aryl rings' migratory aptitudes can explain this. Hydroxyl groups ortho or para to the carbonyl group concentrate electron density at the aryl carbon bonded to the carbonyl carbon (10c, 11d). Phenyl groups have low migratory aptitude, but higher electron density at the migrating carbon increases migratory aptitude, facilitating [1,2]-aryl migration and allowing the reaction to continue. M-hydroxy compounds do not concentrate electron density at the migrating carbon (12a, 12b, 12c, 12d); their aryl groups' migratory aptitude remains low. The benzylic hydrogen, which has the highest migratory aptitude, migrates instead (8), forming a phenyl carboxylic acid (9). Other functional groups on the aryl ring Substitution of phenyl hydrogens with electron-donating groups ortho or para to the carbonyl group increases electron density at the migrating carbon, promotes [1,2]-aryl migration, and accelerates oxidation. Substitution with electron-donating groups meta to the carbonyl group does not change electron density at the migrating carbon; because unsubstituted phenyl group migratory aptitude is low, hydrogen migration dominates. Substitution with electron-withdrawing groups ortho or para to the carbonyl decreases electron density at the migrating carbon (13c), inhibits [1,2]-aryl migration, and favors hydrogen migration. pH The hydroperoxide anion is a more reactive nucleophile than neutral hydrogen peroxide. Consequently, oxidation accelerates as pH increases toward the pKa of hydrogen peroxide and hydroperoxide concentration climbs. At pH higher than 13.5, however, oxidation does not occur, possibly due to deprotonation of the second peroxidic oxygen. Deprotonation of the second peroxidic oxygen would prevent [1,2]-aryl migration because the lone oxide anion is too basic to be eliminated (2). Deprotonation of the hydroxyl group increases electron donation from the hydroxyl oxygen. When the hydroxyl group is ortho or para to the carbonyl group, deprotonation increases the electron density at the migrating carbon, promoting faster [1,2]-aryl migration. Therefore, [1,2]-aryl migration is facilitated by the pH range that favors deprotonated over protonated hydroxyl group. Variants Acid-catalyzed Dakin oxidation The Dakin oxidation can occur in mild acidic conditions as well, with a mechanism analogous to the base-catalyzed mechanism. In methanol, hydrogen peroxide, and catalytic sulfuric acid, the carbonyl oxygen is protonated (14), after which hydrogen peroxide adds as a nucleophile to the carbonyl carbon, forming a tetrahedral intermediate (15). Following an intramolecular proton transfer (16,17), the tetrahedral intermediate collapses, [1,2]-aryl migration occurs, and water is eliminated (18). Nucleophilic addition of methanol to the carbonyl carbon forms another tetrahedral intermediate (19). Following a second intramolecular proton transfer (20,21), the