Baeyer-Villiger oxidation is a peracid oxidation that converts ketones into esters and cyclic ketones into lactones. In Organic Chemistry II, it is a carbonyl rearrangement reaction with strong regioselectivity.
Baeyer-Villiger oxidation is a carbonyl oxidation in Organic Chemistry II that converts a ketone into an ester, or a cyclic ketone into a lactone, using a peracid such as MCPBA or peracetic acid. If the starting carbonyl is an aldehyde, the product is usually a carboxylic acid instead of an ester.
The part that makes this reaction memorable is that it does more than add oxygen. One atom from the peracid gets inserted next to the carbonyl, and one group attached to the ketone migrates during the rearrangement. So the carbon skeleton changes, not just the oxidation state.
Mechanistically, the peracid first reacts with the carbonyl oxygen to form a tetrahedral intermediate called the Criegee intermediate. Then one of the groups on the carbonyl carbon shifts over to oxygen as the leaving group departs. That migration step is the heart of the reaction, because it decides which alkyl group ends up next to the new oxygen.
This is why Baeyer-Villiger oxidation is so regioselective. When the two groups on the ketone are not the same, the group that migrates is usually the one better able to stabilize positive charge in the transition state. In many problems, that means tertiary or more substituted groups migrate more readily than methyl or primary groups.
Cyclic ketones are a common place to see it in this course. After oxidation, the ring expands by one atom and becomes a lactone. That makes the reaction useful in synthesis questions where you need to build a larger oxygen-containing ring from a smaller cyclic ketone.
The key idea to track is the before and after: a ketone becomes an ester-like product, and the reaction keeps the carbonyl framework but changes the connectivity. If you can spot a peracid and a ketone, especially a cyclic one, Baeyer-Villiger oxidation is usually the move to think about.
Baeyer-Villiger oxidation shows up in Organic Chemistry II because it is one of the cleanest examples of a carbonyl transformation that changes both oxidation level and molecular shape. You are not just memorizing another reagent, you are learning how chemists redesign a carbon skeleton without fully breaking it apart.
This reaction also connects several chapter ideas at once: carbonyl reactivity, oxidation-reduction logic, reaction mechanisms, and regioselectivity. If you can explain why one group migrates over another, you are practicing the same kind of reasoning used across carbonyl chemistry, especially when comparing related oxidations and rearrangements.
It is especially useful for synthesis problems. A professor may give you a cyclic ketone and ask for the product after MCPBA, or show you a lactone and ask you to work backward to the ketone precursor. Those are not trivia questions. They test whether you can recognize a functional group change and predict how the ring or chain will change shape.
It also helps with mechanism questions, because the Baeyer-Villiger pathway is a good example of a rearrangement driven by a better leaving arrangement and a favorable migration step. Once you understand this one, other oxidation and rearrangement problems feel less random.
Keep studying Organic Chemistry II Unit 3
Visual cheatsheet
view galleryPeracid
Baeyer-Villiger oxidation depends on a peracid as the oxidizing reagent. The peracid provides the oxygen that becomes part of the ester or lactone, and it also sets up the rearrangement through the Criegee intermediate. If you see MCPBA or peracetic acid in a problem, the reagent clue often points straight to this reaction.
Carbonyl Compound
The reaction starts with a ketone or aldehyde, so spotting the starting carbonyl is the first step. In synthesis problems, you look at whether the carbonyl is cyclic, which predicts lactone formation, or acyclic, which predicts an ester. The carbonyl is not just the site of attack, it is the place where migration changes the structure.
Oxidation-Reduction Reaction
Baeyer-Villiger oxidation fits the broader oxidation and reduction chapter because the carbonyl is being oxidized overall. At the same time, the product still keeps a carbonyl, so it can feel less dramatic than a full conversion to an alcohol or acid. That makes it a good example of why oxidation in organic chemistry is about bond changes, not just adding oxygen.
Jones Oxidation
Jones oxidation also uses strong oxidizing conditions, but it does something very different. Jones typically oxidizes alcohols to carbonyl compounds, while Baeyer-Villiger converts a ketone into an ester or lactone. Comparing them helps you separate simple oxidation from oxidation plus rearrangement.
A quiz question may give you a ketone plus MCPBA and ask for the product, so you need to identify the new ester or lactone and keep track of which group migrates. In problem sets, you may be asked to explain why one substituent moves instead of another, which means using regioselectivity and carbocation-like migration stability. Mechanism questions often want the peracid addition, the Criegee intermediate, and the rearrangement step in order. If a ring expands by one atom, Baeyer-Villiger oxidation is usually the reaction to name. On synthesis homework, you may also work backward from a lactone to the original cyclic ketone.
Both are oxidation reactions in carbonyl chemistry, but they do not make the same products. Jones oxidation usually turns alcohols into aldehydes, ketones, or carboxylic acids, while Baeyer-Villiger oxidation turns ketones into esters and cyclic ketones into lactones. If the reaction includes a peracid and a ketone, think Baeyer-Villiger. If it uses chromic acid conditions on an alcohol, think Jones.
Baeyer-Villiger oxidation converts a ketone into an ester, and a cyclic ketone into a lactone, using a peracid.
The reaction is more than a simple oxidation because one substituent migrates during the rearrangement.
Regioselectivity matters, since the group that migrates is usually the one that can best stabilize the transition state.
The reaction is especially useful in synthesis problems because it can expand a ring by one atom.
If you see MCPBA or peracetic acid next to a ketone, Baeyer-Villiger oxidation is a strong possibility.
It is a peracid oxidation that converts ketones into esters and cyclic ketones into lactones. The reaction also involves a rearrangement, so one group on the carbonyl carbon migrates as the oxygen is inserted.
Acyclic ketones usually become esters, and cyclic ketones become lactones. Aldehydes can also react, but they usually give carboxylic acids instead of esters.
Because one group migrates during the rearrangement step, and not all groups migrate equally well. The group that can better stabilize the developing positive character usually wins, so the product is often predictable from the ketone structure.
Look for a ketone plus a peracid like MCPBA or peracetic acid. If the product has one extra oxygen next to the carbonyl, or a ring has expanded to a lactone, that is a strong clue you are looking at this reaction.