JEE Main Chemistry question

A 2-methyl-substituted six-membered cyclic ether (2-methyltetrahydropyran-type ring, with a methyl group on the ring carbon adjacent to the ring oxygen) is treated with one equivalent of HI and heated. The principal organic product is

(A)The ring-opened iodo-alcohol, in which iodide has displaced the ring oxygen at the more hindered, methyl-bearing (secondary) ring carbon, while a hydroxyl group remains on the less hindered carbonCorrect
(B)The ring-retained product in which the ring oxygen is unaffected and only the methyl substituent is iodinated
(C)The ring-retained product with iodine substituted at a different, non-adjacent ring position
(D)A fully ring-opened product with iodine at both former ring-oxygen-attached carbons

Answer: (A)

Solution

With only one equivalent of HI, the protonated ring oxygen is opened preferentially at the more substituted, methyl-bearing ring carbon, since the developing positive character there is better stabilised (a more SN1-like pathway) than at the less hindered carbon; iodide ion

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Question ID VK-148796