Y an Name and Maryott — Chlorination of Benzene. 153 



Art. XVI. — On the Mechanism of the Chlorination of Ben- 

 zene in the Electrolytic Cell; by R. G. Van Name and 

 Carlton H. Maryott. 



[Contributions from the Kent Chemical Laboratory of Yale Univ. — ccxl.] 



As a result of the success attained in the use of electrolytic 

 oxidation and reduction processes in the preparation of organic 

 compounds, attention has been drawn from time to time to the 

 possibility that the development of electrolytic methods of 

 chlorination might yield results of practical value. Thus 

 Nernst * in 1897, in referring to the untried possibilities of 

 such methods, expressed the conviction that it would prove 

 practicable, in the chlorination of organic compounds, to obtain 

 every possible stage of chlorination by varying the electrode 

 potential. Up to the present time, however, the literature 

 upon the subject of electrolytic chlorination and bromination 

 has remained very limited, and, apparently, experimental 

 investigation along these lines has met with indifferent success. 



As early as 1852, Richef obtained monochlor-acetone by 

 electrolysis of a mixture of aqueous hydrochloric acid and ace- 

 tone, and by a similar method, using hydrobromic acid, pre- 

 pared monobrom-acetone. These methods were further studied 

 at a much later date by Richard % . In 1901, Zehrlant, § 

 by electrolyzing 4-normal hydrobromic acid containing phenol, 

 obtained a twenty per cent yield of bromphenol, and showed 

 moreover that the depolarizing action of the phenol toward 

 bromine produced a marked depression of the anode potential. 



SchleuderbergJ in 1908, described a series of experiments 

 on the electrolytic chlorination of acetic acid, benzene and 

 toluene. Of the methods tried by him the following gave the 

 best results : Acetic acid saturated with zinc chloride gave a 

 maximum current yield of 12*9 per cent ; benzene, dissolved in 

 ether saturated with zinc chloride, yields of 76 and 80 per cent ; 

 toluene, mixed with a concentrated aqueous solution of hydro- 

 chloric acid and kept at the boiling temperature, yields of 50 

 to 70 per cent. These current yields are calculated from the 

 total amount of combined chlorine exclusive of chloride, and 

 therefore do not necessarily refer to a single product. 



There are obviously two ways in which chlorination may 

 take place in the electrolytic cell ; (a), by a strictly electro- 

 lytic process, confined to the surface of the anode, as in the 

 case of electrolytic oxidation ; or (bj, by the secondary action 

 of the dissolved chlorine gas previously set free by the current 



*Ber. xxx, 1547. fComp. rend., xlix, 176. 



{Comp. rend., cxxxiii, 878 (1901). gZeitschr. f. Elektrochem, vii, 501. 



|| Jour. Phys. Chem., xii, 583. 



Am. Jour. Sci.— Fourth Series, Vol. XXXV, No. 206. 

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