NITRATION THEORIES^77(41)(42)On this ground Seyewetz assumes that all nitro compounds with a free para or
ortho position can isomerize in the following way:
(43)Indeed Pascal [83] found that in the waste acid from the nitration of naphthalene
to dinitronaphthalene, the NH 3 content amounted to 0.001-0.002%, based on the
naphthalene used for nitration.
During the nitration of aromatic compounds a certain amount of diazo com-pounds as by-products can also be formed. This for the first time was described
by Weselsky as early as in 1875 [84] in the case of nitration of phenols with nitrogen
dioxide and of nitration of aromatic hydrocarbons by Titov and Baryshnikova [85].
Titov [39] explained the reaction as the result of reaction of nitroso compounds
with NO:I II
The diazo compound (I) can next be transformed into the phenol (II) (see also
[18a]).
In some experimental conditions aromatic hydrocarbons, particularly those
with alkyl side chains can form dark coloured, reddish-brown by-products on