Laboratory Methods of Organic Chemistry - Sciencemadness Dot Org

THE BBNZIDINB KBAKKANGBMBNT
HH HH
H< •N.CO.CH,
\_/ H
HH HH
N.CO.CH3 —>
Cl
Cl..
NH2
.NH.CO.CH3 .
The rearrangement of aromatic nitrosamines to be discussed later is
also of this type, e.g.
•N.CHa
NO
In the same way, in the benzidine reaction, the group HN.C6H6
becomes separated from nitrogen and attaches itself as HaN.C6H4 to
the y-position left free by the hydrogen atom.
187
NH,
Special attention must be drawn to the fact that the radicles which
wander do not do so as " free radicles ", but that the movements of
these groups take place within the range of the molecular forces.
The similarity of the rearrangement of aromatic hydrazo-compounds
to the exchange reactions with which they were compared above becomes
more marked in those cases where the y-positions of the two benzene
nuclei are occupied. Then, as a rule, a diphenyl base is not produced,
but the radicle which separates moves so that its nitrogen atom takes
up the o-position with respect to the other nitrogen atom ; derivatives
of o-aminodiphenylamine are thus produced, e.g.
NH
H3C
This form of the isomerisation is known as the semidine transformation
(P. Jacobson).
Benzidine, and the diphenyl bases tolidine and dianisidine which are
produced in the same way from o-nitrotoluene and o-nitroanisole, are