Drushel and Holden — Hydracrylic Esters. 511 



Art. XL. — On the Preparation and Properties of Hydra- 

 crylic Esters ; by W. A. Dkushel and W. H. T. Holden. 



(Contributions from the Kent Chemical Laboratory of Yale Univ. — cclxxv.) 



The esters of hydracrylic acid have up to the present time 

 received but little attention, only the methyl and ethyl esters are 

 mentioned in the chemical literature. The direct esterification 

 of hydracrylic acid had apparently not been attempted until 

 one of us * prepared ethyl hydracrylate in this laboratory by the 

 direct esterification process. As described in the literature the 

 indirect methods of preparation are objectionable since the 

 esters are obtained in impure condition, containing impurities 

 not easily removable. Obviously mineral acids cau not be 

 used as catalytic agents in the esterification of hydracrylic acid 

 since under the necessary conditions hydracrylic acid is con- 

 verted into acrylic acid and the resulting esters are chiefly 

 acrylic esters. 



The object of this investigation was to study the direct 

 esterification of hydracrylic acid with the common alcohols, 

 and the properties of the series of esters prepared in this way. 

 Sodium hydracrylate was prepared from glycerine by the 

 methods fully described in our previous paper, f The impor- 

 tance of keeping the solution of sodium hydracrylate slightly 

 acid during evaporation is to be emphasized, since in alkaline 

 solution condensation products are formed and only very little 

 sodium hydracrylate is obtained. The best procedure appears 

 to be nearly to neutralize /3-iodopropionic acid with sodium 

 carbonate, taking care to leave the solution distinctly acid. 

 The solution is then treated with an excess of silver oxide 

 freshly prepared and free from alkali. In this way the result- 

 ing solution contains sodium hydracrylate with a little silver 

 hydracrylate. After filtering off the silver iodide the solution 

 is treated with hydrogen sulphide to decompose any silver salt 

 present. The silver sulphide is then filtered off and the filtrate 

 is usually sufficiently acid to permit evaporation to dryness on 

 the steam bath without the formation of more than very small 

 amounts of by-products. The dry sodium hydracrylate thus 

 prepared is further purified by recrystallization from 95 per 

 cent alcohol. The yield is almost quantitative. Weighed 

 portions of the purified and dried sodium hydracrylate were 

 dissolved in the least possible amount of cold water and treated 

 with a little less than the theoretical amount of 1:1 sulphuric 

 acid, keeping the reaction mixture cold during the process. 

 The water in the resulting mixture was evaporated off on the 

 steam bath attended by only a slight loss of hydracrylic acid, 

 leaving a residue of sodium sulphate and pure hydracrylic acid. 



*This Journal, xxxix, 113-121, 1915. f Loc! cit. 



