( 700 ) 



Chemistry. — ''On ocimene". By Prof. P. van Rombukgh. (Com- 

 municated by Prof. C. A. Lobry dk Bruyn). 



(Communicated in the meeting of February 27, 1904). 



At the December meeting 1900, I Iiad the lionour to submit to 

 the Academy a communication on the essential oil from an Ocimum 

 Basilicum L. which contains besides a large quantity of eugenol, a 

 hydrocarbon of the formula C^^^,, to which I gave the name of 

 Ocimene. The peculiar behaviour of that hydrocarbon reminded me 

 of the olefmic terpenes, discovered by Semmler, of which myrcene, 

 isolated by Power and Kleber, was the best known. Ocimene, 

 however, did not appear to be identical with myrcene. 



Chapman^) has shown some time ago that the essential oil of hops 

 contains 40 — 50 "/„ of an olefmic terpene which he considers to be 

 identical with myrcene. In his papei-, Chapman disagrees witii my 

 observation that myrcene is not so changeable as stated by Power 

 and Kleber. According to these investigators this substance becomes 

 polymerised after standing foi' a week, whereas I could preserx^e it 

 for months, of course in a properly sealed bottle. Chapman refers to 

 a paper of Harries '') to show the unstability of myrcene. Tiiere we 

 read however, only that the polymerisation "sehr leicht zu bewirken 

 ist durch langeres Stehen oder durcli mehrstiindiges Erhitzen auf 

 300"^", wdiilst Semmler'), in accordance with my observations, says 

 that he found it to be "überhaupt nicht so leicht veranderlich". 

 ' The olefuie terpene from hops has the power of absorbing oxygen, 

 like ocimene. In one of Chapman's experiments 16 cc. of oxygen 

 were absorbed in three days by 1 cc. of the terpene. I had already 

 found previously that myrcene does not absorb in the same time any 

 notable quantity (only fractions of a cc.) and, recently, on repeating 

 my experiments I found my previous observation confirmed. If, 

 however, myrcene was left in contact with oxygen for a long time 

 (in tubes 1.5 cm. in diameter) the volume of the gas began to de- 

 crease gradually, but with increasing velocity, so that after 16 days 

 30 cc. had been absorbed. Of a sample of ocimene which had been 

 kept in a properly sealed bottle for three years and had twice made 

 the journey to and from Java, 1 cc. absorbed 17.8 cc. of oxygen in 

 11 hours; in the case of this terpene I again noticed that after 



1) Journ. of the Ghem. Soc. Trans 1903. 83 p. 505. 



2) Berl. Ber. 35 (1902). S. 3259. 



3) Berl. Ber. 34 (1901). S. 3126. 



