Org. Synth. 1945, 25, 61
DOI: 10.15227/orgsyn.025.0061
ISOBUTYRONITRILE
Submitted by R. E. Kent and S. M. McElvain.
Checked by C. R. Noller and D. Frazier.
1. Procedure
To 308 g. (2.1 moles) of phosphorus pentoxide (reagent grade) in a 3-l. round-bottomed flask is added 174 g. (2 moles) of finely powdered, dry isobutyramide (Note 1). The flask is tightly stoppered, and the two dry solids are thoroughly mixed by shaking. The flask then is attached to a water-cooled condenser set for downward distillation; a 500-ml. suction flask connected to the condenser by a rubber stopper is a convenient receiver. A calcium chloride tube is attached to the side arm of the receiver, and the receiver is surrounded by crushed ice. The reaction flask is heated for 8–10 hours in an electrically heated oil bath maintained at 200–220°. The nitrile starts to distil almost at once. The reaction mixture becomes a thick, brown syrup which foams considerably toward the end of the distillation. The time of reaction may be cut to 1–2 hours by connecting the distillation system to an aspirator and intermittently removing the nitrile under reduced pressure (Note 2). Very little additional nitrile can be obtained by further heating of the reaction mixture.
The contents of the receiver are transferred to a 500-ml. modified Claisen flask, 10–15 g. of phosphorus pentoxide is added (Note 3), and the product is distilled from an oil bath held at 145–155°. After only a few drops of fore-run, the main fraction distils at 99–102°/740 mm. The yield is 96–120 g. (69–86%). The product is colorless when first distilled but acquires a yellow tint after standing a few days. If it is again distilled from phosphorus pentoxide or Drierite, it boils at 101–103° and remains colorless; n25D 1.3713.
2. Notes
1.
The amide must be thoroughly dry or immediate reaction will take place with considerable generation of heat, and the yield will be lowered owing to the failure to obtain proper mixing of the reactants. If the amide is not finely powdered the yield of nitrile falls off sharply.
2.
The yield is not altered by this procedure if care is taken not to evaporate the nitrile in the receiver. Keeping the flask surrounded by crushed ice and using a
Dry Ice-acetone safety trap between the receiver and
aspirator will guard against such loss.
3.
When
phosphorus pentoxide is added to
isobutyronitrile, the liquid sets to a semisolid gel which is difficult to transfer from a flask. Hence, the addition of one to the other should be made only in the flask from which the distillation is to be made.
3. Discussion
Isobutyronitrile has been prepared by a number of catalytic vapor-phase reactions at elevated temperatures:
isobutylamine over
copper1 or
nickel,
2 isobutyramide over
alumina,
3 a mixture of
ammonia and isobutyraldehyde over
thorium dioxide4 or other catalysts,
5 a mixture of
ammonia and isobutyl alcohol over
copper,
6 and a mixture of
isobutylene oxide and ammonia over
alumina and
copper.
7 It has also been prepared by decarboxylation of
2-methyl-2-cyanopropanoic acid,
8 and by the reaction of
isobutyric acid with
potassium thiocyanate.
9 The above procedure is a modification of the method used by Walter and McElvain.
10
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
alumina
Drierite
ammonia (7664-41-7)
thorium dioxide
copper (7440-50-8)
nickel (7440-02-0)
potassium thiocyanate (333-20-0)
isobutyl alcohol (78-83-1)
isobutyraldehyde (78-84-2)
Isobutyramide (563-83-7)
isobutyric acid (79-31-2)
Isobutyronitrile (78-82-0)
isobutylamine (78-81-9)
isobutylene oxide (558-30-5)
2-methyl-2-cyanopropanoic acid
phosphorus pentoxide (1314-56-3)
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