( 361 ) 



XVII. — Electrolytic Synthesis of Dibasic Acids. By Professor A. Crum Brown and 

 Dr James Walker. II. On the Electrolysis of the Ethyl-Potassium Salts of 

 Saturated Dibasic Acids with Side Chains, and on Secondary Reactions 

 accompanying the Electrolytic Synthesis of Dibasic Acids. 



(Read 6th April 1891 and 10th January 1893.) 



In our former paper # we described the results obtained by electrolysing concentrated 

 aqueous solutions of the ethyl-potassium salts of normal saturated dibasic acids. The chief 

 products were shown to be diethyl compound ethers of the same homologous series, and 

 the formation of these compound ethers was shown to occur in accordance with the 

 equation: 2C 2 H s -0-CO-R"-CO-0- =C 2 H 5 -0-CO-R // E // CO-0-C 2 H 5 + 2C0 2 . We now find 

 that precisely similar results are obtained by electrolysing the corresponding compounds 

 derived from saturated dibasic acids with side chains. We have thus been able to effect 

 the synthesis of acids of the succinic acid series, in which hydrogen is symmetrically 

 replaced by alcohol radicals of the form C n H 2u+1 . 



Synthesis of the Symmetrical Dimethyl-succinic Acids. 



Ethyl-potassium methylmalonate can be easily prepared by the general method detailed 

 in our former paper, and closely resembles the ethyl-potassium salts there described. 

 150 grammes of this salt were dissolved in 100 grammes of water, and subjected to 

 electrolysis in the manner described in our former paper. When the reaction was com- 

 pleted, the ethereal layer was separated from the aqueous solution, the latter was shaken 

 up with ether, and the ethereal extract added to the ethereal layer. The combined ethereal 

 solution was dried, and the ether distilled off on the water bath. The oily substance 

 remaining in the flask weighed 60 grammes and was nearly colourless. On fractionating 

 it, the greater part, 34 grammes, distilled between 200° and 220° at atmospheric pressure. 



This portion was collected by itself, and saponified by boiling it for two hours with 

 excess of alcoholic potash. The alcohol was removed by heating the solution on the 

 water bath, water being added from time to time, and the aqueous solution was then 

 decomposed by the addition of acid, when a white flocculent mass separated. The acid 

 thus obtained contained a small quantity of a syrupy substance, which was easily removed 

 by spreading the acid on a porous earthenware plate. 



Assuming that the electrolysis took a course similar to that observed in the cases 

 described in our former paper, the acid thus obtained ought to consist mainly of sym- 



* Trans. Eoij. Soc. Edin., vol. xxxvi. p. 211. 

 VOL. XXXVII. PART II. (NO. 17). 3 G 



