See image — Hydrocarbons Chemistry Question

💡 Solution & Explanation

Step 1 - Identify the starting material: The starting material is 2-(hydroxymethyl)tetrahydrofuran, a THF ring bearing a -CH2OH group at C2. Step 2 - First reaction (H+/Delta -> A): Under acid and heat, the primary alcohol (-CH2OH) is protonated and the molecule undergoes an intramolecular ring-opening/ring-expansion. The oxygen of the THF ring acts as a nucleophile or the hydroxyl acts as a leaving group; the five-membered ring opens to give a carbocation or oxocarbenium intermediate, which then recyclizes. Specifically, protonation of the hydroxyl gives a primary carbocation-like species; the ring oxygen attacks in an SN1 fashion, opening the THF and closing a six-membered ring. This ring-expansion converts the five-membered cyclic ether (THF derivative) into dihydropyran or an oxocarbenium ion intermediate (tetrahydropyranyl cation at C1, i.e., an oxocarbenium ion). The product A is 3,4-dihydro-2H-pyran (DHP) formed by elimination, or more precisely a tetrahydropyranyl cation. Step 3 - Second reaction (ROH/H+ -> B major): The intermediate A (dihydropyran or the cyclic oxocarbenium ion) reacts with ROH under acid catalysis. Dihydropyran (3,4-dihydro-2H-pyran) reacts with an alcohol ROH under acid catalysis to give 2-alkoxytetrahydropyran as the major product. This is electrophilic addition of ROH across the enol ether double bond: the proton adds to C3 (Markovnikov, since C2 is stabilized as oxocarbenium), and RO- adds to C2, giving 2-OR-tetrahydropyran. Step 4 - Why other options fail: (a) 3-OR-tetrahydropyran would require anti-Markovnikov addition, which is not favored under acid catalysis. (c) This would be the starting enol ether (DHP + OR), not the addition product. (d) A peroxy linkage is not formed under these conditions. Step 5 - Conclusion: The major product B is 2-alkoxytetrahydropyran (tetrahydropyran with OR at C2), which corresponds to option (b). Therefore, the correct answer is B.