Halogenation and opt. oxidn., of aromatic cpds. - with aq. hydrohalic acid and hydrogen peroxide, esp. for chloranil prodn.

摘要

Method for halogenation and/or halogenative oxidation of aromatic cpds. (I) which are reactive or have >=1 activating gp. (pref. OH, alkoxy or aryloxy) comprises reacting (I) with an excess of conc. hydrohalic acid and a stoichiometric or excess of conc. hydrohalic acid and a stoichiometric or excess amount of H2O2 at 0-100 degrees C. for 10 min. to 50 hr. (I) may have 1-4 additional substits. and reaction is opt. in presence of (a) an inert solvent which may or may not be miscible with water; (b) an emulsifier and (c) a catalyst. The solvent is pref. glacial acetic acid or CCl4 and the catalyst a di- or tri-valent metal halide, esp. MgCl2. Used esp. for making chloranil and bromanil or the corresp. hydroquinones. p-Chloranil is a dye intermediate, oxidising agent in the dye industry; plant-protection agent (fungicide) and a disinfectant for grain. High yields are obtd. without the use of toxic chemicals.