278 ORGANIC CHEMISTRY 



accelerates the reaction velocity in either direction to the same 

 extent. In the third place, the catalytic agent appears to act by its 

 presence simply; it appears, at least, to remain unchanged throughout 

 the course of the reaction. These three properties have been assumed 

 by some to be necessary and typical characteristics of catalytic action. 

 But in this investigation, in order not to overlook possibly the real 

 answer to our problem, the vital fact of acceleration alone was con- 

 sidered as characteristic and it was left to the rigorous application of 

 well-known fundamental laws of chemistry to develop why, inci- 

 dentally, in this and similar cases the equilibrium is not disturbed 

 sensibly and why the catalyzing acid appears to have no share in the 

 reaction. From this point of view, in endeavoring to imagine just 

 how an acid could affect the speed of the above reaction, the most 

 fundamental fact concerning acids was recalled, the fact that they 

 have the power to form salts with bases and oxides. Here we have the 

 acid and the oxide, and the idea was at once suggested that methyl 

 acetate has basic properties and that salt formation with the acid 

 is the cause of its catalysis. It was clear, however, that the basic 

 functions of a substance like methyl acetate must be far too weak for 

 quantitative measurements of its constants and for a rigorous quan- 

 titative test of the idea just developed. Under these circumstances it 

 was thought best to study all these conditions in a class of closely 

 related bodies, the imido-esters, with which quantitative measure- 

 ments of all important factors could readily be carried out. As the 

 name implies, these are esters in which we have an imide group 

 (: NH), replacing the oxygen atom of the ester, as in imidomethyl 

 acetate, CH 3 C( : NH)OCH 3 . They are markedly basic substances 

 which form well-defined salts. The free bases, for instance benzimido- 

 esters, are very slowly decomposed by water, chiefly according to the 

 reaction 



C 6 H 5 C(: NH)OCH 3 + H 2 0->C 6 H 5 CONH 2 + CH 3 OH (1) 

 and yet more slowly according to 



C 6 H 5 C(: NH)OCH 3 + H 2 O-C 6 H 6 C0 2 CH 3 -f NH 3 (2) 



Both reactions are practically non-reversible. The addition of 

 hydrochloric acid enormously increases the velocity of the second 

 reaction, and it becomes almost the exclusive one. Again the question 

 arises, how does the acid accelerate the action. Of course the acid 

 forms the hydrochloride, but as imido-esters are weak bases we have 

 in the aqueous solution partial hydrolysis and a condition of equilib- 

 rium according to 



C 6 H 5 C (NH 2 C1)OCH 3 + H 2 <= C 6 H 5 C (NH 2 OH)OCH 3 + HC1 (3) 



The reaction presents, therefore, at least three possibilities, the 

 velocity may be proportionate to the concentration of the salt 



