TERPENES  PROPER The terpenes proper may be subdivided into the

simple mono-cyclic terpenes and the more complex (usually bicyclic) terpenes . The monocyclic terpenes are hydro derivatives of paracymene . A. v . Baeyer proposed the following nomenclature: the dihydroparacymenes are called terpadienes, the tetrahydrocymenes be-coming terpenes and the hexahydrocymene terpan, the carbon atoms being numbered as shown in the inset formula: In the more complex terpenes the name camphene is retained, and camphane is 42 3\ (8)l C (9) used for the dihydrocamphene . G . (~) C \o 5~—C \C (to) Wagner (Ber., 1894, 27, p . 1636 Anm.) designates the hexahydrocymenes menthans, the tetrahydrocymenes menthenes, and the dihydrocymenes menthadienes .