Laboratory Methods of Organic Chemistry - Sciencemadness Dot Org

GLYCINE BSTBK HYDKOCHLOKIDB 275
The azo-compound corresponding to azobenzene, azomeihane
CH3.N=N.CH3, is a colourless explosive gas (at low temperatures a
pale yellow liquid) obtained by dehydrogenation of the corresponding
hydrazine (hydrazomethane) (Thiele, Ber., 1909, 42, 2575).
For further reactions of the aliphatic diazo-compounds see ethyl
diazoacetate (below).
2. ETHYL DIAZOACETATE
(a) Glycine Ethyl Ester Hydrochloride, 1 H5C2OOC.CH2NH2.HCL—
Chloroacetic acid (94 g.; 1 mole) dissolved in 30 c.c. of water is run,
at 15°, with shaking into a litre of concentrated ammonia (d. 0-913).
The flask is stoppered and left for twenty-four hours. Then the
liquid is heated in a basin on a ring burner (fume chamber !) until
the large excess of ammonia has evaporated and its odour is hardly
perceptible. Concentrated hydrochloric acid (100 c.c.) is next added
to make the solution distinctly acid to Congo paper, and heating is
continued over an open flame, with continuous stirring, until a sample
of the pale yellow material, which is semi-solid while hot, becomes
completely hard on cooling. At this stage overheating must be
avoided by lowering the flame and stirring very vigorously.
While the hot mass is cooling it is thoroughly ground in a porcelain
mortar, and before the subsequent esterification the water which is
still present is removed by transferring the powdered mixture of
ammonium chloride and glycine hydrochloride to a short-necked,
round-bottomed flask which is suspended in a boiling water bath and
evacuated with a pump. After four hours the mass is again powdered
and the heating in vacuo is continued for three hours, this time in an
oil bath at 115°. The salt mixture, 2 which is now in the form of a dry
dust, is at once transferred to a double-necked round-bottomed flask
connected by means of ground glass connexions to a reflux condenser
and a gas delivery tube (Fig. 47, p. 104) and boiled with 350 c.c. of
absolute alcohol, whilst a strong current of dry hydrogen chloride is
passed into the boiling mixture until thick fumes escape from the
condenser. (Because of the " bumping " which occurs during boiling
the ring of the water bath on which the flask stands is wrapped in a
towel.) The hydrogen chloride apparatus is now disconnected and
boiling is continued for one hour. By filtration at the pump the
ammonium chloride is separated from the hot liquid and is washed
1 Hantzsch and Silberrad, Ber., 1900, 33, 70.
2 A few grammes of the salt mixture are laid aside for the preparation of hippuric
acid as described below.