516 W. A. Drushel — Substituted Aliphatic Acids. 



bromine solution, showing it to be free from ethylidene malonic 

 ester. 



(c) Unsxibstituted fatty acid esters. — The ethyl esters of 

 propionic acid, butyric acid, isobutyric acid and isovaleric acid 

 were obtained by esterifying these acids with absolute alcohol 

 in the presence of a current of absolute alcohol vapor. Ethyl 

 diethylacetate was prepared from acetoacetic ester by the suc- 

 cessive introduction of two ethyl groups, saponification with 

 concentrated alcoholic potassium hydroxide and esterification 

 of the resulting disubstituted acetic acid as described above. 



Hydrolysis of Esters. — The esters of this series were hydro- 

 lyzed in decinormal hydrochloric acid at 25°, 35° and 45° and 

 the velocity constants were calculated from the titration 

 formula for monomolecular reactions. On account of the small 

 solubility of some of these esters it was necessary to use 

 saturated solutions in order to give a sufficiently large 

 range in the titrations to secure satisfactory velocity con- 

 stants. The acid was warmed to the required temperature 

 in the thermostat and was then shaken for a minute 

 with an excess of the ester. The solution was filtered 

 through a wet filter paper in order to obtain a homogeneous 

 reaction mixture by removing the excess of undissolved ester. 

 The filtered mixture was returned to a flask in the thermostat 

 and the initial titration was made without delay. A 60 cm3 por- 

 tion of the filtered reaction mixture was sealed up in a tube 

 and placed in a water bath at 70° to 80° to be used after several 

 days for making the end titrations in duplicate. From time to 

 time 25 cm3 portions of the reaction mixture were withdrawn 

 from the flask in the thermostat and titrated with N/20 or 

 N/25 barium hydroxide, using phenolphthalein as an indicator. 

 In order to permit all readings to be made upon the scale of a 

 50 cm3 standardized burette with such dilute alkali a bulb was 

 sealed to the top of the burette (as described in a former paper§ 

 from this laboratory) of such size ,as to allow the reading of 

 the initial titration to fall within the first 10 cra3 of the burette 

 scale. In this way it was possible to make titrations with a 

 sharp end-point and a minimum error due to burette readings 

 and at the same time a satisfactory range of titrations was 

 obtained for calculating the velocity constants. 



The time in minutes during which the course of each reac- 

 tion was followed by titrations and the constants calculated 

 from the velocity equation for monomolecular reactions are 

 recorded in detail in Table I, and in summary form in Table II. 

 In Table II are also recorded the temperature coefficients cal- 

 culated for the intervals from 25° to 35° and from 35° to 45°, 

 and the ratios of the velocity constants of cyan-substituted 



*Dean, this Journal, xxxvii, 331. 



