202 TEEPENES CAMPHORS 



Sylvestrene occurs in Swedish and Russian turpentines and in 

 other pine oils. It boils at 176 to 177, has a specific gravity of 0*85, 

 and is dextro-rotatory. It is probably 



CH 



H 2 C C(CH 3 ) 



CH C=CH 2 



Phellandrene occurs in many eucalyptus oils, oil of elemi, and of 

 fennel. Two isomers are said to exist, which have been named a and 

 /?, and two optical isomers of a-phellandrene are known. They all 

 boil at 170 and have a specific gravity of about 0'848, Their constitu- 

 tion is probably 



C CH 3 C=CH 2 



HC CH H,C CH 



I II I II 



H 2 C CH CH 3 H 2 C CH CH 3 



CH-CH. CH-CH 



\ \ 



a-phellandrene. -phellandrene. 



Sesquiterpenes. These are bodies of the empiric composition 

 C 15 H 24 ; many are known but their constitutions have not been thor- 

 oughly made out. They are liquids boiling about 250 to 269, and 

 of specific gravity about 0'90 to 0'936. Cadinene, found in oils of cade, 

 patchouli, etc. ; Caryophyllene, from oil of cloves ; Cedrene, from oil 

 of cedar wood ; Humulene, in oil of hops ; Santalene in oil of santal 

 wood, and Zingiberene in oil of ginger are examples of sesquiterpenes. 



Olefinic Terpenes and Sesquiterpenes. A few compounds, re- 

 sembling the terpenes and sesquiterpenes, have been isolated from 

 essential oils, but differ essentially in having an open chain structure. 

 As an example myrcene, found in oils of bay and sassafras, may be 

 cited. This has a specific gravity of 0'81 and rapidly oxidises by 

 exposure to air. 



It probably has the constitution 



CH 3 CH. 



=CH CH 2 -CH, C CH= 



/ 



CH 3 



2. The Camphors. These may be regarded as the oxidation pro- 

 ducts of the terpenes. They may be divided into alcohols and ketones. 

 As types of the former, borneol and terpineol, both of which have the 

 composition C 10 H 17 OH and menthol, C 10 H 19 OH, may be cited, while 



