— 84 — 



When the above fraction was brominated in chloroform solution, 

 and exposed for a considerable time to a low temperature, a small quantity 

 of a solid brominated product was obtained which, however, decomposed 

 immediately in contact with atmospheric air. Although the thio-urea is a 

 body with well-defined characteristics, it would have been highly desirable 

 if another derivative had been available from which to identify the crotonyl 

 mustard oil in question. This is especially the case in view of the close 

 correspondence which exist between the solubility, power of crystallisation, 

 m. p., 8jc, of the thio-urea and of the same derivatives of allyl mustard 

 oil, certain isomeric crotonyl mustard oils and some of the higher members 

 of the methane series (n-butyl and secondary-butyl thio-urea). So far, 

 however, no such other derivative has been discovered. Quite recently 

 Roshdestvensky 1 ) has recommended, for the purpose of identifying certain 

 alcohols and mercaptanes, the preparation of their thio- or dithio- 

 urethanes, the basis of this recommendation being to allow alcoholates or 

 mercaptides to react upon mustard oils, with heating if necessary, and to 

 separate the product by dilute acids from the sodium compounds which 

 are formed. From borneol-sodium and allyl mustard oil Roshdestvensky, 

 by this method, has prepared allyl thio-carbaminic acid bornyl ester which, 

 when recrystallised from dilute alcohol, presents itself in colourless crystals, 

 m. p. 59 to 60°. We have applied this same reaction to our crotonyl 

 mustard oil, by allowing equal molecules of mustard oil and borneol- 

 sodium in benzene -alcohol solution to act upon each other with sub- 

 sequent heating. After cooling, the mixture was slightly acidulated, the 

 reaction -product being isolated by extracting with ether. The crotonyl 

 thio-carbaminic acid bornyl ester, purified from dilute alcohol, melted at 

 55 to 56°, but it also is not very suitable for the identification of the 

 corresponding crotonyl mustard oil, because its m. p. differs but little 

 from that of the allyl derivative. 



As regards the constitution of the crotonyl mustard oil in question, 

 nothing can be said definitely up to the present, particularly so because 

 neither a synthetic nor a natural oil of similar properties and yielding 

 the same derivatives has yet been met with. In so far as it is per- 

 missible to draw any conclusions from the scanty literary references to 

 synthetic crotonyl mustard oils or crotonylamines (the products which 

 are used for building up from the former), it would appear that the crotonyl 

 mustard oil referred to above does not represent a compound of normal 

 constitution. But it must be borne in mind that our present data relating 

 to the constitution of these bodies are much in want of confirmation. We 

 have also attempted to prepare, for purposes of comparison, a synthetic 

 crotonyl mustard oil, for which purpose, in view of the process of its pre- 

 paration, the normal constitution would probably be indicated in the first 



*) Journ. russ. phys. chem. Ges. 41 (1909), 1438; quoted from Chem. Zentralbl. 1910, I. 910. 



