Oleum Ligni Cedri. - Cedernholzol. - Essence de Bois de Cedre.
Origin and Production. The red or Virginia cedar, Juniperus virginiana, L. is a shrub or tree that attains a height of 15 m. It is distributed throughout the United States of North America. For a long time its wood has been used in the manufacture of cigar boxes, lead pencils and minor wooden ornaments. The forests of Georgia and Florida, which formerly supplied most of the wood, are almost exhausted. At present Tennessee is the principal center of production and Nashville the principal market for cedar wood. Here also the saw dust and other waste, also the knots, which are said to be particularly rich in oil, are distilled.
1) Hasnsel, Apotheker Ztg. 13 (1898), 510.
2) Observations made in the works of Schimmel & Co.
3) Bericht von Schimmel &j Co. October 1889, 54.
4) Report of Schimmel & Co. April 1906, 17.
The oil which is collected in the drying kilns as a by-product is of inferior quality. These kilns are so arranged that the escaping vapors can be condensed. The higher boiling constituents remain in the wood and only the lower boiling constituents are thus obtained. As a result, the oil is limpid and its odor less delicate and permanent than the normal. Hence it cannot be used in perfumery.
In Germany the waste of the lead pencil factories is used for distillation, a yield of from 2,5 to 4,5 p.c. being obtained. The exhausted chips are used in factories in which skins are prepared for the fur trade.
Properties. Cedarwood oil is wellnigh colorless, somewhat viscid and occasionally studded with crystals of cedar camphor. It has a mild, peculiar but persistent odor. Inhalation of the vapors imparts a violet odor to the urine. d15o 0,943 to 0,961; aD - 25 to - 42°; nD20o about 1,504; A. V. up to about 1; E. V. up to 6,5; E. V. after acetylation 26 to 42. In alcohol the oil is soluble with relative difficulty, for 1 vol. of oil required 10 to 20 vols, of 90 p.c. and up to 6 vols, of 95 p.c. alcohol.
American oils, presumably from the drying kilns of lead pencil manufacturers (see above), had the following properties; d15o 0,940 to 0,944; aD - 40 to - 46°22'; S. V. 2 to 4; E. V. after acetylation 14 to 18; soluble in 5 to 6 vol. of 95 p.c. alcohol.
Composition. The most interesting constituent of the oil, viz. cedrol (see vol. I, p. 401) or cedar camphor was first examined by Walter1) who converted it into cedrene by dehydration with phosphoric acid anhydride. The formula C16 H280 suggested by him was declared improbable by Gerhardt2) who suggested C15H260.
1) Liebig's Annalen 39 (1841), 247.
2) Gerhardt, Lehrbuch der organischen Chemie. Vol. IV, p. 378.
Chapman and Burgess1) studied the liquid portions of the oil. By means of fractional distillation they separated cedrene (b. p. 261 to 262°; d 0,9359; aD- 60°) and compared it with the hydrocarbon of fraction 301 to 306° of sandalwood oil. According to Chapoteaut'-) the hydrocarbons were supposed to be identical. Chapman and Burgess, however, arrived at the conclusion that both hydrocarbons were very similar but not identical.
Rousset3) examined cedarwood oil with the following results: Cedrene, obtained by fractionation - hence natural cedrene - is a sesquiterpene C15H24 (comp. vol. I, p. 340). Under 10 mm. pressure it boils at 131 to 132°; [a]D - 47°54 Upon oxidation of cedrene with chromic acid in acetic acid solution a liquid ketone resulted, to which Rousset assigned the formula C15 H24 0 and which he named cedrone. Reduction converted it into an alcohol C15H26O, isocedrol. Isomeric with this is the cedar camphor or cedrol (m. p. 84°). If cedrol be heated in a sealed tube with acetic acid anhydride, only a part thereof is converted into the ester, the other part is dehydrated to the sesquiterpene. If cedrol be treated with benzoyl chloride no ester whatever results but only the hydrocarbon C15H24. Since cedrol yields neither a ketone nor aldehyde upon oxidation it must be regarded as a tertiary alcohol.
Cedrol is not always contained in cedarwood oil. For years it was sought for in vain in the laboratory of Schimmel & Co. Apparently it is formed when the sawdust or shavings are exposed to the (moist?) atmosphere for a prolonged period.
More recent investigations by F. W. Semmler, together with his students A. Hoffmann4), F. Risse5), K. E. Spornitz6) and E. W. Mayer7) yielded results that differ somewhat from the above.
The natural cedrene was studied first. The results of these investigations are already recorded in vol. I, pp. 340 and 341. The following supplementary statements should be recorded.
1) Proceed, chem. Soc. No. 168 (1896), 140.
2) Bull. Soc. chim. II. 37 (1882), 303; Chem. Zentralbl. 1882, 396.
3) Ibidem III. 17 (1897), 485.
4) Berl. Berichte 40 (1907), 3521. 5) Ibidem 45 (1912), 355.
6) Ibidem 1553. ^ Ibidem 786.
When natural cedrene (b.p. 123 to 124° under 12 mm.) was oxidized with ozone, there resulted as indifferent products a ketone (not determined whether C14H240 or C14H220) and a keto-alde-hyde C15H2402. Of acid oxidation products an acid C15H2403, cedrene keto-acid was isolated, the methyl ester of which possessed the following constants: b.p. 165 to 170° (10mm.); d20o1,0509; aD20o - 32° 24'; nD 1,4882. When oxidized with nitric acid of 27 p.c. strength, this cedrene keto-acid yielded an acid C14H2204 (m. p. 182,5°), the cedrene dicarboxylic acid, the dimethyl ester of which revealed the following constants: b. p. 179 to 183° (13 mm.); dM. 1,0778; a.D - 31°36'; nD 1,48084.
That the cedrene keto-acid C15H2403 is a methyl keto-acid which is closely related to the dicarboxylic acid C14H2204, was demonstrated by the oxidation of the former to the latter by means of alkaline bromine solution.
The question as to the identity of natural and artificial cedrene already alluded to has been solved by the study of their oxidation products by Semmler.
The artificial cedrene was obtained by heating cedrol (m.p. 79 to 80°) with an equal volume of 100 p.c. formic acid for 1/4 hour1). It boiled at 112 to 113° (7 mm.): aD - 85°. Upon oxidation with ozone, in glacial acetic acid solution, this hydrocarbon yielded the cedrene keto-acid which was characterized by its methyl ester (b. p. 166 to 168° under 11 mm.; d19.1,0501; a D - 35°; nD 1,48482).
The cedrene dicarboxylic acid obtained from the artificial cedrene was also identical with the cedrene dicarboxylic acid from natural cedrene. The two products when triturated together revealed no lowering of the melting point.
These experiments demonstrate that the strongly optically active artificial cedrene is contained in the natural cedrene. Inasmuch as the natural product has a higher boiling point, it presumably contains other isomeric sesquiterpenes, probably some semicyclic cedrene.
Semmler 2) likewise succeeded in isolating from cedar wood oil another oxygenated constituent which he named cedrenol.
1) Berl. Berichte 45 (1912), 1554.
2) Ibidem 786.
This is a primary sesquiterpene alcohol. It occurs in fraction 152 to 170° (7 mm.) (aD20o+ 17,5°) of the oil, from which it can be isolated with phthalic acid anhydride in benzene solution. The alcohol, purified through the acetate, has the following properties: b. p. 166 to 169° (9,5 mm.); d20o1,0083; aD20o+ 0°; nD20o 1,5212. The acetate is a colorless liquid, b. p. 165 to 169o (9,5 mm.); d20o 1,0168; aD - 2°; nD20o,1,5021. Cedrenyl chloride boils between 150 and 165° (10 mm.); d20o1,001. Heated with sodium and alcohol, the chloride yields a hydroxyethyl ether and a hydrocarbon which was found to be identical with cedrene, as was shown by its oxydation products cedrene keto-acid and cedrene dicarboxylic acid. Cedrenol is related to cedrene as the two primary alcohols of the santalol series to the santalenes, sesquiterpenes C15H24; and as myrtenol and gingergrass alcohol are related to pinene and limonene. Presumably the primary alcohol group Ch2oh of the cedrenol molecule occupies the same position held by the Ch3 group in both cedrene and cedrol. Their relationship is readily expressed by the following formulas:
In addition to cedrenol, Semmler and Mayer1) have shown the presence of a saturated alcohol in cedarwood oil, viz. pseudo-cedrol. This alcohol is contained in fraction 145 to 155° (10 mm.) from which the cedrenol has been removed by means of phthalic acid anhydride. It boils between 147 and 152° (9 mm.), constitutes a very viscid oil of the composition C15H260, and is characterized by the following constants: d20o0,9964; aD20o+ 21,5°; nD20o 1,5131. It is tertiary in character, for when heated with zinc dust in a sealed tube to 225 to 235°, oxygen was abstracted with the formation of the corresponding saturated hydrocarbon, dihydrocedrene. Moreover, it contained 50 p. c. of cedrene as impurity. In order to purify the dihydrocedrene, ozone was passed into the chloroform solution of the hydrocarbon mixture until added bromine was no longer decolorized. Dihydrocedrene boils between 109 and 112° (10 mm.) d20o 0,907; aD + 37°; nD 1,4882. It differs in its physical properties from the dihydrocedrene which had been obtained by the reduction of cedrene with platinum and hydrogen and which revealed the following constants: b. p. 122 to 123° (10 mm.); d20o0,9204; aD20o + 2C'; aD20o 1 4929. When acted upon by formic acid, pseudocedrol yields cedrene which was characterized by its keto acid and its dicarboxylic acid.
1) Berl. Berichte 45 (1912), 1384.
Cedrol and pseudocedrol are chemically identical and physically isomeric.
Tests and Detection. Adulterations of cedarwood oil have thus far not been observed. Frequently, however, this cheap oil is used for the adulteration of other oils, to which purpose it is admirably suited because of its faint odor. Its presence is recognized by its high specific gravity, its high boiling point, its strong lasvorotation and by its relatively difficult solubility in alcohol. Adulteration with cedarwood oil may be chemically established by oxidation of the cedrene to cedrene keto-acid and cedrene dicarboxylic acid. The suitable fraction (b. p. about 123 to 124° under 12 mm. pressure or 263 to 264° under ordinary pressure) of the oil to be examined is oxidized with potassium permanganate or ozone to cedrene keto-acid C15H2403 (See also vol. 1, p. 340). This is further oxidized by means of alkaline bromine solution or nitric acid to cedrene dicarboxylic acid, m. p. 182,50 1).