The term cedrene was originally applied to a sesquiterpene obtained by the dehydration of cedrol.2) Upon finding a similar sesquiterpene in oil of cedar, this likewise was designated cedrene. In as much as the identity of these two hydrocarbons has not been proven conclusively, it is best to treat them separately.
The constants of the natural cedrene are recorded as follows:3)
B.p. 124 to 126° (12 mm.); d15o 0,9354; aD - 55°; nD 1,50233.
Natural cedrene has been examined by a number of investigators, more recently particularly by Semmler and Hoffmann.4) Upon oxidation with chromic acid in glacial acetic acid solution, cedrone, C15H240, results, which boils at 148 to 151° (11 mm.) and upon reduction is converted into Isocedrol (b.p. 148 to 151° at 9 mm.). Upon oxidation with permanganate in acetone solution, cedrene yields a glycol, C15H2602, m. p. 160°; a diketone or a ketoaldehyde C15H2402, the semicarbazone of which melts at 234°; and a cedrene keto acid, C16H2403, the semicarbazone of which melts at 245°, the oxime between 180 to 190°.
When oxidized with ozone, cedrene yielded essentially the same products. For its identification, the oxidation with permanganate is resorted to.
1) Berl. Berichte 39 (1906), 752.
2) Walter, Liebig's Annalen 39 (1841), 247.
3) The constants of the artificial cedrene are recorded in the table of the artificially prepared sesquiterpenes on p. 346.
4) Berl. Berichte 40 (1907), 3521.