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12. 2,4,6-Triethylbenzaldehyde and 2,4,6-triisopropylbenzal-dehyde may be prepared in yields of 69 and 65 per cent, respec-
3Fieser, “Experiments in Organic Chemistry,” p. 311, New York, 1941. Reprinted by special permission of D. C. Heath and Company.
tively, by the procedure described above, with a reaction time of eight hours and the following modifications:
Hydrocarbon 100 g. (0.62 mole) 100 g. (0.49 mole)
Zinc cyanide 115 g. (0.97 mole) 102 g. (0.74 mole)
Aluminum chloride 215 g. (1.60 moles) 134 g. (1.0 mole)
Boiling point 146-149°/21 mm. 123-126°/4 mm.
3. Methods of Preparation
Most of the methods for preparing mesitaldehyde have been given previously.4 The procedure described here has been recently published.6' ••7
p-METHYLGLUTARIC ACID (Glutaric acid, p-methyl-)
2CNCH2CONH2 + CH3CHO -» CH3CH[CH(CN)CONH2]2 + H2O CH3CH[CH(CN)CONH2]2 + 6H20 + 4HC1 -» H02CCH2CH(CH3)CH2C02H + 4NH4CI + 2C02
Submitted by Robert E. Kent and S. M. McElvain. Checked by Lee Irvin Smith and G. A. Boyack.
(A) a,a -Dicyano-fi-methylglutaramide.—In a 6-1. flask, 520 g. (6.2 moles) of recrystallized cyanoacetamide (Org. Syn. Coll. Vol. 1, 1941, 179) (Note 1) is dissolved in 3.41. of water, and the solution is cooled to 10° and filtered if it is not clear (Note 2). While the
4 Barnes, Org. Syn. 21, 110.
1 Fuson, Horning, Ward, Rowland, and Marsh, J. Am. Chem. Soc. 64,31 (1942).
* Hinkel, Ayling, and Morgan, J. Chem. Soc. 1932, 2797.
7 Hinkel, Ayling, and Beynon, J. Chem. Soc. 1936, 342.
flask is shaken constantly, 137.5 g. (3.1 moles) of freshly distilled acetaldehyde and 20 cc. of piperidine are added successively to the solution. After the mixture has stood at room temperature for two hours, the flask is transferred to an ice-salt bath and the mixture is partially frozen. During this operation, the flask should be shaken frequently. After thirty minutes, a,c/-dicyano-/Ç-methylglutaramide begins to deposit, and when the precipitation is complete (about one hour), the mixture is allowed to come, to room temperature in order to melt the ice which is present. The precipitate is then filtered with suction and washed thoroughly with cold distilled water. The yield is 420-425 g. (71 per cent of the theoretical amount) of a white, powdery solid which melts at 152-157° (Note 3).
(.Â) /3-Ìelhylglularic Acid.—In a 54. flask are placed 400 g. of the amide and 11. of concentrated hydrochloric acid; the mixture is warmed on a steam bath until solution is complete, after which it is diluted with 1 1. of water and refluxed for eight hours. The amber-colored solution is saturated with sodium chloride and extracted with five 600-cc. portions of ether. The combined ether extracts are dried for one hour over phosphorus pentoxide, and the solvent is removed by distillation. The residue, crude (3-methylglutaric acid, weighs 238-240 g. (80 per cent of the theoretical amount) and melts at 79-82° with previous softening. This product is recrystallized from about 250 cc. of 10 per cent hydrochloric acid. The recovery is about 90 per cent (Note 4), and the purified product melts at 85-86°.
1. Ammonia exerts a hindering effect on this condensation, and the yield is greatly reduced when crude cyanoacetamide is used.
2. At 10°, cyanoacetamide sometimes crystallizes. The mixture should not be filtered until it is certain that the precipitate contains no cyanoacetamide. Any cyanoacetamide which separates redissolves quickly after the acetaldehyde and piperidine have been added.
3. This amide is insoluble in the usual solvents, but it may be further purified, if desired, by trituration with dilute hydrochloric acid, followed by washing with hot absolute alcohol. It then melts sharply at 160-161°.
4. The checkers used one-tenth of the specified amounts of reagents. They obtained, in two runs, the following average yields of products: crude a,a'-dicyano-j3-methylglutaramide, m.p. 152-157°, 75 per cent; crude j3-methylglutaric acid, m.p. 79-82°, 78 per cent; purified j3-methylglutaric acid, m.p. 84-85°, 80 per cent (recovery). In the second run, however, the yields (except for the recovery in the recrystallization) were slightly higher than those given for the larger runs.
3. Methods of Preparation
The above method is adapted from the procedure of Day and Thorpe.1 /3-Ìethylglutaric acid has been prepared by hydrolysis of jS-methylglutaronitrile;2 by condensation of crotonic ester with ethyl sodiocyanoacetate,3 and with sodiomalonic ester;4 and by condensation of acetaldehyde with malonic ester.6
1 Day and Thorpe, J. Chem. Soc. 117, 1465 (1920).