Quinoline has been produced by passing the vapor of allylaniline
over red-hot lead oxide;[1a] by heating acrylideneaniline, or better,
a mixture of aniline, glycerol and sulfuric acid;[2a] by heating
aniline with glycerol and sulfuric acid, using nitrobenzene as an
oxidizing agent;[1] by treating a mixture of glyoxal and _o_-toluidine
with alkali;[2] by treating a solution of _o_-aminobenzaldehyde with
acetaldehyde and alkali;[3] by heating methylacetanilide with zinc
chloride;[4] by heating aminoazobenzene with glycerol and sulfuric
acid;[5] by heating a mixture of aniline, glycerol and sulfuric
acid with arsenic acid.[6]
[1a] Ber. 12, 453 (1879).
[2a] Ber. 13, 911 (1880); Monatsh. 1, 316 (1880).
[1] Monatsh. 2, 141 (1881); J. prakt. Chem. (2) 49, 549 (1894),
[2] Monatsh. 15, 277 (1894).
[3] Ber. 15, 2574 (1882); 16, 1833 (1883).
[4] Ber. 23, 1903 (1890).
[5] Ber. 24, 2623 (1891)
[6] Ber. 29, 704 (1896)
Of the above methods, the only ones which need be considered are
those in which a mixture of aniline, glycerol and sulfuric acid
is heated with an oxidizing agent. With the use of nitrobenzene,
the reaction, according to the original method, takes place
with extreme violence.
The method above described is the most satisfactory for the preparation
of quinoline itself, but for the preparation of homologues
of quinoline, the use of arsenic acid is preferable, since the yields
are somewhat greater.
Since the work was carried out, a method has been published[7] in
which aniline, glycerol and sulfuric acid are treated with ferric oxide.
By this method Adams and Parks were unable to obtain yields comparable
with those resulting from the above directions.
[7] Chem. News 121, 205 (1920).