Baeyer-Villiger Oxidation: Mechanism
The reaction is initiated by addition of peracid to the ketone. The addition is catalyzed by protons originating from the peracid or the carboxylic acid formed during the reaction.
At the same time, the peracid functions as a nucleophile by attacking the carbonyl carbon with the terminal oxygen atom, thereby forming an α-hydroxyperoxy ester.
Contrary to the behavior of peracids and simple hydroperoxides, hydroxyperoxy esters spontaneously decompose already at room temperature. 1,2-Migration of the the substituents R' or R" produces an ester and a carboxylic acid derived from the peracid.
Migration of the substituent takes place with retention, i.e. a pure enantiomeric ketone produces a pure enantiomeric ester.