TRANSFORMATION OF NITROAMINES AND ALLIED SUBSTANCES, 121 
TaBLE IV. 
; Concentra- Speed of 
Medium Catalyst tion of Ac2O Hyurolyois 
50 per cent. acetic acid . — 0:083 k,;=0°016 
0:034M H,SO, 0-084 0-021 
007M HCl 0:083 0:022 
0-:071M HNO, 0-087 0:022 
90 per cent. acetic acid. | —_ 0:0815 0-0028 
0:033M HCl 0-081 0:023 
0:0165M HNO, | 0-083 0-0065 
0:033M HNO, = 0:0805 0:008 
0-066M HNO, | 0-079 0-012 
Glacial acetic acid . . . — |  0:0804 12% in 24 hrs. 
| 0-:002M H,SO, | 0:077 | 52% in 10 mins. | 
| 005M HNO, 0:08 32% in 24 hrs. 
Nitric acid only acts as other acids when ionised; the abnormality 
appears when the acid is partially or wholly unionised. On diluting a 
solution of glacial:acetic acid containing nitric acid to 50 per cent. acetic 
acid, hydrolysis follows at the same rate as if nitric acid had been added 
to acetic anhydride dissolved in a 50 per cent. acetic acid. This result 
does not suggest that the formation of such compounds as acety] nitrate, 
CH,.CO.O.NO., or diacetylorthonitric acid, (CH,.CO),N(OH)s, which 
have been described by Pictet and others, is the immediate cause of 
the peculiarity. For it would then be necessary to assume that these 
compounds yield acetic anhydride and nitric acid on diluting the medium 
with water. Moreover, the fact that the addition of a trace of sulphuric 
acid to the system containing nitric acid in glacial acetic acid is followed 
by the usual very rapid hydrolysis, indicates that the condition of the 
nitric acid only, and not that of the acetic anhydride, is the cause of the 
peculiarity. 
Discussion of Results —The suggestion, in a discussion of Rivett and 
Sidgwick’s results in the Annual Reports of the Chemical Society 
(1910), that the mechanism of the hydrolysis of acetic and other an- 
hydrides was not different from that of amides, esters, &c., as these 
authors had supposed, has been verified by our experiments. Since the 
reaction of acetic anhydride with hydroxy compounds (Franchimont, 
Skraup, and others), and with amino compounds, weak bases (Orton 
and Smith), is enormously accelerated by strong acids, it was to be 
expected that its reaction with water would be similarly influenced. 
In recent years the mechanism of such reactions has received 
much attention, and it has been shown, more especially in the case of 
esterification (Lapworth, Goldschmidt, and others), that the reaction 
may proceed in various ways, depending on the medium, presence or 
absence of other substances (acids and other catalysts). Following the 
suggestion of these researches the hydrolysis of acetic anhydride may be 
represented by one or other of the equations : — 
(i) Ac,O + H,O = 2AcOH ; 
(i) Ac,O + H,O + H’ = 2AcOH + H'; 
(ii) Ac,O + H,O + HX = 2AcOH + HX; 
(iv) Ac,O + H,O + (OH)’ = 2AcOH + (OH)’. 
