These three compounds are perhaps to be represented as orthoor as paraquinones (see papers by F.
Rosenstiehl (Jahres., 1869, p. 693) found also that different rosanilines were obtained according to whether orthoor para-toluidine was oxidized with aniline; and he gave the name rosaniline to the one obtained from aniline and ortho-toluidine, reserving the term pararosaniline for the other.
This change only occurs when the halogen atom is in the orthoor paraposition to the - N2 - group.
Concentrated acids convert them into the isomeric nitro-amines, the - NO 2 group going into the nucleus in the orthoor paraposition to the amine nitrogen; this appears to indicate that the compounds are nitramines.
This assumed that all coloured substances were derivatives of orthoor para-quinone (see Quinones), and although at the time of its promotion little practical proof was given, yet the theory found wide acceptance on account of the researches of many other chemists.
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