54 PROCEEDINGS OF THE AMERICAN ACADEMY 



III. 



CONTRIBUTIONS FROM THE CHEMICAL LABORATORY OF 

 HARVARD COLLEGE. 



RESEARCHES ON THE SUBSTITUTED BENZYL COM- 

 POUNDS. 



By C. Loring Jackson and Alfred W. Field. 



FOURTH PAPER. 



PARACHLORBENZYL COMPOUNDS. 



Presented December 12th, 1877. 



Parachlorbenzylchloride, C (i JI i ClCJI 2 CL In beginning these re- 

 searches, we had no idea that it would be necessary to investigate this 

 substance, as, since its discovery by Beilstein and Geitner,* it had been 

 prepared and studied by a great number of chemists, and had served 

 as the starting-point for the preparation of all the parachlorbenzyl 

 compounds known. But, on looking into the subject more carefully, 

 we found that it had been made invariably from the product of the 

 chloriring of toluol in the cold, which Hubner and Majertf have 

 proved, by their work on the sulpho-acids, is a mixture of ortho and 

 parachlortoluol ; while, more recently, Oscar Emmerling $ has shown 

 that the product from oxidizing it with potassic permanganate contains 

 more ortho than parachlorbenzoic acid. The parachlorbenzylchloride 

 of previous chemists, therefore, must have been contaminated with a 

 larger or smaller amount of the ortho compound, which escaped detec- 

 tion, because the method used by them to test the purity of their 

 preparations consisted in oxidizing with potassic dichromate and sul- 

 phuric acid, and, as this destroys the ortho modification completely, a 

 pure parachlorbenzoic acid was the only product. This oversight is 

 not surprising when it is borne in mind that the more important of 



* Beilstein and Geitner, Zeitschr. der Chem., 1866, p. 307 ; also p. 17. 

 t Hubner and Majert, Ber. D. Ch. G. vi. p. 790. 

 J 0. Emmerling, Ber. D. Ch. G. viii. p. 880. 



