Química Orgánica 2 · Herramientas de oxidación y reducción
Baeyer–Villiger oxidation of acetophenone to phenyl acetate
Condiciones: mCPBA, CH2Cl2, 25 °C
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Arrastra desde los electrones que se mueven hasta donde van, o toca uno y luego el otro. Cada flecha se revisa; Pista te ayuda cuando te atascas. No necesitas cuenta.
El mecanismo, paso a paso
Siguiente reproduce las flechas curvas de cada paso y las explica. Los pasos escritos están abajo.
Leer los 6 pasos escritos
mCPBA protonates the ketone
The peroxy acid O–H is acidic; the ketone oxygen takes that proton, making the carbonyl carbon strongly electrophilic and generating the peroxycarboxylate nucleophile.
Las flechas curvas
- A carbonyl oxygen lone pair takes the peroxy acid proton.
- The O–H pair stays on the peroxy oxygen.
The peroxy anion adds: the Criegee intermediate
The terminal peroxy oxygen attacks the protonated carbonyl carbon and the C=O π pair moves onto oxygen, giving the tetrahedral Criegee intermediate.
Las flechas curvas
- The peroxy anion lone pair forms a C–O bond to the carbonyl carbon.
- The C=O π pair moves onto the protonated oxygen, neutralising it.
Phenyl migrates to oxygen
In one concerted step the OH lone pair starts to re-form C=O, the phenyl group shifts with its bonding pair from carbon to the near peroxide oxygen, and the weak O–O bond breaks so 3-chlorobenzoate leaves.
Las flechas curvas
- An OH lone pair forms the C=O π bond.
- The phenyl group moves with its bond pair onto the peroxide oxygen.
- The O–O bond breaks and the carboxylate leaves.
Which group migrates?
Migration places partial positive charge on the moving group, so groups that stabilise positive charge move best.
Carboxylate removes the proton
3-Chlorobenzoate takes the proton from the protonated ester carbonyl, giving neutral phenyl acetate and 3-chlorobenzoic acid.
Las flechas curvas
- A carboxylate lone pair takes the proton.
- The O–H pair stays on the carbonyl oxygen.
Phenyl acetate
An oxygen atom has been inserted between the carbonyl carbon and the ring: acetophenone has become the ester phenyl acetate, and mCPBA has become 3-chlorobenzoic acid.
Qué vas a practicar
Draw protonation of acetophenone by mCPBA, addition of the peroxy anion to give the Criegee intermediate, migration of the phenyl group to oxygen with loss of 3-chlorobenzoate, and the final deprotonation to phenyl acetate.
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