Reactions of Aryl Ethers

Chapter 24: Phenols

Electrophilic Aromatic Substitution

electrophilic aromatic substitution of aryl ethers
Reaction type: Electrophilic Aromatic Substitution

Summary


Related reactions

Cleavage of Aryl Ethers by HI or HBr

acid cleavage of aryl ethers

Reaction type: Nucleophilic Substitution

Summary

Question:
Why don't phenols react with HBr to give aryl bromides ? the S<sub>N</sub>1 or S<sub>N</sub>2 pathway is not favourable for aromatic systems
Could a diaryl ether be easily cleaved using this method ?  No, since it would require an S<sub>N</sub>1 or S<sub>N</sub>2 type reaction on one of the aryl rings

Related reactions

MECHANISM FOR ACID CLEAVAGE OF ARYL ETHERS
Step 1:
An acid/base reaction. Protonation of the ether oxygen to make a better leaving group. This step is very fast and reversible.  The lone pairs on the oxygen make it a Lewis base.
HX ether cleaveage
Step 2:
The bromide ion functions as the nucleophile and attacks to displace the good leaving group, neutral phenol molecule, by cleaving the C-O bond. This results in the formation of an alkyl bromide and a phenol. 

 

Claisen Rearrangement of Aryl Allyl Ethers:

the Claisen rearrangement
Reaction type : Electrocyclic reaction or sigmatropic rearrangement

Summary

Caution: Do not confuse this reaction with the Claisen condensation of esters.
 
 
MECHANISM OF CLAISEN REARRANGEMENT 
Step 1:
An electrocyclic process. Push those electrons around the 6 membered ring.... Best appreciated by starting the electron flow by having the aromatic C=C attacking the allyl C=C and displacing an O leaving group....
Claisen rearrangement of allyl aryl ethers
Step 2:
Tautomerization of the ketone (actually a dienone) to the more stable aromatic enol, the phenol.