Question #de793
1 Answer
The hydrogen ion comes from the peroxyacid that is used as the oxidizing agent.
The Baeyer-Villiger reaction is the oxidation of a ketone to a carboxylic acid ester using a peroxyacid as the oxidizing agent. For example,
Commonly used peroxyacids are peroxyacetic acid, MCPBA , and peroxytrifluoroaceticacid with disodium hydrogen phosphate added as a buffer.
MECHANISM
The mechanism is complicated and takes place in several steps.
Step 1
The peroxyacid protonates the oxygen of the carbonyl group.
This makes the carbonyl carbon more electrophilic.
Step 2.
The peroxyacid anion attacks the carbonyl carbon to form a so-called Criegee intermediate.
Step 3.
The Criegee intermediate decomposes. As a carboxylate ion leaves, an alkyl group migrates to the adjacent O atom.
Step 4.
Finally, the carboxylate ion deprotonates the cation to produce the ester and a carboxylic acid.
