— 7i — 



Mustard Oil. Whilst there is now hardly any doubt about the 

 structure of allyl cyanide, which, according to Kekule and Rinne 1 ) 

 has not the structural formula of an allyl compound 



CH 2 = CH — CH 2 — CN, 

 but that of crotonitrile 



CH 3 — CH == CH — CN, 



since F. Lippmann 2 ) and F. Schindler 3 ) have also supplied an 

 unobjectionable proof in favour of the formula drawn up by Kekule 

 and Rinne, nothing is as yet known of the reaction mechanism during 

 the formation of this cyanide from the allyl halogenides. 



Kekule and Rinne did not explain the re-arrangement which 

 must be assumed to occur in the formation of allyl cyanide, and 

 Lippmann only called attention to the analogy between the atomic 

 displacement in this case, and the one which occurs in the con- 

 version of safrol to isosafrol. 



For this reason, C. Pomeranz 4 ) has made experiments with the 

 view of clearing up this remarkable reaction, for which he prepared 

 the allyl cyanide according to Lippmann from allyl bromide and 

 potassium cyanide. He then found that for the formation of croto- 

 nitrile from allyl halogenides and potassium cyanide, the presence of 

 water is a preliminary condition, and he thus supplied a simple 

 explanation of the reaction - mechanism. The HCN formed by 

 hydrolysis from the potassium cyanide acts simultaneously with KCN 

 on halogen allyl, with formation of propylene cyanide, which then 

 further reacts with the KOH also formed by hydrolysis, when the 

 water entering into reaction, to which in this process the part of a 

 catalyser belongs, is continuously re-formed. 



CH 2 :CH — CH 2 Br + KCN + HCN == CH 3 — CHCN — CH 2 CN + KBr 

 CH 3 — CHCN — CH 2 CN-fKOH = CH 3 — CH : CHCN -f KCN + H^O. 



When saponifying the crotonitrile with dilute sulphuric acid, liquid 

 isocro tonic acid is formed, which at higher temperature is converted 

 to solid crotonic acid. 



As, according to Will and Korner 5 ), allyl cyanide is formed by 

 the action of water on mustard oil, and (in accordance with what 

 is said above) is identical with crotonitrile, it is possible that natural 

 mustard oil is a mixture of propenyl and allyl isothiocyanate. Arti- 

 ficial mustard oil, which is of course obtained in a similar manner as 

 allyl cyanide, might possibly also contain the propenyl compound 

 CH 3 .CH:CHNCS. 



x ) Berl. Berichte 6 (1873), 3 86 - 



2 ) Monatsh. f. Chemie 12 (1891), 402. 



3 ) Ibidem, 410. 



4 ) Liebigs Annalen 351 (1907), 354. 

 6 ) Liebigs Annalen 125 (1863), 281. 



