2.NHR, may be prepared by the
action of the primary and secondary amines on the diazonium salts, or
by the action of nitrous acid on the free primary amine. In the latter
reaction it is assumed that the isodiazohydroxide first formed is
immediately attacked by a second molecule of the amine. They are
yellow crystalline solids, which do not unite with acids. Nitrous acid
converts them, in acid solution, into diazonium salts.

C6H5N2.NHC6H5 + 2HCl + HNO2 = 2C6H5N2Cl + 2H2O.

They are readily converted into the isomeric aminoazo compounds,
either by standing in alcoholic solution, or by warming with a mixture
of the parent base and its hydrochloride; the diazo group preferably
going into the para-position to the amino group. When the
para-position is occupied, the diazo group takes the ortho-position.
H. Goldschmidt and R. U. Reinders (_Ber._, 1896, 29, p. 1369, 1899)
have shown that the transformation is a monomolecular reaction, the
velocity of transformation in moderately dilute solution being
independent of the concentration, but proportional to the amount of
the catalyst present (amine hydrochloride) and to the temperature. It
has also been shown that when different salts of the amine are used,
their catalytic influence varies in amount and is almost proportional
to their degree of ionization in aqueous solution. Diazoaminobenzene,
C6H5N2.NHC6H5, crystallizes in golden yellow laminae, which melt at
96 deg. C. and explode at a slightly higher temperature. It is readily
soluble in alcohol, ether and benzene. Concentrated hydrochloric acid
converts it into chlorbenzene, aniline and nitrogen. Zinc dust and
alcoholic acetic acid reduce it to aniline and phenylhydrazine.

_Diazoimino compounds_, R.N3, may be regarded as derivatives of
azoimide (q.v.); they are formed by the action of ammonia on the
diazoperbromides, or by the action of hydroxylamine on the diazonium
sulphates (J. Mai, _Ber._, 1892, 25, p. 372; T. Curtius, _Ber._, 1893,
26, p. 1271). Diazobenzeneimide, C6H5N3, is a yellowish oil of
stupefying odour. It boils at 59 deg. C. (12 mm.), and explodes when
heated. Concentrated hydrochloric acid decomposes it with formation of
chloranilines and elimination of nitrogen, whilst on boiling with
sulphuric acid it is converted into aminophenols.

_Aliphatic Diazo Compounds._--The esters of the aliphatic amino acids
may be diazotized in a manner