282 ORGANIC CHEMISTRY 



If we add hydrochloric acid some salt must be formed, which will 

 be almost completely hydrolyzed according to 



Cl OH 



I I 



CH 3 CO-0-CH 3 + H 2 <=> CH 3 CO-0-CH 3 + HC1 



I I 



H H 



Then according to Arrhenius's equation for hydrolyzed solutions 

 of salts of weak bases with strong acids we have 



(Posit.Ester Ion) = -^ X (Ester-y) X (H') 



K. 



For an almost completely hydrolyzed salt the change in the con- 

 centration of the ester will not be perceptible, y will be entirely 

 negligible, and we obtain then for the velocity of saponmcation of 

 methyl acetate in the presence of hydrochloric acid: 



^ap (HOD = *s.p X ^ X (Ester) X (HO X (H,0) 



By a comparison of the two velocity equations, for the reaction in 

 the presence of water alone and in the presence of added acid, we find 

 that the velocity must in fact increase directly proportionate to the 

 concentration of the hydrogen ions, since all other factors remain 

 unchanged. This consequence of our theory is evidently in perfect 

 agreement with the well-known experimental results. 



And now we come to the last important fact, namely, that the 

 reaction is a reversible one, viz.: 



CH 3 CO-0-H +CH 3 OH -CH 3 COOCH 3 +H 2 



and that the velocity of this reaction is also accelerated by the addi- 

 tion of hydrochloric acid. Following out our idea rigorously, this 

 increased velocity under the influence of an acid must be due to min- 

 imal basic properties of acetic acid or methyl alcohol. It could easily 

 be shown, if time permitted, that it is to the basic properties of acetic 

 acid that we must look in this instance. This conclusion is not so sur- 

 prising as it may appear at first glance, we have so many substances 

 that are both basic and acid, and 



Cl Cl 



CH 3 CO-0-H is not more different from CH 3 CO'0'CH 3 



H H 



Cl Cl 



than CH 3 .O.H is from CH 3 .O.CH 



I 

 H H 



