See image — Alcohols Phenols and Ethers Chemistry Question

💡 Solution & Explanation

Concept: Migratory aptitude in 1,2-shifts (such as in pinacol rearrangement, Baeyer-Villiger oxidation, or Wolff rearrangement) depends on the ability of the migrating group to stabilize the partial positive charge at the migration terminus through electron donation. For aryl groups, electron-donating substituents increase migratory aptitude and electron-withdrawing substituents decrease it. Step 1: Identify the electronic nature of each substituent on the para-substituted aryl groups: - (a) para-OMe (methoxy): strong electron-donating group (EDG) by resonance → greatly increases electron density on ring → highest migratory aptitude - (d) para-Me (methyl): weak electron-donating group (EDG) by hyperconjugation/induction → moderately increases electron density → second highest - (b) unsubstituted phenyl: no substituent → baseline migratory aptitude → third - (c) para-Cl (chloro): electron-withdrawing group (EWG) by induction (net EWG despite lone pair donation) → decreases electron density → lowest migratory aptitude Step 2: Rank in decreasing order of migratory aptitude: 4-MeO-C6H4 (a) > 4-Me-C6H4 (d) > C6H5 (b) > 4-Cl-C6H4 (c) This gives: a > d > b > c Step 3: Match with options: Option (b) states a > d > b > c — this matches exactly. Why other options fail: - Option (a) a > c > b > d: places Cl above unsubstituted phenyl and methyl, which is incorrect since Cl is EWG. - Option (c) a > d > c > b: places Cl above unsubstituted phenyl, incorrect. - Option (d) b > c > a > b: nonsensical and places EWG Cl above EDG OMe. Therefore, the correct answer is B.