M. Claus on the Synthesis ofCrotonic Acid. 309 



By treating cyanide of ethyle with potash, Frankland and 

 Kolbe obtained propionic acid ; and this reaction has been since 

 then very frequently used for passing from one alcohol to the acid 

 corresponding to the next higher homologous alcohol. Claus* 

 has succeeded in applying this reaction to the preparation of 

 crotonic acid, € 4 H 6 O 2 , starting from cyanide of allyle, € 3 H 5 CN. 

 The preparation of this latter substance was readily effected by 

 the action of cyanide of potassium on iodide of allyle. The 

 cyanide of allyle was then boiled in a retort connected with an 

 inverted condenser, until no more ammonia was disengaged, and 

 the odour of cyanide of allyle was no longer perceptible. The 

 contents of the retort were then neutralized with carbonic acid, 

 boiled, and filtered to remove carbonate of potash. The filtrate 

 was evaporated to dryness, and repeatedly crystallized to get rid 

 of the last portions of carbonate. The potash-salt thus purified 

 was decomposed by means of dilute sulphuric acid and distilled, 

 by which means an aqueous acid distillate was obtained that 

 was used for the preparation of the other salts. The decompo- 

 sition of cyanide of allyle by potash is as follows : — 

 G 3 H 5 €N + KHG + H 2 0=C 4 H 5 K0 2 + NH 3 . 



Cyanide of Crotonate of 



allyle. potash. 



The aqueous distillate thus obtained is a colourless pungent acid 

 liquid, with an odour resembling that of butyric acid, from which 

 the acid separates at 0° in small white crystals. 



The salts show in general great resemblance to the corre- 

 sponding compounds of acrylic acid. 



Michaelson has investigated propylic and butylic aldehydes f. 

 He heated a mixture of butyrate and formiate of calcium in the 

 expectation of forming butylic aldehyde, in accordance with the 

 following reaction, 



CHCa0 2 + € 4 H7Ca0 2 =C 4 H 8 + €Ca 2 3 , 

 Formiate Butyrate Butylic Carbonate 



of calcium, of calcium. aldehyde, of calcium. 



but found that along with the expected substance propylic alde- 

 hyde, € 3 H 6 ' 0, was also formed. 



About 80 grammes of the mixed salts were used in one ope- 

 ration. The product of the reaction was treated with oxide of 

 lead, and then rectified over chloride of calcium. It began to 

 boil at 62°, and at 90° two-thirds remained in the retort. The 

 distillate, on rectification, gave a product which boiled between 

 54° and 63°. The results of the analysis and vapour-density 

 determination of this substance agreed with those required for 



* Liebig's Annalen, vol. cxxxi. p. 58. 

 t Bull. Soc. Chim. Paris, vol. ii. p. 123. 



