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CASTOR OIL AS A STARTING MATERIAL FOR LABORATORY PREPARATIONS XORGE ALEJANDRO DOMINGUEZ, ENRIQUE SPERON, and JORGE SLIM Technological Institute for Advanced Studies, Monterrey, Mex'co
CASTOR oil is a readily available natural substance which, by thermal degradation or oxidation, gives four derivatives, I, 11, 111, IV, which in turn can easily be converted into a number of interesting compounds,using procedures which are in general reliable, do not involve unusual risks or complicated methods, and give yields ranging from 40 to 60 per cent. These compounds also can be employed in serial reactions in a manner rarely found in the usual preparations of the organic chemistry laboratory.
The thermal decomposition of castor oil with the isolation and identification of heptaldehyde (enanthol) was lirst carried out by Bussy (1) in 1846. Five years later Bouis (8) added potassium hydroxide, prior to the distillation and obtained sehacic acid. Stanek (3) and Leeds (4) prepared several derivatives of heptaldehyde. In 1877 Krafft (6) identified the second component of the decomposition as undecylenic acid and seven years later found that the amorphous residual. pwte of the distillation is a polymer of undecylenic acid which, by oxidation with nitric acid, gives sebacic acid. A modification of the thermal decomposition of castor oil has been employed by Gmn and Wirth (6) who started with the crude esters of recinoleic acid and obtained the ester of undecylenic acid with a 68 per cent yield. Reaction 1. In a Claisen flask are mixed 150 e. of castor oil and 10 g. of colophony; the usual conneckms for vacuum distillation are set up and the flask is heated with a bare flame. After 6 to 10 minutes the distillate begins to collect in the receiving flask. When approximately 60 to 80 ml. have been collected, the heating is stopped (to avoid the formation of the yellow resinous paste in the flask, which is very difficult to clean). If tn-o layers are formed in the distillate, the
lower layer (water) is taken out in a separatory funnel and the upper layer is poured into a 500-ml. flask to which is attached an efficient rectification column; the distillate passing between 145' and 160°C. is collected (crude heptaldehyde) and, when the temperature rises above 170°, the distillation is interrupted. The crnde heptaldehyde (I) is purified by a second distillation (not necessary if it is going to be used as a starting material for subsequent reactions). The yield is about 24 to 30 g. The residue of the fractional distilation is distilled in a vacuum. The undecylenic acid (11) distils between 156 and 165' a t 30 mm., giving a yield of 25 to 30 g. Reaction 2. Castor oil is heated a t 40' for one hour with a 40 per cent solution of sodium or potassium hydroxide. When cooled, the upper layer is separated, mixed with solid sodium. (or potassium) hydroxide, and heated in a copper or iron basin until the odor of octano2 vanishes (three hours). It is then poured into cool water and the solution is acidified with hydrochloric acid. Sebacic acid (111) is collected by suction (7), the yield being 20 to 40 per cent. Reaction 3. Castor oil is saponified with a methanolic solution of potassium hydroxide, and the recinoleic acid (V) formed is immediately oxidized with an alkaline solution of potassium permanganate. After acidification and purification a yield of 32 to 36 per cent of azelaic acid (IV) is obtained (8). Heptaldehyde (I) undergoes a large variety of reactions, of which the following are characteristic:
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~c!~),cH~
VI Amyl einnamaldehyde
...
Heptanol CH~CHX),CHOI 1-CH,(CH,),COOH (6) VIII Heptanoic acid ACH,(CH,)~CH-CHO
I
Br IX a-Bramoheptaldehyde CH8(CH2)&H=NOH X Heptaldoxime
SEPTEMBER, 1952
447
Reaction 4. Condensation of benzaldehyde with heptaldehyde in a solution of sodium hydroxide. The yield of amyl cinnamaldehyde obtained is 60 to 70 per cent (9). Reaction 5. Reduction of I with iron and acetic acid. Heutanol is formed: yield. 75 to 80 Der cent (10). Reaction 6. Heptaldehyde is oxidized with potassium permanganate in an alkaline medium, and product VIII is isolated by acidification. I t can also he prepared by refluxing I with a solution of sodium dichromate in sulfuric acid. I n both cases the yield is 65 to 75 per cent (11). Reacfion 7. Heptaldehyde is converted with acetic anhydride and potassicm acetate to the heptaldehydn enol acetate (yield, 45 to 50 per cent), nhich is brominated and treated with methanol to give a-bromoheptaldehyde dimethyl acetal (yield, 80 to 85 per cent), which, with diluted hydrochloric acid, is converted to IX; yield, 90 per cent (12). These reactions should only be carried out by advanced students, because they involve the preparation of lachrymous compounds, and require careful control. Reaction 8. Compound I is condensed in an alcoholic medium with hydroxylamine hydrochloride in the presence of sodium carbonate, and heptaldoxime (X) is ohtained; yield, 80 to 90 per cent (13). Compounds VII, VIII, and X are readily converted to a number of interesting compounds, all of which are sufficiently reactive to be used in secondary syntheses. Some of the more interesting reactions are as follows: (9) (10) CHs(CH1),CH10H-CHs(CH1)6CHHB~~ VII XI
of VIII and XIII, and, after refluxing and purification, heptoic anhydride (XIV) is obtained; yield, 70 to 80 per cent (18). Reaction IS. A solution of VIII in an excess of methanol (or ethanol) containing 10 per cent of sulfuric acid is refluxed for three hours, then poured in water. The umer laver is washed several times and purified through-fractibnal distillation, giving a 75 to 85 per cent yield of XV. Reaction 14. An alcoholic solution of X is reduced with sodium. eivine. after ~urification.a 50 to 70 ner cent yield of'hiptyl-;mine (XVI) (19). ' Undecylenic acid (11) may react as follows:
XVII HC=C(CH,),COOH XVIII
Reaction 16. Bromine is added t,o a petroleum ether or carbon tetrachloride solution of 11. The dibromide (XVII) precipitates and can be collected with a yield of 85 to 95 per cent (20, $1). Reaction 16. A suspension of XVII in glycerolpotassium hydroxide solution is heated for two hours a t 100°, then the solution is diluted with water and acidified, when dehydro-undecylenic acid (XVIII) is formed. When purified, the yield is 60 to 75 per cent ($0, $1). Using I11 or IV as starting materials homologous compounds can be obtained. The following illustrates the use of IV, the products obtained from I11 being similar. L O O H (17)
VIII
(12) XI11 (CaH&O)sO XIV
(14) CHdCHXH=NOH-CHa(CH&CHHNH2 X XVI
,COOR (CHA, COOR XIX XXIl
/COOR
Reaction 9. Compound VII can be refluxed with a (CH& 'COOR mixture of red phosphorus and bromine (14) or with XXI anhydrous bromhydric acid (15), or with a sulfuric acid-sodium bromide mixture, giving a 75 to 90 per Reaction 17. Ten per cent of concentrated sulfuric cent yield of heptyl bromide (XI). acid is added t o a solution of IV in methanol (or Reaction 10. Through an intermediate malonic con- ethanol). The mixture is refluxed three hours, poured densation XI is converted to pelargonic acid (XII). in water, and the organic layer is washed, dried, and The over-all yield is 60 to 75 per cent (16). vacuum distilled. The first fraction is the diester, the Reaction 11. Compound VIII is refluxed with second is the monoester. The yield of the diester phosphorus pentachloride. Phosphorus oxychloride (XIX) ranges between 50 and 70 per cent ($2). distils over at 107'" and heptoyl chloride (XIII) at Reaction 18. An alcoholic solution of X I X is al170-180°, according to Lumsden (17). Alternatively, lowed to stand for 24 hours after the addition of the VIII may be refluxed with thionyl chloride, the heptoyl theoretical amount of a 2 N alcoholis potassium chloride formed being purified by fractional distillation; hydroxide solution for the saponification of one of the yield, 70 to 85 per cent. ester groups. Compound X X is ohtained with a yield Reaction 12. Pyridine is added to a benzene solution of 30 to 45 per cent (6, 23). Another and bett,er pro-
JOURNAL OF CHEMICAL EDUCATION cedure is the acidolysis of the diester using anhydrous hydrochloric acid as catalyst (24); yield, 45 to 65 per cent. Reaction 19. By electrolysis of XX in a n alcoholic solution a t 5(t60°, using platinum electrodes and a current of 3 amperes and 30 to 60 volts, hexanodioic acid (XXI) is obt.ained; yield, 30 bo 40 per cent (23,86). Reaction 20. The diester XIX is reduced in alcoholic solution with sodium, and the glycol is extracted with ether and purified by vacuum distillation, to give a 50 to 60 per cent yield of XXII. As an alteinative to the reduction lithium aluminum hydride can be employed (22). The products obtained in all these reactions can be converted to other interesting derivatives. both aliphatic and aromatic. ACKNOWLEDGMENT
The authors wish to express their appreciation for the cooperation and advice of Ing. Carlos Duhne and Ing. Adalberto Reiter, and to the students Berta Gutierrez and Erika Homherg for their help in the experimental work. LITERATURE CITED
(3) (4) (5) (6)
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B o u ~ s J., , ibid., 92, 396 (1854). B o u ~ s J., , ibid., 97, 34 (1856). STANEK, F., J . prakl. Chem., 63, 138 (1854). LEEDS,A. R., Be?., 16, 287 (1883). KRAFFT,F., Be?., 10, 2034 (1877); KRAFPT,F., AND T, BRIJNNER,Be?., 17, 2985 (1884). GRUN.A,. AND T.WIRTH.Ber.. 55. 2207 (1922) TVIIT.'~.N.. Ber.. 7.219'(1874). HII.L,'J. w.,'"o~&~c ~ydtheses,"Col. Val. 11, p. 53. RUTOWSKY, B. N., .4ND A. I. KOROLEW, J. prakl. Chem., 119, 272 (1928).
(14) (15) (16) (17) (18) (19) (20) (21)
CLARKE, H. T., "Organic Syntheses," Col. Val. I, p. 304. R ~ O F FJ., R., "Organic Syntheses," Col. Vol. 11, p. 315; VOGEL,A. I., "A Textbook of Practical Organic Chemistry," Longmns, Green and Co., London, 1948, p. 352. ALLEN,C. F. H., el al., "Organic Syntheses," Vol. 29, p. 14. B o u s s m ~ E. . W.. ibid.. Col. Vol. 11.. . o. 313. VOGEL, A. I., 10c. cil., p. 281. REID,E. E., el al., "Organic Syntheses," Col. Val. 11, p. 246. REID,E. E., ibid.. Col. Vol. 11, p. 474. LUMSDEN, J. S., .I. Ckem. SOC.,87, 90 (1905). BEDOUKIAN, P. Z., "Organic Syntheses." Vol. 26, p. 1. MARVEL, G. S., el d., ibid., COI.Val. 11, p. 318. KRAFFT, F., Be?., 29, 2232 (1896). MYDDLETON, W. W., J . Chem. Soe., 1927, 1928; MYDDLE TON,W. W., AND R. G. BERCHEM, J. Am. Chem. Soc., 49, 2260 (1927).
(22) (23) (24) (25)
CHUIT,P., Heb. Chim. Acta, 9, 264 (1926). CARMICRAE~ M., J. Chem. Soc., 121, 2545 (1922). SWANN, S., el al., "Organic Syntheses," Col. Vol. 11, p. 276. Ruzrcna. L.. AND M. STOLL.Hd". Chim. A&. 16. 493
