The same apparatus is employed as in the preparation of dichlorohydrin
(preparation VIII, p. 29).
The portion boiling 120-130'0/14 mm. only amounts to 15-30
g., showing that very little of the b-compound is formed.
This is further shown by the fact that the dichlorohydrin formed
by continued action of hydrogen chloride under the same conditions
contains very little, if any, a, b dichloride.
Two kilograms of concentrated sulfuric acid and 750 g.
of concentrated hydrochloric acid are sufficient to produce
the necessary amount of hydrogen chloride.
A light straw-colored final product is obtained in some cases.
An alternative procedure which is slower and gives slightly
lower yields, but does not require a hydrogen chloride generator,
is as follows:
Three hundred grams of glycerol, 600 cc. of hydrochloric acid
(sp. gr. 1.19) and 15 g. of glacial acetic acid are heated
under a reflux condenser for ten hours, in a 2-l. flask.
The boiling should be very gentle in the early stage of
the reaction, as considerable hydrochloric acid vapor is evolved.
As the reaction progresses, and the evolution of acid vapors diminishes,
the mixture is more strongly heated.
The reaction products are distilled under ordinary pressure until
the temperature of the liquid has reached 140'0 (thermometer bulb
immersed in the liquid). The residual products are distilled
under diminished pressure, and the following fractions obtained.
(1) Up to 115'0/11 mm.; (2) 115-117'0/ 11 mm.; (3) 117-170'0/11 mm.
(1) is mostly aqueous hydrochloric acid; (2) is the monochlorohydrin;
and (3) is glycerol. The second portion is redistilled and the portion
boiling at 115-118'0/11 mm. or 133-136'0/20 mm. is collected.
The yield is 190-205 g., 53-57 per cent of the theoretical amount.