THE KANSAS UNIVERSITY 

 SCIENCE BULLETIN. 



Vol. XIII.] July, 1922. [No. 10. 



On the Preparation of the Aryl Isothiocyanates. 



BY F. B. DAINS, R. Q. BREWSTER, C. P. OLANDER. 



THE aromatic mustard oils, RNCS, which have been the sub- 

 ject of many investigations on account of their reactivity, have 

 been prepared by a number of different methods. The most com- 

 mon one involves the synthesis of the disubstituted thioureas from 

 the amines and the subsequent splitting of the thioureas into aryl 

 isothiocyanates and the amine or some derivative. Thus thiocar- 

 banilide, when boiled with concentrated hydrochloric acid, 20 per 

 cent sulphuric acid or concentrated phosphoric acid gave phenyl 

 mustard oil and varying amounts of aniline and triphenyl guanidine. 



The yield of mustard oil, based on the aniline used, in general is 

 far from satisfactory on account of losses incurred in the prepara- 

 tion of the thiourea and the subsequent splitting with acid.^ 



An interesting modification in the preparation of these compounds 

 depends upon the action of acetic anhydride or an acid chloride such 

 as acetyl chloride upon the thiourea.- The acetyl derivative of the 

 thiourea, wiiich is first formed, readily breaks down into the mustard 

 oil and an acyl-aryl amide, 



RNHCSNCOCH3R = RNCS + RNHCOCH3. 



While the above methods are of general applicability, it is evi- 

 dent that only one-half of the original amine can be converted into 

 the isothiocyanate, and that it necessitates the synthesis of the sub- 

 stituted thiourea. 



Fortunately, however, H. S. Fry's-" interesting method for the 

 preparation of the diaryl thiocarbamides has made readily acces- 

 sible various thioureas that were difficult to obtain by the older 

 methods. 



1. J. 1858, 394. Z. 1869, 359. Ber. 15, 986 (1882). 



2. J. Chem. Soc, 59, 400 (1891). J. Am. Chem. Soc, 22, 188 (1900). 



3. J. A. Chem. Soc, 35, 1539 (1903). 



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