Simple aryl halides do not react with nucleophiles under normal conditions. However, the reaction can proceed under drastic conditions involving high temperatures and high pressureto give the substituted products. For example,chlorobenzene is converted tophenol usingaqueous sodium hydroxide at 350 °Cunder high pressure by the Dow process. The reaction follows an elimination-addition mechanism involving a benzyne intermediate. Here, the chloride ion is eliminated to generate the benzyne intermediate. The benzyne intermediate then reacts with the base, followed byan acid workup thatgenerates phenol as the final product.