Laboratory Methods of Organic Chemistry - Sciencemadness Dot Org

252 ACBTYLACBTONB
moderate vigour only, until all the sodium has dissolved; about
three hours are required. The yield is reduced if boiling is continued
too long. The process is brought to an end as soon as possible and
any small residue of sodium is neglected. The warm liquid is shaken
with a mixture of 70 c.c. of glacial acetic acid and 80 c.c. of water
until it is just acid. An equal volume of cold saturated sodium
chloride solution is then added and the lower aqueous layer is separated
in a tap funnel from the upper layer, which consists of ethyl
acetate and ethyl acetoacetate. The mixture of esters is shaken
with a little cold saturated bicarbonate solution,which is then poured
away, and the excess ethyl acetate is now removed by distillation
from a flask connected to a downward condenser and fitted with a
thermometer. A smoky flame is used without wire gauze. As soon
as the temperature reaches 95° heating is stopped and the material
which remains in the flask is distilled in a vacuum through a small
water-cooled condenser (preferably) into the type of receiver shown
in Fig. 16 or 17. If the pressure is below 16 mm. the flask is heated
on the water bath, otherwise an oil or paraffin bath is used. After
small amounts of ethyl acetate and water have passed over, the
temperature soon becomes constant and the bulk of the ethyl acetoacetate
distils within one degree. Boiling points at various pressures
: 71°/l2-5 mm., 74°/l4 mm., 79°/18 mm., 88°/29 mm., 94°/45
mm., 97°/59 mm., 100°/80 mm. The yield amounts to 55 to 60 g. of
ethyl acetoacetate. In the flask a substance which crystallises on
cooling remains. It is dehydracetic acid. What is the formula?
The various stages of the experiment should be carried out without
any long interruption, because otherwise the yield suffers.
6. ACETYLACETONE l
Finely powdered sodamide (34 g.), 2 which is kept in a closed container,
is added gradually in small portions to a mixture of 120 c.c. of
ethyl acetate (purified as for the preparation of ethyl acetoacetate)
and 32 c.c. of dry acetone. During the addition of the sodamide the
mixture is cooled in a freezing mixture. The flask is provided with
a cork or rubber stopper carrying a calcium chloride tube. A
vigorous evolution of ammonia at once begins. After all the soda-
1 L. Claiaen, Ber., 1905, 38, 695.
2 The powdering should be carried out as rapidly as possible, preferably in a
metal mortar (goggles to be worn). The yield is determined by the quality of the
sodamide.