B.
Isobutyramide. In a
3-l. flask, equipped with an efficient stirrer and a
500-ml. dropping funnel, and surrounded by an ice-salt freezing mixture, is placed
1.25 l. of cold concentrated aqueous ammonia (about 28%). To this
318 g. (3 moles) of isobutyryl chloride is added dropwise with rapid stirring at such a rate that the temperature of the reaction mixture does not rise above 15°, and the evolution of white fumes (mostly
ammonium chloride) does not become vigorous. Stirring is continued for 1 hour after the addition of the acid chloride is finished.
The flask is heated by steam in a large can, and the reaction mixture is evaporated to dryness under reduced pressure (Note
6). The dry residue of
ammonium chloride and
isobutyramide is boiled 10 minutes with
2 l. of dry ethyl acetate, and the boiling solution is filtered quickly through a fluted filter paper on a
large hot funnel. The residue on the filter is extracted in the same way with two
1-l. portions of ethyl acetate. The combined
ethyl acetate extracts are cooled to 0°, and the crystalline amide which separates is removed by filtration. The filtrate is concentrated to about 300 ml. and chilled, and a second crop of amide is collected (Note
7) and (Note
8). The two crops of
isobutyramide are combined and dried, first in an
oven at 70° for 3 hours and then in a
vacuum desiccator. The yield of glistening white needles melting at
127–129° is
203–215 g. (
78–83%) (Note
9). This material is suitable for the preparation of
isobutyronitrile.