( 7J5 ) 



tieal with eaontchoiic, on account of similar nitrites being formed 

 from them. 



On treatment with sodium and alcoliol, Semmler ') obtained from 

 rayrcene a dihydronijrcene, whicli induced him to suppose the presence 

 in mjrcene of a conjugate system of double links. In connection 

 with the formation of succinic acid from myrcene, and of laevulinic 

 acid from dihydromyrcene, he constructed the following formulae : 



for myrcene: for dihydromyrcene: 



C C— C C C— C 



■\ /' '\ '\ /' '\ 



C = C C = C C=:C C — c 



/^ ' /' /' ' //' 



C C=C C C— c 



8 7 «7 



For a long time, myrcene remained the only known naturally 

 occurring alliphatic terpene. Chapman ') also found it in the oil of hops, 

 Power and Kleber ') rendered its presence probable in the ethereal 

 oil from the leaves of the Sassafras tree, Barbier ^) in the ethereal 

 oil of Lippia citriodora. At Buitenzorg, however, van Rombürgh ') 

 found that the leaves of a variety (sub-vai-iety) of Ocimum Basili- 

 cum L. contained an ethereal oil, in which occurred a still unknown 

 aliphatic terpene which he called ocimene. Apart from its odour it 

 was distinguished from myrcene by a greater index of refraction, a 

 more powerful absorption of oxygen, and by the peculiarity of passing 

 into an isomer at its boiling point at the ordinary pressure. The 

 molecular refraction of ocimene gave a considerably higher value 

 than tiie calculated value for CuHi, so that the proof of the aliphatic 

 character of ocimene was, as yet, wanting. 



The further investigation of ocimene was yielded to me by Prof. 

 van Romburgh; the ocimene formed the subject of my dissertation'). 

 My research, which at first concerned only" ocimene, had soon to 

 be extended to the aliphatic terpenes in general, particularly to 

 rayrcene and the isomer formed from ocimene. 



1) Ber. 34, 3122 (1901). 



2) Journ. of the Ghem. Soc. Trans. 67, 54 (1895) and 83, 505 (1903). 



3) Pharm. Review 1896, Ghem. Gentr. Bl. 1897, II, 42. 

 *) Bull. Soc. Ghim. [3], 25, 691 (1901). 



') Verslagen van 's Lands Plantentuin te Buitenzorg, 1899, p. 48, and These 

 Proc. III. p. 454. 



^) C. J. Enklaar, ,Over ocimeen en myrceen, eene bijdrage tot de kennis van 

 de alipliatische terpenen". Acad, proefschrift, Utrecht, Dec. 1905. A more extended 

 communication will appear in the Rec. des Trav. d. chim. des Pays-Bas. 



50 



Proceedings Royal Acad. Amsterdam. Vol. Vlll. 



