The Dow process is a method of phenol production through the hydrolysis of chlorobenzene.
Benzene can be easily converted to chlorobenzene by nucleophilic aromatic substitution via a benzyne intermediate.[1] 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.[2] When 1-[<sup>14</sup>C]-1-chlorobenzene was subjected to aqueous NaOH at 395 °C, ipso substitution product 1-[<sup>14</sup>C]-phenol was formed in 54% yield, while cine substitution product 2-[<sup>14</sup>C]-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).