Ethyl Hydracrylaie. 117 



(1 : 3) sulphuric acid in the o.old. The excess of water was 

 then evaporated off on the steam bath, the hydracrylic acid 

 was extracted from the residue of sodium sulphate with abso- 

 lute alcohol and the alcoholic solution of hydracrylic acid, free 

 from sulphuric acid, was used in the esterification experiments 

 to be described. 



2. The esterification of hydracrylic acid. — In the prepara- 

 tion of one sample of hydracrylic acid a very slight excess of 

 sulphuric acicl was used in liberating the hydracrylic acid. The 

 hydracrylic acid without purification from the trace of sulphuric 

 acid was esteritied by boiling with a large excess of absolute 

 alcohol for twelve hours without the addition of any catalyz- 

 ing acid. About two-thirds of the acid was esteritied, but a 

 relatively large proportion of the resulting ester proved to be 

 acrylic ester. A second sample of hydracrylic acid free from 

 sulphuric acid was esteritied by boiling with a large excess of 

 absolute alcohol in the presence of anhydrous copper sulphate 

 prepared by the gentle ignition of crystallized copper sulphate, 

 but not freed from the traces of sulphuric acid formed in the 

 process of dehydration. Here again the esterification pro- 

 ceeded rapidly until about 70 per cent of the acid was esteri- 

 tied, but as before, the result was a mixture of acrylic and 

 hydracrylic esters. It seemed, therefore, necessary to avoid 

 even very small amounts of mineral acids in the esterification 

 of hydracrylic acid in order to prevent the formation of acrylic 

 ester. 



Wislicenus* suggested the use of the vapor from boiling 

 absolute alcohol as an efficient dehydrating agent in esterifica- 

 tion. The inefficiency of absolute alcohol alone as well as that 

 of absolute alcohol vapor passed through the reaction mixture 

 and the superiority of anhydrous copper sulphate as a dehy- 

 drating agent are shown in the following experiment : Thirty- 

 two grams of hydracrylic acid free from sulphuric acid were 

 first boiled, with a reflux condenser, with 200 cm3 of absolute 

 alcohol for three hours, giving 9"4 per cent of the theoretical 

 yield of ester ; at the end of six hours 17 per cent of the acid 

 was esterifL'd. Then the reaction flask was heated at 110° and 

 absolute alcohol vapor passed through the reaction mass, giv- 

 ing at the end of two hours 40 per cent of ester, and after two 

 hours more only 42 per cent of ester. The current of absolute 

 alcohol vapor was then discontinued and about 30 grms. of 

 anhydrous copper sulphate, free from sulphuric acid, were 

 added and the reaction mixture gently boiled, giving after 

 three hours 74 per cent of ester, and after three hours more 

 83 per cent of the acid was esteritied. The ester formed was 

 found to be hydracrylic ester free from acrylic ester. 



* Wislicenus, Ann. Chem. Pharin., clxiv, 181. 



