ring opening of an epoxide with water, which is not what peracid alone gives as the direct major product. - Option (d): Shows a different connectivity with OH groups at bridgehead positions, inconsistent with direct peracid epoxidation. The major product of peracetic acid reacting with the starting bicyclic alkene is the epoxide at the position of the double bond, corresponding to structure (b). Therefore, the correct answer is B.