208 ESTERS.
mass action. This law requires that at a constant temperature the relation
expressed in the following equation shall hold true:[Ester]. [Water] _
[Acid] • [Alcohol] ~
It is evident from this equation that to obtain a favorable yield of ester the
concentration of the water should be kept as low as possible. This can be
accomplished in practice by adding concentrated sulphuric acid to the reac-
tion mixture. On the other hand, saponification is favored by the removal
of the acid, and this can be brought about by the addition of a base.- Ethyl Nitrate, C 2 H 5 ONO 2.
Ethyl nitrate is formed from nitric acid and ethyl alcohol according to
Method 1 described above. Since, however, the nitric acid may also act as
an oxidizing agent upon the alcohol, and since, moreover, the oxidation is so
vigorously catalyzed by the lower oxides of nitrogen that the mixture some-
times decomposes explosively, the expedient is adopted of adding urea, which
removes the reduction products of nitric acid. Urea reacts with nitrous acid
according to the equation
CO(NH 2 ) 2 + 2 HN0 2 = CO 2 + 2 N 2 + 3 H 2 O.Place in a 150-c.c. distilling flask 38 g. of absolute alcohol, 6 g.
of urea, and 60 g. of concentrated nitric acid (sp. gr. 1.4) which
has previously been boiled with 0.5 g. of urea. Distil the mixture
on the water-bath, and when about one-third has passed over, add
slowly from a dropping funnel a further mixture of 100 g. of con-
centrated nitric acid (which has likewise been boiled with a gram
of urea and subsequently cooled to the room temperature) and
75 g. of absolute alcohol. Continue the distillation until nothing
more passes over. Purify the ester from acid and alcohol by
shaking it three times with water in a separatory funnel, using a
double volume of water for the first shaking. Free'the layer of
ester as completely as possible from drops of water by pouring
it into a dry flask, and let it dry by standing several hours in
contact with granular calcium chloride. Finally, distil the prod-
uct with the bulb of the flask immersed in a water-bath. Yield,
about 40 g. of a colorless liquid which boils sharply at 87°. On
setting fire to a few drops of the ethyl nitrate, it burns with a
pale flame.
By allowing larger amounts of the above mixture to drop into
the reaction flask, the ester may be prepared conveniently in con-siderable quantity.