A second well characterized hydrocarbon, which belongs to the bicyclic group of sesquiterpenes, is the caryophyllene. However, it is not as common as cadinene. Up to the present time it has been found in appreciable amounts in the oil of cloves and the oil of clove stems, also in copaiba balsam oil. Furthermore, it has been found in the oils of pepper, betel, Ceylon cinnamon, Seychelles cinnamon (?), cinnamon root, canella alba, pimenta and lavender.
1) Lepeschkin, Journ. russ. phys. chem. Ges. 40 (1908), 698. According to Chem. Zentralbl. 1908, II. 1354.
Up to the present time, caryophyllene has not been prepared in a pure state. The physical constants recorded refer to fractions of clove oil or of oil of clove stems that were not perfectly pure. Caryophyllene obtained by distillation only from oil of cloves mostly contains some aceteugenoll) from which it can be freed by saponification with alcoholic potassa. The sesquiterpene from oil of clove stems does not contain this impurity.
For the caryophyllene from oil of cloves
Wallach2) found: B. p. 258 to 260°; d15o 0,9085; nD 1,50094. Erdmann3) found: B. p. 119 to 120° (9 mm.), 123 to 124° (13 mm.),
258 to 259° (752 mm.); d24o 0,9038. Kremers4) found: d20o 0,9032; [a]D20o - 8,74°"; nD20o 1,50019.
For the caryophyllene from Ceylon cinnamon oil, Walbaum and Huthig5) found: B. p. 260 to 261°; d15o 0,9047; aD - 7°20'.
More recent investigations by Deussen and his colaborers6) would seem to indicate that the fractions of clove stem oil designated caryophyllene consist of at least two isomers, an optically inactive a-caryophyllene, and an active ,B-caryophyllene, both of which have been characterized by derivatives.
According to Schreiner and Kremers7) a dichlorhydrate, crystallizing in needles and melting at 69 to 70°, results from the action of hydrogen chloride upon the caryophyllene-containing fractions of oil of cloves. From the crude caryophyllene of clove stem oil, Schimmel & Co. obtained an active chloride of like melting point. Other investigators obtained from caryophyllene-containing fractions of various oils either liquid chlorides, or chlorides of a different melting point.
1) E. Erdmann, Journ. f. prakt. Chem. II. 56 (1897), 146.
2) Liebig's Annalen 271 (1892), 298.
3) Journ. f. prakt. Chem. II. 56 (1897), 146.
4) Pharmaceutical Archives 1 (1898), 211.
5) Journ. f. prakt. Chem. II. 66 (1902), 54.
6) Liebig's Annalen 356 (1907), 1; 359 (1908), 245; 369 (1909), 41.
7) Pharmaceutical Archives 2 (1899), 296; Proceed. Americ. Pharm. Ass. 47 (1899), 158.
By the action of nitrosyl chloride on caryophyllene from clove stem oil, there results a nitrosochloride melting at about 160°. Upon fractional crystallization, however, it can be resolved into two compounds: an inactive a-caryophyllene nitrosochloride (m. p. 177°) and an active B-caryophyllene nitrosochloride (m. p. 159°). Corresponding with these nitrosochlorides there are an a-nitrol-benzylamine base melting at 126 to 128° and a B-nitrolamine base melting at 172 to 173°. Both of these can also be obtained from the mixture of nitrosochlorides. By splitting off hydrogen chloride the nitrosochlorides yields the corresponding nitroso-caryophyllenes, of which the a-form melts at 116°, the B-form at 120 to 121°.
With nitrous acid anhydride, caryophyllene forms an optically active nitrosite, which crystallizes in blue needles, melts at 115°, and is readily changed to other compounds by the action of solvents. There is also known an active caryophyllene nitrosate, which can be obtained by the action of amylnitrite and nitric acid on caryophyllene or by the oxidation of the blue nitrosite with chromic acid. It melts at 130,5°. Nitrosates of caryophyllene with different melting points are presumably derived from the a-form.
Upon oxidation with permanganate there results, according to Deussen1) and Haarmann2), in addition to a glycol C14H2204 (m. p. 120°), a ketoacid C10H16O3 (semicarbazone melts at 186°), a monobasic acid C8H804 (m. p. 179,5 to 180,5°), and a neutral substance C10H18O3 (m. p. 145 to 146°). The liquid acids which result in this oxidation yield dimethyl succinic acid upon further oxidation.
When acted upon with glacial acetic acid-sulphuric acid mixture, caryophyllene yields a hydrate C15H260, caryophyllene alcohol, melting at 94 to 96°. This alcohol, the phenyl urethane of which melts at 136 to 137°, is optically inactive.
It is noteworthy that upon the dehydration of caryophyllene alcohol caryophyllene is not regenerated, but that an isomeric tricyclic hydrocarbon C15H24, the clovene results. This differs materially in its properties from caryophyllene, but has not yet been found in volatile oils.
1) Liebig's Annalen 359 (1908), 258; 369 (1909), 52; Berl. Berichte 42 (1909), 376, 680.
2) Berl. Berichte 42 (1909), 1062.
When attempting to identify caryophyllene, it should be remembered that the nitrosochloride and the nitrosate are derived from a different hydrocarbon than the blue nitrosite.1) Hence the precaution should be taken to prepare the nitrosite as well as the nitrosochloride or nitrosate.
For the preparation of the nitrosochloride, 5 ccm. of alcoholic hydrogen chloride are added to a well cooled mixture of 5 ccm. caryophyllene, 5 ccm. acetic ether, 5 ccm. alcohol and 5 ccm. ethyl nitrite. Under the influence of sunlight the nitrosochloride soon separates.
For the preparation of the nitrosite, 5 ccm. of glacial acetic acid are cautiously added to a mixture of 5 ccm. caryo-phyllene, 12 ccm. petroleum ether and 5 ccm. of a saturated solution of sodium nitrite. In the cold the nitrosite crystallizes out.
For the preparation of the nitrosate, a solution of 5 ccm. of concentrated nitric acid in 5 ccm. glacial acetic acid are cautiously added to a well cooled mixture of 5 ccm. caryo-phyllene, 5 ccm. glacial acetic acid and 5 ccm. ethyl nitrite. Finally alcohol is added and after 2 hours the nitrosate separates out.
Quite convenient is the preparation of caryophyllene alcohol.2) 25 g. of the hydrocarbon are dissolved in a mixture of 1000 g. glacial acetic acid, 25 g. concentrated sulphuric acid and 40 g. water. After prolonged heating of the mixture, the more readily volatile products are removed by distillation with steam, after which the pure alcohol is obtained by continued distillation.