IN a 5-l. round-bottom flask, fitted with an efficient reflux
condenser of wide bore, are placed, in the following order, 80 g.
of powdered crystalline ferrous sulfate, 865 g. of glycerol
(c. p.), 218 g. of aniline, 170 g. of nitrobenzene, and 400 cc.
of concentrated sulfuric acid (sp. gr. 1.84). The contents of the flask
are well mixed and the mixture heated gently over a free flame.
As soon as the liquid begins to boil, the flame is removed, since the heat
evolved by the reaction is sufficient to keep the mixture boiling
for one-half to one hour. If the reaction proceeds too violently at
the beginning, the reflux condenser may be assisted by placing a wet
towel over the upper part of the flask. When the boiling has ceased
the heat is again applied and the mixture boiled for five hours.
It is then allowed to cool to about 100'0 and transferred to a 12-l. flask;
the 5-l. flask is rinsed out with a small quantity-of water.
The 12-l. flask is then connected with the steam-distillation
apparatus shown in Fig. 3, a 12-l. flask being used as a receiver;
steam is passed in (without external heat) until 1500 cc.
have distilled (ten to thirty minutes). This removes all
the unchanged nitrobenzene (10-20 cc.). The current of steam
is then interrupted, the receiver is changed, and 1500 g.
of 40 per cent sodium hydroxide solution are added cautiously
through the steam inlet. The heat of neutralization is sufficient
to cause the liquids to boil and thus become thoroughly mixed.
Steam is then passed in as rapidly as possible until all the quinoline
has distilled. In this process, 6-8 l. of distillate are collected
(two and a half to three and a half hours are required, unless a
very efficient condensing apparatus is used, under which conditions
the distillation may be complete in one-half to one and a half hours).
The distillate is allowed to cool, and the crude quinoline separated.
The aqueous layer of the distillate is again distilled with steam
until all the quinoline has been volatilized and collected in about
3 l. of distillate.
These 3 l. of distillate are then mixed with the first yield of quinoline
and 280 g. (150 cc.) of concentrated sulfuric acid are added.
The solution is cooled to 0-5'0, and a saturated solution of sodium
nitrite added until a distinct excess of nitrous acid is present
(as shown either by starch-potassium iodide paper or by the odor).
This generally requires 50 to 70 g. of sodium nitrite.
The mixture is then warmed on a steam bath for an hour, or until
active evolution of gas ceases, and is then distilled with steam
until all the volatile material has been expelled (41. of distillate
will result) The receiver is then changed and the mixture in
the distillation flask is neutralized, as before, with 700 g.
of 40 per cent sodium hydroxide solution. The quinoline is distilled
exactly as described above, the aqueous portions of the distillate
being distilled with steam until all the quinoline has been isolated.
The crude product is then distilled under reduced pressure,
and the fraction which boils at 110-114'0/14 mm. is collected.
The foreruns are separated from any water which may be present, dried with
a little solid alkali, and redistilled. The total yield is 255-275 g.
(84-91 per cent of the theoretical amount based on the aniline taken).