Phelps and Eddy — Purification of Esters. 253 



Art. XXVI. — Concerning the Purification of Esters; by 

 I. K. and M. A. Phelps and E. A. Eddy. 



[Contributions from the Kent Chemical Laboratory of Yale Univ.— clxxxii.] 



Quantitative studies of the ester reaction were made under 

 the direction of one of us and published earlier in this Jour- 

 nal.* In that work the exactness was shown with which in 

 the preparation of the ethyl esters of succinic, malonic and 

 benzoic acids, the crude product of esterification obtained in 

 the special form of apparatus used, may be treated to isolate 

 the pure ester. In brief this treatment consisted in shaking 

 out the crude ester with ether, in the presence of an excess of 

 sodium carbonate in solution, distilling off under diminished 

 pressure the low boiling point products, and, finally, the ester 

 which was collected and weighed. This method of purifying 

 esters is a modified form of the procedure in common use for 

 isolating a pure ester from the crude product obtained during 

 esterification. Othersf have separated by distillation under 

 diminished pressure the water taken up by the ether during 

 the shaking out of the crude ester from the sodium carbonate 

 solution. This method of removing the water at as low a 

 temperature as possible, so that hydrolysis may not take place, 

 is particularly adapted for use in a quantitative study of the 

 ester reaction. The organic acid unesterifled and the mineral 

 acid used as a catalyzer is commonly removed by treatment 

 with sodium or potassium carbonate. Where the esters are 

 soluble in water Fischer and SpierJ varied the procedure by 

 treating the crude producf from esterification with an excess 

 of pulverized potassium carbonate, and removed, after long 

 shaking, the potassium salt by treatment with ether. The 

 filtrate was freed from ether on a water bath and fractionated 

 under diminished pressure. 



A study is given here of the exactness with which dry 

 potassium carbonate may be used in isolating succinic, malonic 

 and benzoic ethyl esters impure with alcohol, water, unesteri- 

 fied organic acid and small amounts of mineral acid. For this 

 purpose mixtures of the purified esters were made with the 

 substances, as shown in the table, and the ester separated and 

 weighed. 



Definite portions, 75 grm. each, of carefully purified diethyl 

 succinate, diethyl malonate, or ethyl benzoate were placed in a 

 Claisen flask of 250 cm3 capacity, chilled in ice, together with 

 2 grm. of the corresponding acid, 2 cm3 of concentrated hydro - 



* This Journal, xxiii, 368 ; xxiv, 294 ; xxv, 39 ; xxvi, 143. 

 f J. Am. Chem. Soc, xxiii, 1105, 1896. 

 JBerichte, xxviii, 3252. 



