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phenols: claisen rearragement

phenols: claisen rearragement. Structure and Nomenclature of Phenols Phenols have hydroxyl groups bonded directly to a benzene ring Naphthols and phenanthrols have a hydroxyl group bonded to a polycyclic benzenoid ring. The Claisen Rearrangement

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phenols: claisen rearragement

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  1. phenols:claisenrearragement

  2. Structure and Nomenclature of Phenols • Phenols have hydroxyl groups bonded directly to a benzene ring • Naphthols and phenanthrols have a hydroxyl group bonded to a polycyclic benzenoid ring Chapter 21

  3. The Claisen Rearrangement • Allyl phenyl ethers undergo a rearrangement upon heating that yields an allyl phenol • The process is intramolecular; the allyl group migrates to the aromatic ring as the ether functional group becomes a ketone • The unstable keto intermediate undergoes keto-enoltautomerization to give the phenol group • The reaction is concerted, i.e., bond making and bonding breaking occur at the same time

  4. Allyl vinyl ethers also undergo Claisen rearrangement when heated • The product is a g-unsaturated carbonyl compound • The Cope rearrangement is a similar reaction • Both the Claisen and Cope rearrangements involve reactants that have two double bonds separated by three single bonds

  5. The transition state for the Claisen and Cope rearrangements involves a cycle of six orbitals and six electrons, suggesting aromatic character • This type of reaction is called pericyclic • The Diels-Alder reaction is another example of a pericyclic reaction

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