ON THE TRANSFORMATION OF AROMATIC NITROAMINES. 105 
The Transformation of Aromatic Nitroamines and Allied 
Substances, and its Relation to Substitution in Benzene 
Derwatives.—Report of the Committee, consisting of 
Professor F. S. Krippina (Chairman), Professor K. J. P. 
Orton (Secretary), Dr. S. RuHEMANN, and Dr. J. T. 
HEWITT. 
The Acetylation of Anilines by Acetic Anhydride in the presence of 
Catalysts. 
(With W. H. Gray, M.Sc.) 
TuE accelerating action of catalysts on the interaction of acetic anhy- 
dride and hydroxy- groups has long been known: it was first observed 
by Franchimont' in the acetylation of cellulose, and was later noted 
by numerous observers.?,_ That catalysts had a similar effect in the 
action of acetic anhydride on the amino- group seems, however, to 
have been overlooked until Smith and Orton* made the discovery that 
negatively di-ortho- substituted anilines, such as s-tribromoaniline, can 
be acetylated at great speed at the ordinary temperature in the presence 
of sulphuric and other acids. 
Such anilines are particularly suitable for such an investigation as 
they react very slowly indeed with acetic anhydride at the ordinary 
temperature, and at higher temperature mainly yield diacetyl deriva- 
tives, Ar-NAc,; in the presence of a catalyst at low temperatures they 
yield, on the other hand, the monoacetyl derivative. Anilines with 
one ortho- position unoccupied form monoacetyl derivatives with such 
extreme ease that the presence of an acid is of no advantage, but, on the 
contrary, inhibits the reaction, most probably by forming stable salts 
which do not react with acetic anhydride. 
Such salts as sodium acetate have long been known as catalysts of 
the acetylation of phenols. We have found that various salts have 
a similar effect in the case of amines. Ferric salts are as pre-eminent 
in this capacity as in the bromination of acetic anhydride and other 
compounds, which we are investigating. 
An early attempt (Smith and Orton, loc. cit.) to throw light on the 
mechanism of such catalyses, using s-tribromophenol, demonstrated 
that acids varied greatly in catalytic effect; that the change was a re- 
action of the second order; that the speed was proportional to the 
concentration of the catalyst. 
To follow quantitatively the interaction of acetic anhydride and a 
di-ortho negatively substituted aniline has proved a very difficult 
matter. The small capacity for forming salts, which is an advantage 
in following the effect of acid catalysis on acetylation, is a barrier to 
the estimation of unchanged aniline by the diazo- method. Moreover, 
the slowness with which the anilide is hydrolysed equally prevents 
estimation of the extent of acetylation. 
1 Compt. rend., 1879, 89, 711. 
2 Skraup, Monatsh. 1898, 19, 458; Freyss, Bull. Soc. Ind. Mulhouse, 1899, 44; 
J. Thiele, Ber. 1898, 81, 1249; O. Stillich, Ber. 1903, 36, 3115; 1905, 38, 124; 
J. Boeseken, Recueil des Trav. Chim., 1911, $1, 350. 
5 Trans. Chem. Soc. 1908. 98, 1243 ; 1909. 95, 1060. 
