Laboratory Methods of Organic Chemistry - Sciencemadness Dot Org

KEACTIONS OF ANILINE 167
three drops of aniline with 10 c.c. of water in a test tube) are diluted
with 100 c.c. of water and a small quantity of a filtered aqueous
solution of bleaching powder is added. A violet colour is thus produced
(Eunge's reaction). This very sensitive reaction is given only
by aqueous solutions oifree aniline and not by those of its salts, from
which it must first be isolated.
The reaction may also be used to detect small quantities of
benzene or of nitrobenzene, after these have been converted in the
manner just described, by reactions carried out in a test tube.
The bleaching powder reaction is peculiar to aniline; the dye
which is formed is a complex quinone derivative the constitution of
which is not yet known with complete certainty. The other experiments,
about to be described, are group reactions for primary aromatic
amines.
2. Primary and secondary amines are acylated by acid chlorides
and anhydrides, in particular also by the chloride of benzene sulphonic
acid (p. 192). The preparation of acetanilide has already been described
(pp. 125, 128). The acetyl- and benzoyl-derivatives of all the
simpler primary amines of the benzene and naphthalene series are known,
so that these derivatives can always serve for purposes of identification.
As an exercise a primary amine should be identified in the manner
described.
3. Benzylidene-aniline.—Aniline (1 c.c.) is heated in a test tube
on the water bath with an equal quantity of benzaldehyde. The
mixture becomes turbid because water separates. On cooling a
solid is formed, a so-called SchifE's base (azomethine). Melting
point 72°.
This feebly basic condensation product is decomposed into its components
when warmed with acid. The reaction is a general one for
primary amines.
4. Isonitrile Reaction.—Like the primary aliphatic amines of the
methylamine type, aniline and its analogues give a characteristic odour
with chloroform and alkali.
Aniline (2 drops) and alcohol (2 c.c.) are mixed in a test tube
and 0-5 c.c. of concentrated potassium hydroxide solution along with
about five drops of chloroform are added. The mixture is then
gently warmed in a fume chamber.
n.
C6H5.NH2 + C12C< +3K0H = C6H5.N: