Drushel and Hill — Esters of Halogen Substituted Acids. 73 



In preliminary experiments, which were made to see if there 

 is any splitting out of halogen in the course of the reaction, 

 ISr/26 solutions of esters in N/20 acid were placed in the 

 thermostat and titrated from time to time with N/10 silver 

 nitrate solution, using an aqueous solution of potassium 

 chromate as an indicator. In the case of the monochlor- and 

 monobromacetic esters no increase in the free halogen acid 

 was observed even after several weeks. The iodo-esters, how- 

 ever, were apparently decomposed with liberation of iodine, 

 but Avhether through the decomposition of the acid set free by 

 hydrolysis or directly from the ester we have not at the 

 present time determined.* To prevent possible substitution 

 of chlorine for bromine in the monobromacetic esters, hydro- 

 bromic acid was used as a catalyzer ; as this has almost exactly 

 the same strength as hydrochloric acidf used with the other 

 esters, the difference in catalyzing effect is negligible. The 

 chlorformic esters, which we had intended to include in our 

 investigation, were rapidly decomposed with evolution of CO, 

 showing total decomposition according to the following equa- 

 tion : 



C1-C00C,H, -f- HOH >HC1 + CO, + C^H^H. 



Preparation of Esters. — The methyl and ethyl acetates 

 were prepared in part by the method of Phelps;}: and in part 

 by the method of Thomson. § The propyl and isobutyl 

 acetates were prepared by acting with acetyl chloride on the 

 corresponding alcohol. This reaction is rapid and practically 

 quantitative. The halogen substituted esters were generally 

 prepared by the action of chloracetyl chloride and bromacetyl 

 bromide on an alcohol. The methyl and ethyl esters of chor- 

 acetic acid, however, were prepared from chloracetic acid and 

 alcohol by the method of Thomson. The mixture of esters 

 with the excess of acid and alcohol was neutralized with 

 Na2C03 and diluted by pouring into a large volume of water. 

 The layers formed were separated and the ester was washed 

 with water, dried over CaCl, and fractionated. The part boil- 

 ing within 0"1° to 0"3° of the boiling point given in the litera- 

 ture was taken for the experiments. 



The halogen substituted acetic esters are pungent com- 

 pounds. When perfectly pure they are not disagreeable, but 

 after hydrolysis or before purifieation their vapors are very 

 irritating to the eyes and mucous membrane. As the vapors of 

 the impure ester contain excess of acid and the mixture of acid 

 and alcohol after hydrolysis have the same effect on the eyes, 



* This point will be investigated by the authors. 



fOstwald, Zeitschr. phvs. Chem., iii, 418. 



i This Journal, xxiii, 368, 1907. 



gThomsen's Thermoehemische Untersuchungen, iv, 201. 



