108 



Dr. A. W. Hofmaim on the Aromatic Cyanates. [Nov. 24, 



III. " On the Aromatic Cyanates." By A. W. Hofmann, 

 LL.D., F.KS. Received July 30, 1870. 



The only member of this class which has hitherto been studied is the 

 phenylic cyanate. About twenty years ago I discovered this compound 

 among the products of a very complex reaction which took place on sub- 

 mitting to destructive distillation a substance which I then named ox- 

 amelanil or melanoximide*, but which at the present time would be con- 

 sidered as oxalyldiphenylguanidine. The phenylic cyanate, which I then 

 called anilocyanic acid, is formed only in very small quantity ; I never had 

 more than a few grammes of the substance in my possession ; and it was 

 only from the sharply defined properties of the body that I was enabled 

 to describe it correctly. 



Eight years later I again met with this compound. When I found that 

 diphenylsulphourea, by treatment with anhydrous phosphoric acid, split 

 up into aniline and phenylic mustard-oil, the idea naturally suggested 

 itself to utilize this reaction for the preparation of phenylic cyanate, by 

 distilling normal diphenylurea with anhydrous phosphoric acidf. 



In fact, phenylic cyanate can be prepared in this way. On heating dry 

 diphenylcarbamide with anhydrous phosphoric acid, the frightful odour of 

 the cyanate was immediately developed ; and on distilling the mixture of 

 the two bodies, the phenylic cyanate came over in colourless drops. 

 "When, however, the experiment was made on a somewhat larger scale, 

 the product was so small that I was compelled to consider this process 

 more as a mode of formation of the substance than as a method for its 

 preparation. 



Lately my experiments on the mustard-oils led me to a simple process 

 for the preparation of the phenylic cyanate and its homologues. 



In a former paper % I drew attention to the facility with which the mus- 

 tard-oils combine with a molecule of alcohol. When phenylic mustard- 

 oil is heated for a considerable time with alcohol, it yields the beautifully 

 crystalline half sulphuretted phenylurethane, which, when distilled alone, 

 or, still better, with phosphoric anhydride, again splits into its com- 

 ponents alcohol and phenylic mustard-oil. 



Taking into consideration the result of this experiment, ought we not 

 to obtain the phenylic cyanate on distilling phenylurethane with phos- 

 phoric acid ? 



Phenyl Series. 



Phenylurethane. — The phenylurethane is known ; I had already ob- 

 tained it in the above-mentioned researcn on tne phenylic cyanate. When 

 this substance was treated with methyl, ethyl, or amyl alcohol, the phenyl- 

 urethane of the methyl, ethyl, or amyl series was obtained §. Since then 



* Hofmaim, Ann. Chem. Pharm. vol. lxxiv. p. 9. 



t Hofmann, Proc. Boy. Soc. vol. ix. p. 275. 



} Hofmann, Berichte Deutsch. Chem. Gesell. Jahrg. ii. S. 116. 



§ Hofmann, Ann. Chem. Pharm. vol. lxxiv. p. 16. 



