TRANSFORMATION OF NITROAMINES AND ALLIED SUBSTANCES. 117 
of a primary reaction of the chloroamine and hydrogen chloride, the 
presence of which is essential, thus :—~ 
Ar. NClAc + HCl Ar.NHAc + Cl,-—~— ClAr. NHAc + HCl. 
Whether a true intramolecular change is possible under certain 
conditions has not yet been discovered, but it must not be supposed 
that the possibility is excluded. 
The conversion of the nitroaminobenzenes into the isomeric nitro- 
anilines offers a very marked contrast. 
(i) All acids, and not one specific substance, bring about the trans- 
formation. The relative effectiveness of different acids is generally pro- 
portional to their activities in other processes. Moreover, when no side- 
reactions occur, the speed follows an equation of the first order, and, 
for a monobasic acid, is proportional to the second power of the con- 
centration, at least in aqueous and dilute acetic acid solution. 
(ii) Although there is evidence, but of no certain kind, that the 
nitration of another substance by a nitroamine can occur (for example, 
of acetanilide or 2: 4-dichloroaniline by s-tribromonitroaminobenzene), 
under certain narrowly defined conditions, there is nothing correspond- 
ing to the remarkable chlorination of one anilide by the chloroamine of 
another, which has been described. No radicle (ion) or substance which 
is a powerful nitrating agent appears to be free in the system. 
(iii) The solid crystalline nitroamine changes into the nitroaniline, 
the crystals of the latter apparently growing out of the former in the 
presence of gaseous hydrogen chloride in a P,O,-dry atmosphere.* 
(iv) Although nitrous acid appears during the transformation, and 
diazonium salts are produced, the presence of urea in the system does 
not affect in any way the speed or the products of the change. 
(v) The nature of the nitroamine and of, the catalyst has a very 
marked effect on the extent of the side-reaction in which the diazonium 
salt is produced. The maximum amount of diazonium salt is found 
with 2: 4-dichloronitroaminobenzene, much less with the correspond- 
ing 2: 4-dibromo compound, and none with 1-methyl-3-bromo-4-nitro- 
aminobenzene. 
The nature of the catalyst has a similar influence. When nitric 
acid is the catalyst no appreciable quantity of diazonium salt can be 
found. In the presence of perchloric acid, the maximum amount of 
diazo compound is produced; hydrogen chloride yields less and sulphuric 
acid still less. The ratio of diazonium salt to nitroaniline for a given 
catalyst appears to be independent of the concentration of the catalyst 
or the composition of the medium; thus in the case of hydrogen chloride 
and 2 :4-dichloronitroaminobenzene in various mixtures of acetic acid 
and water, the ratio, nitroaniline/diazonium salt=3°7/1. 
Conclusion.—So far as the evidence goes, the provisional conclusion 
may be drawn that the conversion of nitroaminobenzenes into nitro- 
anilines differs from the conversion of chloroamines, and may probably 
1 Reports, 1909, 
