See image — Reaction Mechanism Chemistry Question

💡 Solution & Explanation

Concept: A 1,2-migration (shift) of an alkyl group from carbon to oxygen occurs when a carbon bearing an alkyl group migrates to an adjacent electrophilic oxygen center. Step 1 - Analyze option (a): Pinacol-pinacolone rearrangement involves migration of an alkyl (or aryl) group from carbon to an adjacent carbocation (carbon), i.e., C-to-C migration. The leaving group is water from a protonated diol, and the migrating group moves to the carbocation carbon, not to oxygen. So option (a) does NOT involve C-to-O migration. Step 2 - Analyze option (b): Baeyer-Villiger oxidation involves treatment of a ketone with a peracid. The mechanism proceeds via a Criegee intermediate where the alkyl group migrates from the carbonyl carbon to the adjacent peroxy oxygen (the 'O' of the O-O bond). This is a classic example of alkyl group migration from carbon to oxygen. So option (b) DOES involve C-to-O migration. Step 3 - Analyze option (c): Preparation of phenol from cumene hydroperoxide involves acid-catalyzed rearrangement of cumene hydroperoxide (PhC(CH3)2-O-OH). In the mechanism, the phenyl (or methyl) group migrates from the carbon to the adjacent oxygen of the protonated hydroperoxide, yielding a hemiketal-like intermediate that cleaves to give phenol and acetone. This is again a C-to-O migration. So option (c) DOES involve C-to-O migration. Step 4 - Conclusion: Both (b) and (d) involve migration of an alkyl/aryl group from carbon to oxygen, making option (d) 'Both (b) & (c)' the correct answer. Therefore, the correct answer is D.