Phelps and Eddy — Hydrobromic Acid. 281 



Art. XXXI. — Researches on the Influence of Catalytic 

 Agents in Ester Formation. Hydrobromic Acid and 

 Zinc Bromide in the Formation of Ethyl Benzoate / by 

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



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



Goldschmidt* has measured the rate of esterification of ben- 

 zoic acid with ethyl alcohol, using hydrochloric and hydrobro- 

 mic acids as catalyzers. The results in the use of these two 

 catalytic agents for a temperature of 25° are so nearly the 

 same that he concludes that hydrochloric and hydrobromic 

 acids under the conditions of his experiments have the same 

 efficiency as catalytic agents in ester formation. Goldschmidtf 

 and many others, from similar physico-chemical measurements 

 given in recent literature, have concluded that the efficiency of 

 a given catalyzer depends upon the concentration of the cata- 

 lyzer and upon the degree of dissociation of the catalyzer in 

 alcoholic solution. 



The amount of ester formed froni benzoic acid in presence 

 of sulphuric acid, or hydrochloric acid, or hydrochloric acid 

 and zinc chloride as catalyzers, with different amounts of ethyl 

 alcohol acting for different lengths of time, has been shown in 

 a former paper % in this Journal. The esterification of the ben- 

 zoic acid was made in flasks specially arranged as illustrated 

 in an earlier paper§ in this Journal, where the action of zinc 

 chloride and hydrochloric acid, as catalyzers, was shown in the 

 formation of ethyl succinate. The results given in the paper 

 concerning the esterification of benzoic acid show that under 

 the conditions of the experiments made, increasing the concen- 

 tration of the catalyzers up to a certain limit increases the 

 amount of ester produced with a given amount of alcohol acting 

 in a given time on a given amount of benzoic acid. Further 

 increase in. the amount of catalyzers beyond this limiting con- 

 centration caused a decided falling off in the amount of ester 

 produced. And, finally, the results referred to show that the 

 yields of ester produced bear no relationship to the degree of 

 ionization of the catalyzer. For example, hydrochloric acid 

 dissociates to a greater extent than sulphuric acid, but with 

 hydrochloric acid as a catalytic agent yields beyond 90*4 per 

 cent were not obtained even when a mass of 50 grm. of ben- 

 zoic acid was treated with 400 cm3 of alcohol containing 25 per 

 cent of hydrochloric acid during eight and a half hours, inter- 

 polating a fractionation under diminished pressure to remove 

 low-boiling products, especially whatever water formed during 



*Berichte, xxviii, 3218. f Ibid., xxxix, 711. 



% This Journal, xxv, 39. § This Journal, xxiv, 194. 



Am. Jour. Sci. — Fourth Series, Vol. XX YI, No. 153. — September, 1908. 

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