Org. Synth. 1931, 11, 54
DOI: 10.15227/orgsyn.011.0054
[Enanthaldehyde oxime]
Submitted by E. W. Bousquet
Checked by W. H. Carothers and W. L. McEwen.
1. Procedure
In a 5-l. two-necked flask, fitted with a mechanical stirrer, a reflux condenser, a thermometer, and a separatory funnel, are placed an aqueous solution of 348 g. (5 moles) of hydroxylamine hydrochloride (Org. Syn. Coll. Vol. I, 1941, 318) in 600 cc. of cold water and 460 g. (4 moles) of heptaldehyde (Note 1). Stirring (Note 2) is started, and a solution of 265 g. (2.5 moles) of anhydrous c.p. sodium carbonate in 500 cc. of water is added at such a rate that the temperature of the reaction mixture does not rise above 45°. Stirring is continued at room temperature for an hour after the addition of the sodium carbonate solution is complete.
The oily layer on top of the reaction mixture is separated and washed with two 100-cc. portions of water (Note 3). The washed product is transferred to a 1.5-l. modified Claisen flask and distilled under reduced pressure from an oil bath. The first fraction contains a very small amount of water along with a mixture of heptanonitrile and heptaldoxime. The product is collected at 103–107°/6 mm. (temperature of the oil bath, 140–147°) (Note 4). The yield is 420–480 g. (81–93 per cent of the theoretical amount). The product solidifies slowly on cooling and melts at 44–46°. It can be used for reduction to n-heptylamine (p. 318) without further purification.
The product can be purified by recrystallization from 60 per cent ethyl alcohol, using approximately 70 cc. of the solvent to 25 g. of the distilled product. One such recrystallization (Note 5) gives white leaflets melting at 53–55° (Note 6) and (Note 7). The yield of recrystallized material from a single run is 315–320 g.
2. Notes
1. The heptaldehyde used boiled at 54–59°/16 mm.
2. Since the heptaldehyde and the aqueous solution of hydroxylamine hydrochloride form a heterogeneous mixture, it is necessary to provide rapid, efficient stirring in order to obtain good results.
Ethyl alcohol can be used to provide a homogeneous solution, but the yield seems to be diminished slightly owing to the presence of more high-boiling material.
3. The product is so insoluble in water that an ether extraction is hardly necessary to obtain all the product from the water solution if sufficient time is allowed for the separation of the two layers.
4. The temperature of the oil bath during distillation is important. The first fraction is cut as soon as a constant boiling point is reached, and this constancy of boiling point is obtained sooner if the temperature of the oil bath is regulated to a constant temperature before distillation is started. No more than 50 cc. (of which approximately 10 cc. is water) should come over in the first fraction. If the temperature of the bath is regulated carefully, practically all the product will distil at a constant temperature.
5. The product is dissolved by gentle heating and the solution is then cooled to 0° or below for several hours. The material remaining in the mother liquor (about 30 per cent of the total) may be recovered as impure, oily oxime by evaporation of the alcohol.
6. The melting point given was determined by the capillary-tube method and depended on the rate of heating. The melting point as given in the literature varies from 50° to 58°.
7. Cyclohexanone oxime can be prepared in the same percentage yields by a procedure which differs from the above only in that the reaction mixture becomes solid before the addition of the sodium carbonate is complete. After all the sodium carbonate has been added, steam is passed in until the oxime is melted, and the mixture is shaken vigorously for fifteen minutes at five-minutes intervals. Cyclohexanone oxime boils at 100–105°/10–12 mm. and melts at 87–88°.
3. Discussion
Heptaldoxime has been prepared only by the action of the aldehyde on an aqueous solution of hydroxylamine hydrochloride in the presence of alkali;1 the method described above is a modification of that given by Westenberger.1

References and Notes
  1. Westenberger, Ber. 16, 2992 (1883); Goldschmidt and Zanoli, ibid. 25, 2593 (1892); Bourgeois and Dambmann, ibid. 26, 2860 (1893).

Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)


ethyl alcohol (64-17-5)

sodium carbonate (497-19-8)

Hydroxylamine hydrochloride (5470-11-1)

Cyclohexanone oxime (100-64-1)

Enanthaldehyde oxime (629-31-2)

heptanonitrile (629-08-3)

heptaldehyde (111-71-7)

n-heptylamine (111-68-2)