TRANSFORMATION OP NlTROAMlNES AND ALLIED SUBSTANCES. 97 



2 :4-dichloro-a-naphthol is formed, and hence an equivalent quantity of 

 a-naphthol remains unchanged, a-naphthol can be quantitatively con- 

 vezted into 2 :4-dichloronaphthol by this method. 



Formation of Nit roam incs. (With Miss M. G. Edwards.) 



There is no easier way of preparing certain nitroaminobenzenes than 

 by treatment of the aniline in acetic acid solution with a mixture of 

 acetic anhydride and nitric acid in the same solvent. With di-ortho- 

 (negatively)-substituted anilines the yield of nitroamine is quantitative. 

 With other anilines the acetyl derivative is formed simultaneously, owing 

 to the more rapid interaction of acetic anhydride with anilines in which 

 an ortho position is unoccupied, or not occupied by a negative group. 

 The proportion of nitroamine to acetyl derivative can be to a certain 

 extent regulated by variation of the concentrations of the acetic anhy- 

 dride and nitric acid. 



It appears to be generally thought that the formation of the nitro- 

 amine is due to the dehydration of the aniline nitrate. There is, how- 

 ever, much evidence that such is not the case. 



1. It was shown by Smith and Orton 5 that all acids, except nitric 

 acid, acted as powerful accelerators of acetylation of anilines by acetic 

 anhydride. There is no formation of the anilide of the acid, of the type 

 corresponding to the nitroamine. 



2. Measurements have been made of the rate of the formation of 

 nitroamines by this method. In one series of experiments the anhy- 

 dride is added to a mixture of aniline and nitric acid in acetic acid; a 

 relatively slow regular formation of nitroamine follows. In other series 

 the anhydride and nitric acid are mixed in acetic acid and then added 

 to the solution of the aniline ; a very rapid formation of the nitroamine 

 takes place, the speed, however, falling off after about half the reaction 

 is over. 



This result obviously suggests that a compound of acetic anhydride 

 and the nitric acid is the nitrating agent. In the second series it can 

 be formed and reach a high concentration before it is brought in 

 contact with the aniline. This compound may be the compound pre- 

 pared by Pictet, 6 (CH 3 -C0 2 )N 2 (OH) 3 , or even acetyl nitrate. 



3. A remarkable confirmation of this view is found in some experi- 

 ments which have been recently carried out on the hydrolysis of acetic 

 anhydride (with Miss M. Jones). The anhydride was dissolved in a large 

 excess of acetic acid, which contains a small proportion of water, 0'12 to 

 0'2 per cent. The hydrolysis of acetic anhydride in this medium is 

 extremely slow at the ordinary temperature. In the presence of small 

 proportions (| to J gram molecular proportion) of all mineral acids, with 

 the exception of nitric acid, an extremely rapid hydrolysis occurs. 

 With nitric acid there is no acceleration, but even a retardation of the 

 hydrolysis. In dilute (80 per cent.) acetic acid there is no difference 

 between nitric acid and other acids. 



There seems little doubt then that nitric acid and acetic anhydride, 

 even when largely diluted with acetic acid, very rapidly react or 



s Trans. Chem. Soc, 1908 and 1909. ° Zentralblatt., 1903, ii., 1109. 



1911. H 



