o a certain amount of the sodium salt (A. Hantzsch,
_Ber._, 1898, 31, p. 1612),

....
C6H5.N.:OH: --> C6H5.N --> C6H5.N
| : : || ||
HO.N.:H : <-- HO.N <-- NaO.N
....

This assumption also shows the relationship of the diazonium
hydroxides to other quaternary ammonium compounds, for most of the
quaternary ammonium hydroxides (except such as have the nitrogen atom
attached to four saturated hydrocarbon radicals) are unstable, and
readily pass over into compounds in which the hydroxyl group is no
longer attached to the amine nitrogen; thus the syn-diazo hydroxides
are to be regarded as pseudo-diazonium derivatives. (A. Hantzsch,
_Ber._, 1899, 32, p. 3109; 1900, 33, p. 278.) It is generally accepted
that the iso-diazo hydroxides possess the oxime structure R.N:N.OH.

Hantzsch explains the characteristic reactions of the diazonium
compounds by the assumption that an addition compound is first formed,
which breaks down with the elimination of the hydride of the acid
radical, and the formation of an unstable syn-diazo compound, which,
in its turn, decomposes with evolution of nitrogen (_Ber._, 1897, 30,
p. 2548; 1898, 31, p. 2053).

R X R X R X
\ | \ / | |
N.:N + | --> N.:N --> | | + HCl --> R.X + N2.
/ | / \ | |
Cl H Cl H N = N

J. Cain (_Jour. Chem. Soc._, 1907, 91, p. 1049) suggested a quinonoid
formula for diazonium salts, which has been combated by Hantzsch
(_Ber._, 1908, 41, pp. 3532 et seq.). G. T. Morgan and F. M. G.
Micklethwaite (_Jour. Chem. Soc._, 1908, 93, p. 617; 1909, 95, p.
1319) have pointed out that the salts may possess a dynamic formula,
Cain's representing the middle stage, thus:

/||\ /||\ /||\
/ || \ / || \ / || \
H / N.Cl \ H H / N.Cl \ H H / N.Cl \ H
|\ || || ---> || || | ---> || || /|
| \ || || <--- || || | <--- || || / |
| \N || || N | || N |
H\\ / H H\\ | / H H \ //H
\\ / \\ | / \ //
\\ / \\| / \ //
H H H

_Diazoamines._--The diazoamines, R.N