similar to the primary aromatic amines,
a fact discovered by T. Curtius (_Ber._, 1833, 16, p. 2230). The first
aliphatic diazo compound to be isolated was _diazoacetic ester_,
CH.N2.CO2C2H5, which is prepared by the action of potassium nitrite on
the ethyl ester of glycocoll hydrochloride, HCl.NH2.CH2.CO2C2H5 + KNO2
= CHN2.CO2C2H5 + KCl + 2H2O. It is a yellowish oil which melts at -24
deg. C.; it boils at 143-144 deg. C., but cannot be distilled safely
as it decomposes violently, giving nitrogen and ethyl fumarate. It
explodes in contact with concentrated sulphuric acid. On reduction it
yields ammonia and glycocoll (aminoacetic acid). When heated with
water it forms ethyl hydroxy-acetate; with alcohol it yields ethyl
ethoxyacetate. Halogen acids convert it into monohalogen fatty acids,
and the halogens themselves convert it into dihalogen fatty acids. It
unites with aldehydes to form esters of ketonic acids, and with
aniline yields anilido-acetic acid. It forms an addition product with
acrylic ester, which on heating loses nitrogen and leaves trimethylene
dicarboxylic ester. Concentrated ammonia converts it into
_diazoacetamide_, CHN2.CONH2, which crystallizes in golden yellow
plates which melt at 114 deg. C. For other reactions see HYDRAZINE.
The constitution of the diazo fatty esters is inferred from the fact
that the two nitrogen atoms, when split off, are replaced by two
monovalent elements or groups, thus leading to the formula

N \
.. > CH.CO2C2H5, for diazoacetic ester.
N /

_Diazosuccinic ester_, N2.C(CO2C2H5)2, is similarly prepared by the
action of nitrous acid on the hydrochloride of aspartic ester. It is
decomposed by boiling water and yields fumaric ester.

_Diazomethane_, CH2N2, was first obtained in 1894 by H. v. Pechmann
(_Ber._, 1894, 27, p. 1888; 1895, 28, p. 855). It is prepared by the
action of aqueous or alcoholic solutions of the caustic alkalis on the
nitroso-acidyl derivatives of methylamine (such, for example, as
_nitrosomethyl urethane_, NO.N(CH3).CO2C2H5, which is formed on
passing nitrous fumes into an ethereal solution of methyl urethane).
E. Bamberger (_Ber._, 1895, 28, p. 1682) regards it as the anhydride
of iso-diazomethane, CH3.N:N.OH, and has prepared it by a method
similar to that used for the preparation of iso-diazobenzene. By the
action of bleaching powder on methylamine hydrochloride, there is