Dow process (phenol)

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

Benzene can be readily converted to chlorobenzene by nucleophilic aromatic substitution via a benzyne intermediate.¹ Chlorobenzene 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.² When 1-[¹⁴C]-1-chlorobenzene was subjected to aqueous NaOH at 395 °C, ipso the substitution product 1-[¹⁴C]-phenol was formed in 54% yield, while the cine substitution product 2-[¹⁴C]-phenol was formed in 43% yield. This indicates that an elimination-addition (benzyne) mechanism is predominant, with perhaps a small amount of product from addition-elimination (S_NAr).