.318 PRACTICAL ORGANIC AND BIO-CHEMISTRY 



borneol or isoborneol and oxidised with permanganate, ozone, or nitric acid. 

 It is a colourless, transparent, tough mass, which crystallises from alcohol and 

 is very volatile, and is used in making celluloid and smokeless gunpowder. 



Sabinane Group. 

 CH 3 CH 3 CH 3 



CH 2 



Sabinene. 



CH 3 



o-Thujene. 



CH 3 CH 3 



CH 3 



/3-Thujene. 



CHo CIL 



CH 3 



Sabinol. Thujone. 



These terpenes are present in various essential oils in small quantities. 



It seems most likely that all the terpenes are made by the condensation 

 of isoprene by the action of acids in the plant juices, and it is most remarkable 

 that so many different isomers can be formed from the unsaturated isoprene. 

 The method of formation of isoprene in plants is unknown, but it may arise 

 by removal of carbon dioxide and ammonia from leucine and isoleucine. 



Caryophyllene, santalene, santalol belong to the sesquiterpene group. 

 They are present in the various essential oils, are yellowish, viscous liquids 

 boiling between 250-280 with slight but not pleasant smell, and they easily 

 change into resins. 



The diterpenes and polyterpenes are also yellow viscous liquids boiling 

 above 300 and not easily volatile with steam. They are found in balsams 

 and resins. 



The resins occur in the plant oils and are also formed from the terpenes 

 by oxidation in the air. Their solutions in the terpenes are generally called 

 balsams ; the solid resins are amorphous shining substances. They con- 

 sist of a mixture of resin acids and dissolve in alkalies from which they are 

 precipitated by acids. They yield various aromatic compounds by fusion 

 with potash and on reduction yield benzene, naphthalene, etc. 



Caoutchouc, the constituent of rubber, is particularly important industrially. 

 The substance which forms caoutchouc can be extracted by ether from the 

 plant juice, and on exposure to light or by action of acids it polymerises to 

 rubber. Pure caoutchouc is soluble in benzene, carbon disulphide, chloro- 

 form, etc. It is acted upon by ozone giving a diozonide. 



It can take up sulphur by kneading with sulphur or by treating with sulpur 

 dissolved in sulphur chloride and this combination constitutes rubber, ebonite. 



The colour of rubber depends on whether lead oxide, antimony oxide, etc., 

 has been used in the vulcanising process. 



