Reactions and characterisation of aromatic ethers

Purely aromatic ethers e.g., diphenyl ether), which are commonly encountered, are very limited in number. Most of the aromatic ethers are of the mixed aliphatic - aromatic type. They are not attacked by sodium nor by dilute acids or alkalis. When liquid, the physical properties (b.p., and n ) are useful constants to assist in their identification. Three important procedures are available for the characterisation of aromatic ethers. 

Cleavage with hydriodic acid. Aromatic ethers undergo fission when heated with constant boiling point hydriodic acid  

The cleavage products are a phenol and an alkyl iodide, which will serve to characterise the ether. 

Experimental details can easily be adapted from those given under Aliphatic Ethers, Section 111,60, 2. 

Sulphonamides of aryl ethers. Aromatic ethers react smoothly in chloroform solution with chlorosulphonic acid at 0° to give sulphonyl chlorides, for example  

---