A given nitrogen-containing aromatic compound A
reacts with Sn/HCl, followed by ``HNO_2`` to give an
unstable compound B. B, on treatment with phenol,
forms a beatiful coloured compound C with the
molecular formula ``C_{12}H_{10}N_2O``.
The structure of compound A is :-
(1)
(2)
(3)
(4)