Diphenyl Ether: Chlorobenzene and Phenol in Caustic Soda at 400 °C (Dow 1978)

Heat chlorobenzene with caustic soda solution to 400 °C under pressure and it gives phenol, with some diphenyl ether. Dow's William Smith found that adding phenol to the charge turns the run round: the phenol is used up and diphenyl ether becomes the main product. This follows his Example 2. It needs a sealed nickel-steel pressure reactor; phenol burns and poisons through the skin. Source: W. E. Smith (Dow), US 4,092,364 (1978). The choice of Example 2, making the caustic solution, and the boiling point are ours. Picture drawn by Youblob.