Org. Synth. 1945, 25, 95
DOI: 10.15227/orgsyn.025.0095
SEBACONITRILE AND ω-CYANOPELARGONIC ACID
[Sebaconitrile and pelargonic acid, θ-cyano-]
Submitted by B. S. Biggs and W. S. Bishop.
Checked by C. F. H. Allen and J. VanAllan.
1. Procedure
A. Sebaconitrile. A 3-l. three-necked flask (Note 1), equipped with a mechanical stirrer (Note 2) and (Note 3) and a thermometer which dips into the liquid, is heated in an oil bath to 160°. In the flask are placed 505 g. (2.5 moles) of commercial sebacic acid (Note 4) and 180 g. (3 moles) of urea (Note 5), and the melt is heated with stirring for 4 hours at about 160° (Note 6). The oil bath is removed, the surplus oil is wiped off, the flask is insulated (Note 7), and the temperature is then raised, as rapidly as foaming permits, to 220° by means of a triple burner and wire gauze. It is important to continue the stirring for at least 5 minutes after 220° is attained; otherwise the mass will foam over during the subsequent distillation.
The stirrer is then replaced by a short still head connected to a long (90-cm.) air condenser and receiver (Note 8), and the product is distilled at atmospheric pressure as long as any distillate is obtained. The temperature of the vapor rises gradually to 340°. The distillate, which consists chiefly of water, dinitrile, acid nitrile, and sebacic acid, is poured into a large (2-l.) separatory funnel and, after the addition of 500 ml. of ether (Note 9), is extracted three times with 650-ml. portions of 5% ammonium carbonate (Note 10). The crude dinitrile which remains after the removal of the ether is distilled under reduced pressure; after a small fore-run (20–25 ml.) the main product is collected at 185–188°/12 mm. (Note 11). The yield of sebaconitrile is 190–200 g. (46–49%) (Note 12).
B. ω-Cyanopelargonic acid. The combined ammoniacal extracts are heated nearly to boiling in a large enameled pot or 4-l. beaker and neutralized to phenolphthalein with concentrated hydrochloric acid (about 120 ml.) (Note 13). A hot solution of 400 g. of barium chloride is then added slowly with stirring, and the hot solution is filtered from the precipitated barium sebacate (Note 14) through a fluted filter paper or "Shark Skin" filter paper (Note 15) on a 20-cm. Büchner funnel. The barium salt of the cyano acid that separates on cooling is filtered on the same sized funnel and dissolved in 1 l. of hot water, and the solution is acidified to litmus with concentrated hydrochloric acid (about 30 ml.). The cyano acid separates as a clear oil. The filtrate from which the barium salt was filtered is acidified likewise to litmus with concentrated hydrochloric acid (about 50 ml.). The two oils are combined. The cyano acid is washed by decantation with three 200-ml. portions of hot water, separated completely from water, and dried in a vacuum desiccator over calcium chloride. The yield of ω-cyanopelargonic acid melting at 48–49° is 146–155 g. (32–34%) (Note 16).
2. Notes
1.
Ground-glass equipment is preferable, since the final temperature is high enough to decompose
rubber or cork stoppers.
2.
The stirrer is a bent glass rod that will break up the foam produced.
3.
Attention is called to the powerful but compact compressed-air stirrer, catalog No. 9224, of the A. H. Thomas Company. When a compressed-air line is available, such a stirrer is preferable to an electric motor.
4.
Commercial grades of sebacic acid (m.p.
127–130°) and
urea (m.p.
132–134°) were used; pure
sebacic acid (m.p.
132–133°) gives only a slightly (13%) higher yield. Since the acid is light and bulky, it is convenient to melt it in an enameled pot
(p. 614, Note 2) and pour the liquid into the preheated flask.
5.
It is important to use the amount of
urea which is specified. When
2 moles of urea per mole of sebacic acid was employed, the yield of
sebaconitrile was only
27%.
6.
At the end of this time the product consists almost entirely of
sebacamide, which may be isolated if desired.
7.
This insulation is easily accomplished by wrapping with asbestos rope, starting at the neck and winding as far down the bulge of the flask as possible. After the flask is clamped in place on the wire gauze, asbestos paper is bent around to enclose the bottom. Magnesia can also be used.
8.
If the condenser is short, it is advisable to have a second receiver with a
reflux condenser attached, because some dinitrile may be carried through by uncondensed steam. A
water-cooled condenser should not be placed ahead of the first receiver, however, since the distillate contains some solid products (
sebacic acid and products from
urea).
9.
Although not absolutely essential, the
ether facilitates the operation.
Benzene is not satisfactory.
10.
Ammonium hydroxide (about 3%) is equally satisfactory. The aqueous extracts are saved.
11.
Another boiling point is
201–203°/16 mm.12.
The submitters obtained
410–450 g. (
50–55%) in runs twice this size.
13.
The checkers used a
pH meter and neutralized to
pH 7.8.
14.
This amounts to 43–45 g.
15.
S & S "Shark Skin" filter paper has "high wet-strength" and a high resistance to acids and alkalies.
16.
If the cyano acid obtained from the precipitated barium salt is worked up separately, it melts at 51–52°.
3. Discussion
Sebaconitrile has been obtained by heating
sebacic acid in a stream of
ammonia,
1 and from
sebacamide by pyrolysis
2,3 or by dehydration with
phosphorus pentachloride4 or
phosphorus oxychloride.
5 Sebacamide has been prepared from
ethyl sebacate,
6,7 sebacoyl chloride,
7 or
polysebacic anhydride8 and
ammonia; by heating
sebacic acid with
urea2,3,9 or
ammonium thiocyanate;
10 and by the electrolysis of
adipic acid monoamide.
11
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
pelargonic acid, θ-cyano-
polysebacic anhydride
calcium chloride (10043-52-4)
hydrochloric acid (7647-01-0)
ammonium carbonate (506-87-6)
ammonia (7664-41-7)
Benzene (71-43-2)
ether (60-29-7)
ammonium thiocyanate (1762-95-4)
phosphorus pentachloride (10026-13-8)
barium chloride (10361-37-2)
Phosphorus Oxychloride (21295-50-1)
urea (57-13-6)
ammonium hydroxide (1336-21-6)
phenolphthalein (77-09-8)
Ethyl sebacate (693-55-0)
sebacamide (1740-54-1)
sebacic acid (111-20-6)
Sebaconitrile (1871-96-1)
ω-CYANOPELARGONIC ACID (5810-19-5)
barium sebacate
adipic acid monoamide
sebacoyl chloride (111-19-3)
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