4 I2 



The phellandrene in Eucalyptus oils has usually a high rotation to the 

 left, so that the diminution, or otherwise, in the normal optical rotations of the 

 crude oils of some species is traceable to the influence of this terpene, 

 consequently the rotation constant is less stable with the phellandrene bearing 

 Eucalyptus oils "than with those in which the predominant terpene is pinene. 

 This difference is more distinctly marked with the oils of those species in which 

 dextro-rotatory pinene and laevo-rotatory phellandrene occur together in some 

 quantity, and the instability of rotations of the phellandrene in these cases 

 is distinctly noticeable. The influence of dextro-phellandrene is also shown in 

 some of the more pronounced phellandrene oils at certain times of the year. 



Unlike pinene, which occurs in both active forms, phellandrene in any 

 Eucalyptus oil has not yet been found in which the dextro-rotatory modification 

 predominates, although the great differences shown in the magnitude of rotations 

 with the oils of the several species in which this terpene occurs, suggests the 

 presence of both active forms. Lsevo-phellandrene is thus the predominant 

 form in Eucalyptus oils, and as practically all those of the phellandrene-bearing 

 Eucalypts have now been investigated, it is hardly likely that the dextro- 

 rotatory modification will now be found to be present in excess in the oils of 

 this genus. 



Phellandrene in Eucalyptus oils is often associated with laevo-rotatory 

 piperitone, but not always, although it may be accepted that the most 

 pronounced phellandrene Eucalyptus oils always contain this ketone in smaller 

 or larger amounts, in ordinary distillates from 5 per cent, in that of E. radiata, to 

 40 per cent, in that of E. dives. 



It is unnecessary to enumerate here those Eucalyptus species in the oils 

 of which phellandrene has been detected, as they are somewhat numerous, but 

 they will be found recorded in the table of general characters and principal 

 constituents. 



Phellandrene was isolated and named by Pesci in 1884 (Gazz. Chim. 16, 

 225), who obtained it from "Water fennel" oil (Phellandrium aquaticum). The 

 terpene he prepared had specific gravity at 10 C. = 0-8558, and specific rotation 

 [a] D + 17-64 (Heusler, Chemistry of the terpenes, p. 109.) Dextro-rotatory 

 phellandrene has, however, been found to occur in the oils of some plants with 

 a much higher rotation than that shown by Pesci. 



Laevo-phellandrene from Eucalyptus oil has previously been shown to have 

 a particularly high rotation, and Schimmel and Co. have recorded the following 

 constants for a sample they prepared: Boiling point 173-175 C. (754 mm.); 

 50-52 (5 mm.) ; specific gravity at 15 C. = 0-848; optical rotation a D 84-10; 

 refractive index at 20 = 1-47694. 



We have prepared a sample of phellandrene from the oil of E. dives, 

 in as pure a condition as possible, which had a considerably higher rotation 

 than that recorded by Schimmel and Co. Our sample gave the following 

 constants: Boiling point 61 (n mm.); specific gravity at 15 C. = 0-845; 

 optical rotation D -- 102-1; refractive index at 20 = 1-4740. The nitrosite, 

 as first prepared, melted at 110-111 C. and had specific rotation, in chloroform 

 solution, [] + 134-8. 



This sample possessed the highest rotation to the left of any of those we 

 have so far prepared. 



In 1903, Semmler [Ber. 36 (1903), 1749] showed that crude phellandrene 

 from Eucalyptus oil contained two isomeric phellandrenes, together with small 

 quantities of cymene and cineol. The phellandrenes on oxidation with potassium 

 permanganate gave distinct acids, and from the study of these oxidation products 

 he considered the acids to have been derived from two different isomeric 



