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. Chlorobenzene is treated with aqueous sodium hydroxide at 350 ðC and 300 bar or molten sodium hydroxide at 350 ðC to convert it to sodium phenoxide, which yields phenol upon acidification. When 1-[<sup>14</sup>C]-1-chlorobenzene was subjected to aqueous NaOH at 395 ðC, ipso the substitution product 1-[<sup>14</sup>C]-phenol was formed in 54% yield, while the cine substitution product 2-[<sup>14</sup>C]-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<sub>N</sub>Ar).