This section is from the book "The Volatile Oils Vol1", by E. Gildemeister. Also available from Amazon: The Volatile Oils.
Caparrapene is a sesquiterpene which has been obtained by Tapia5) by the action of dehydrating agents on caparrapiol, a sesquiterpene alcohol occurring in the volatile oil from caparrapi-balsam. The hydrocarbon is a colorless liquid which is readily colored yellow when exposed to light. The following constants are recorded:
1) von Soden and Muller, Pharm. Ztg. 44 (1899), 259.
2) Bull. Soc. chim. II. 37 (1882), 303.
3) Ibidem III. 23 (1900), 543.
4) Arch, der Pharm. 241 (1903), 33.
5) Bull. Soc. chim. III. 19 (1898), 638.
B. p. 240 to 250°; d16o0,9019; [a]D - 2,21°; n 1,4953.
When hydrogen chloride is passed into the glacial acetic acid solution of the sesquiterpene, an active dihydrochloride results melting at 83°.