106 KELLER AND MA AS — DIMETHYL RACEMIC ACID. [April 7, 



Student of organic chemistry. Nevertheless only meagre descrip- 

 tions of the manner in which they have been applied in the various 

 cases are to be found in the special literature of the subject, and 

 no little difficulty was experienced in ascertaining the conditions 

 favorable to the formation of the dicyanh)4drin of diacetyl and its 

 conversion into dimethyl racemic acid. 



Numerous and varied were the attempts to effect a quantitative 

 union of the diketone with hydrocyanic acid, but in no case did 

 the yield of the dicyanhydrin exceed 30% of the theoretical. 

 Large quantities of other products, among them the monocyan- 

 hydrin, were always formed. The method generally recommended, 

 that of Wislicenus and Urech/ in which the compound containing 

 the ketonic group, CO, is made to react with hydrocyanic acid 

 in the nascent state, gave very poor results, and the only way in 

 which larger quantities of the desired product could be obtained, 

 was that originally used by Fittig and Keller. 



It consists in mixing diacetyl with aqueous hydrocyanic acid. 

 The best results were obtained by adhering to the following direc- 

 tions : The diketone in portions of about 20 grammes is gradually 

 added to a 30% solution of hydrocyanic acid, the heat of the 

 reaction being checked by cooling with water. The mixture is 

 then placed into a pressure bottle and heated in the water bath at 

 about 60° for some hours. The product of the reaction may now be 

 extracted with ether (in which it is quite soluble), or it may be 

 directly converted into dimethyl racemic acid by treating the solu- 

 tion with hydrochloric acid. The former seems preferable, since 

 it facilitates the purification of the final product. 



The saponification of the crystallized dicyanhydrin presents no 

 diificulties. Recent experiments have shown that it proceeds 

 rapidly and nearly quantitatively, when the substance is heated with 

 ordinary hydrochloric acid under pressure at 100°. After remov- 

 ing the excess of hydrochloric acid by evaporation on the water 

 bath, the residue, containing much ammonium chloride and some 

 tarry matter, is dissolved in water, the solution filtered, and the 

 filtrate carefully neutralized with baryta water. It is then boiled 

 with further additions of baryta (to decompose the ammonium 

 chloride), and allowed to stand after having been made slightly 

 acid with acetic acid; barium dimethyl racemate separates as a 



*Liebig's Annalen der Che?nie, Vol. 164, p. 255. 



