332 E. W. Dean — listers of Substituted Aliphatic Acids. 



Puchot."* Iso-butyl alcohol was oxidized with chromic acid 

 and the iso-butyl ester of iso-butyric acid thus formed. From 

 this the ethyl ester was obtained by the successive processes 

 of saponification by alkali, acidification, and treatment with 

 ethyl alcohol. This last esterification was conducted accord- 

 ing to the method of Wislicenus.f The purified product 

 boiled at 110°, which is the figure given in the literature. 



Ethyl alpha hydroxy-butyrate was obtained by the esterifi- 

 cation of acid purchased from Kahlbaum. After obtaining 

 unsatisfactory results from trials by most of the usual methods 

 the method of Bogojawlensky and Narbut;}: was found to be 

 well adapted to this case. The acid was boiled with absolute 

 alcohol in the presence of finely powdered anhydrous copper 

 sulphate. The resulting ester was purified by fractional distil- 

 lation and a sample obtained boiling between 162° and 164° 

 uncorrected. The temperature given in Beilstein is 165° 

 corrected. 



Ethyl beta hydroxy-butyrate was purchased from Kahlbaum 

 and was used without special purification. Its boiling point 

 was 178° to 180° uncorrected ; no value is given in Beilstein. 

 As a check upon the reliability of this commercial product 

 a small quantity was prepared by esterifying some of the 

 free acid by the copper sulphate method. One or two portions 

 of this, when hydrolyzed, gave constants approximately the 

 same as those of the Kahlbaum preparation. The freedom of 

 the latter from impurities of any other esters was also proven 

 by the regularity of its velocity constants. The presence of 

 another ester having a different rate of reaction would have 

 caused a progressive decrease in any series of these constants. 



Ethyl alpha hydroxy-iso-butyrate was also purchased from 

 Kahlbaum and was proven sufficiently pure by analysis and by 

 determination of its boiling point. The latter was 146° uncor- 

 rected, that given in Beilstein is 150° corrected. 



Procedure. 



The unsubstituted esters of this list have rather low solubil- 

 ities, so that it was found desirable to modify somewhat the 

 procedure | which had been used for acetates and propionates. 

 In cases where a solution of the ester six hundredths or more 

 normal can be prepared in decinormal hydrochloric acid, it is 

 simplest to titrate twenty -five cubic centimeter portions directly 



* Anal, de Chita, et Phys., (4), xxviii, 366. 

 f Ann. d. Chem. u. Pharm., clxiv, 181. 



\ Ber. xxxviii, 3344. See also Clenimenson and Heitman, Am. Chem. 

 Jour., xiii, 319. 



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



