Dow process (phenol)

The Dow process is a method of phenol production through the hydrolysis of chlorobenzene.

Details
Benzene can be easily converted to chlorobenzene by nucleophilic aromatic substitution via a benzyne intermediate. It is treated with aqueous sodium hydroxide at 350 °C and 300 bar or molten sodium hydroxide at 350 °C to convert it to sodium phenoxide, which yields phenol upon acidification. When 1-[14C]-1-chlorobenzene was subjected to aqueous NaOH at 395 °C, ipso substitution product 1-[14C]-phenol was formed in 54% yield, while cine substitution product 2-[14C]-phenol was formed in 43% yield, indicating that an elimination-addition (benzyne) mechanism is predominant, with perhaps a small amount of product from addition-elimination (SNAr).