TRANSFORMATION OF AROMATIC NITROAMINES, ETC. 87 



in this solvent, the insoluble p-chloro-derivative separating imme- 

 diately. With the chloroamine there is no immediate reaction, then 

 after an interval, extending occasionally to days, a change begins, 

 which finally attains considerable speed (Diagram I. fig. 2); crystals 

 of p-chloroacetanilide appear as soon as saturation for this substance 

 is reached. If the quantity of chlorine suffices, further chlorination 

 of this compound, and still more, of the soluble o-chloro-derivative 

 which is produced simultaneously, follows. 



In both reactions the halogen attacks either a minute quantity of 

 anilide present with the chloroamine, or, more probably, a trace of 

 some impurity, yielding hydrogen chloride or bromide, which then 

 reacts with the chloroamine. In carbon tetrachloride it has been 

 shown (by the aspiration-method) in the case of anilides which do 

 not chlorinate, that the reaction, Ar.NClAc+HCl = Ar.NHAc + Cl 2 , is 

 quantitative. 



In the case of bromine the reactions are (after the formation of a 

 trace of hydrogen bromide) : - — 



Ar.NClAc + HBr = Ar.NHAc + BrCl = BrAr.NHAc + HC1 ; 

 Ar.NClAc + HC1 = Ar.NHAc + Cl 2 ; Cl„ + Br., = 2BrCl. 



Bromine chloride has been shown to be stable in carbon tetrachloride 

 and other anhydrous solutions, and to be a most powerful brominating 

 agent of anilides. The reactions proceed until the bromide is exhausted, 

 when chlorination begins. 



These experiments show further that chloroamines cannot be directly 

 chlorinated or brominated. 



Comparison of the Direct Action of Chlorine on Anilides ivith the Conversion 

 of Chloroamines in the Presence of Hydrochloric Acid. 



1. In glacial acetic acid the two processes, chlorine on anilide 

 and hydrochloric acid on chloroamine, give an identical rate of 

 chlorination. It is a reaction of the second order, for acetanilide 

 k n = 40, and for p-chloroacetanilide k u = - 21. In glacial acetic acid 

 the equilibrium, Ar.NHAc + Cl 2 £ Ar.NClAc+HCl, gives an inappre- 

 ciable amount of chloroamine and hydrochloric acid. 



The effect of small quantities of water is to accelerate the chlorina- 

 tion in a direct ratio. But after the addition of 4 to 5 per cent, the water 

 begins to affect the equilibrium and favours the production of chloro- 

 amine and hydrochloric acid. 



The speed of chlorination when the system is made up of chloro- 

 amine and hydrochloric acid still continues to increase, but as the 

 curve I. shows, only to a composition of the medium 92 per cent, 

 acetic acid, when the speed begins to decrease. Curves II. and III. 

 show respectively the falling-off in two systems in the amount of 

 chlorine and anilide with dilution of the acetic acid. 



2. In dilute acetic acids the rate of formation of C-chloro- 

 derivatives is very different in the two cases. On bringing together' 

 anilide and chlorine a very rapid formation of both C-chloro- and 

 N-chloro-derivative occurs, a very small proportion of the chlorine 

 (measured by aspiration) remaining free in the system. The relative 

 proportions of the two compounds, which vary with the anilide and' 

 the composition of the medium, is shown in Table I. 



