Organic Syntheses, Coll. Vol. 4, p.436 (1963); Vol. 32, p.65 (1952).
Checked by H. R. Snyder and Richard S. Colgrove.
1. Procedure
In a
1-l. round-bottomed flask, bearing an
efficient reflux condenser (Note 1), are placed
286 g. (2 moles) of 2-ethylhexanamide (Note 2),
300 ml. of dry benzene (Note 3), and
357 g. (218 ml., 3 moles) of thionyl chloride (Note 4). The flask is placed in a
water bath, which is heated quickly to 75–80° and maintained at that temperature for 4.5 hours
(Note 5). The reaction mixture is transferred to a
1.5-l. beaker and cooled in an
ice bath. A mixture of 100 g. of crushed ice and 100 ml. of water is added to decompose the excess
thionyl chloride. Cold
50% potassium hydroxide solution is added in small portions, with stirring, until the mixture is alkaline to litmus
(Note 6). The mixture is transferred to a
separatory funnel, and the layers are separated. The aqueous portion is extracted with
100 ml. of benzene. The
benzene solutions are combined and washed once with
150 ml. of 1% sodium carbonate solution and twice with 150-ml. portions of water
(Note 7). The mixture is distilled from a
modified Claisen flask, the bulk of the solvent being removed at atmospheric pressure. The yield of nitrile is
215–236 g. (
86–94%); b.p.
118–120°/100 mm. (Note 8),
(Note 9), and
(Note 10).
2. Notes
1.
Unless the temperature of the water supplied to the condenser is below 20°, a larger amount of
thionyl chloride may be required. The condenser should be attached to a
gas trap.
2.
The
2-ethylhexanamide was prepared in
86–88% yield from
technical 2-ethylhexanoic acid (Carbide and Carbon Chemicals Corporation) by a method similar to that described previously,
2 except that the crude amide was filtered directly from the reaction mixture, washed well with water, and dried. The resulting product, which melted at
99–101°, was used without further purification. If the pure amide is desired, this product may be recrystallized (with
83–90% recovery) from
50% ethanol. For
100 g. of amide,
2 l. of 50% ethanol is used, and the hot solution is decolorized with charcoal. The product thus obtained is in the form of white needles which melt at
102–103°.4.
The submitters used
Eastman Kodak Company white label grade thionyl chloride. The checkers purified
commercial thionyl chloride (Hooker Electrochemical Company, refined grade) by the method of Cottle.
35.
It is advisable to carry out the reaction in a
hood, as
hydrogen chloride and
sulfur dioxide are evolved. The evolution of gases stops just before the end of the specified heating period.
7.
Drying of the solution is unnecessary, since the water present is removed in the next step by azeotropic distillation with
benzene.
8.
The checkers collected the product at
70.5–72°/10 mm.;
nD25 1.4145.
9.
Benzonitrile also can be prepared by this method in comparable yields, but a longer reaction time (7 hours) is required. The method was found to be unsatisfactory for the preparation of the nitriles of azelaic and phthalic acids from the corresponding diamides.
10.
The submitters prepared
palmitonitrile in more than
90% yield by heating the amide with a
benzene solution of
thionyl chloride for 6 hours followed directly by distillation. The nitrile so obtained was contaminated with a product having a strong sulfurous odor which could be removed by washing with aqueous
mercuric acetate. By the described procedure,
palmitonitrile free from objectionable odor was prepared in
80% yield. Troublesome emulsions were formed during the neutralization and washing steps; the addition of a small amount of
ethanol aided in breaking the emulsions.
3. Discussion
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