jE. W. Dean — Esters of Substituted Aliphatic Acids. 331 



Art. XXVIII. — On the Hydrolysis of Esters of Substituted 

 Aliphatic Acids / by E. W. Dean. 



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



7. Hydrolysis in Acid and in Alkaline Solution of Ethyl Esters 

 of Hydroxy Butyric Acids. 



Acid Hydrolysis. 



Preliminary Discussion. 



The effect of the hydroxyl group upon the velocity of acid 

 hydrolysis has been shown* to be somewhat irregular in the 

 cases of acids of the acetic and propionic series. Ethyl glycol- 

 late is decomposed a little more rapidly than the acetate. Ethyl 

 lactate, the alpha hydroxy propionate, has a greater reaction 

 velocity at twenty-five degrees and a less at forty-five than has 

 ethyl propionate. This is due to the lower temperature coeffi- 

 cient of the hydroxy ester, but makes it immediately impossible 

 to state that the presence of this particular substituted group 

 facilitates the hydrolytic cleavage. Ethyl gly cerate, which is 

 the alpha, beta, di-hydroxy propionate, has relatively a very 

 low rate of hydrolysis, showing that the substitution of two 

 groups may produce an effect differing in order of magnitude 

 from that of one. 



In view of the above facts it was thought desirable to obtain 

 more data bearing upon this subject, and consequently meas- 

 urements have been made of the rates of decomposition of 

 several hydroxy butyric esters. Those which were examined 

 comprise the following list : 



Ethyl alpha hvdroxy-butyrate, CH a CH 2 CFT(OH)COOC,H 5 , 

 Ethyl beta hydroxy-butyrate, CH 3 CH(OH)CII 2 COOC a H 5 , and 



Ethyl alpha hydroxy-iso-butyrate, ^ 3 >C(OH)COOC 2 rI 6 . 



Ethyl normal butyrate and ethyl iso-butyrate were of course 

 hydrolyzed at the same time with these esters in order that the 

 comparisons made should deal with the results of measurements 

 made under identical conditions. 



Preparation of the Esters. 



Ethyl butyrate was the Kahlbaum preparation of commerce 

 which was carefully purified by washing and by fractional dis- 

 tillation. Boiling point, 118'5° to 119 5°. The figure given 

 in Beil stein is 119-9°. 



Ethyl iso-butyrate was prepared by the method of Pierre and 

 * This Journal, xxxiv, 293 ; xxxv. 486. 



