90 REPORTS ON THE STATE OF SCIENCE. 



of the chloroamine of another anilide and hydrochloric acid, show that 

 in this case the chloroamine of acetanilide may be formed, yet the 

 relation of the velocities of the C-chlorination in the various systems 

 make it impossible for the chlorination of the acetanilide to take place 

 by way of the chloroamine. If that were the route, the process could 

 not be faster than when the starting-point was the chloroamine of 

 acetanilide. Further, when on the other hand the chloroamine of 

 acetanilide and hydrochloric acid interact with p-chloroacetanilide in 

 50 per cent, acetic acid, a slow chlorination occurs, and, in spite of 

 the difficulty of isolating small quantities of 2 : 4-dichloroacetanilide 

 from such a mixture, its presence was undoubtedly demonstrated by 

 the isolation of the pure material; that is, some chlorination of 

 p-chloroacetanilide took place. 



Mechanism of Chlorination {and Brominalion) and of the Conversion of 



Chloroamines. 



The experiments recorded in the foregoing leave no doubt that the 

 chloroamines cannot be regarded as even occasional intermediaries, 

 much less necessary intermediaries in chlorination. They would 

 rather appear to be by-products. 1 



The residual valency of the nitrogen atom was urged by Armstrong 

 as the prime factor in bringing about the initial union of the substi- 

 tuting agent and the anilide. Such a substance would be, in chlorina- 

 tion, the compound, Ar.NHAcCL, identical with the complex formed 

 from chloroamine and hydrochloric acid, already referred to. 



If the existence of this reactive complex be assumed, our experi- 

 ments enable one to deduce a number of its properties. 



(i) The action of chlorine on acetanilide and p-chloroacetanilide in 

 various dilutions of acetic acid, show that the rate of formation and 

 of change of the complex into the substituted anilide must increase 

 rapidly with dilution of the acetic acid. 



(ii) The concentration of the complex (in any case minute) must 

 rapidly decrease with dilution of the acetic acid medium, in a system 

 which has attained equilibrium, since the velocity of C-chlorination in 

 a system prepared from chloroamine and hydrochloric acid decreases 

 with the dilution. 



(iii) Inasmuch as the rate of C-chlorination in diluted acetic acid 

 is so markedly faster when chlorine and anilide are allowed to interact 

 than when the system is prepared from chloroamine and hydrochloric 

 acid, the rate of change of the complex into a C-chloro-derivative must 

 be greater than into the N-chloro-derivative : — 



J^U Ar.NClAc + HC1. 

 Ar.NHAcC)., " 



" "^-* ClAr.NHAc + HC1. 



1 They Can Only be regarded as intermediaries when hypochlorous acid acts on 

 an anilide, for then the chloroamine only and no C-chloro-derivative is formed. 

 Introduction of hydrogen chloride is required, however, for the conversion of the 

 chloroamine into the C-chloro-compound. 



