A, 3-phellandrene

Two isomeric terpenes are known under the name of phellandrene. Before the distinction between the two bodies was recognised, phellandrene had been discovered and reported in a number of essential oils, so that in many cases it is impossible at present to decide which isomer is that actually present in a ven oil. The two terpenes—still another case of the absurd nomenclature which has been retained for so many of the terpenes—are known as a-phellandrene and /3-phellandrene. The constitutions of the two hydrocarbons are probably as follows —... 

He found that the d-phellandrene from elemi and bitter fennel oils were identical, and that i-phellandrene from eucalyptus oil is the laevo-rotatory variety of the same terpene. To these he assigned the names d-a-phellandrene and i-a-phellandrene. The d-phellandrene from water fennel oil differs from these and is named d-/3-phellandrene. The following are the characters of the purest specimens of natural phellandrene yet obtained —... 

If a-phellandrene be oxidised by potassium permanganate, the principal body resulting is a-oxy-/3-isopropyl glutaric acid. If /3-phellandrene be oxidised, closely related acids result, but if a 1 per cent, solution of permanganate be used and the oxidation effected very carefully in the cold, with the terpene always in excess, a glycol, CjoHjg(OH)2, results, which when dehydrated with dilute sulphuric acid yields tetrahydro-cuminic aldehyde. 

If the a-phellandrene nitrite be heated with an alcoholic solution of potash, it is converted into nitrophellandrene, Ck,Hi5(N02). This bodyis converted by reduction with sodium and alcohol into tetrahydrocarvone, or by less energetic reduction with zinc and acetic acid, into carvotan-acetone. The relationship between these bodies is shown by the following formulas —... 

Wallach has prepared a-phellandrene synthetically from sabinenic acid by oxidising it to sabina ketone with potassium permanganate. This ketone was converted into its semicarbazone, and the latter compound treated with dilute sulphuric acid, when sabina ketone is not regenerated, but an isomer, which was found to be isopropyl-hexenone. By the interaction of this body with methyl-magnesium iodide, loss of water occurs with a simultaneous conversion into a-phellandrene, which appears to be a mixture of the dextro- and laevo- varieties. This syntheticallj prepared a-phellandrene has the following characters —... 

For olibanum, six characteristic diterpenes were observed cembrene A (94), cembrene C (98), isoincensole acetate (104), a dimer of a-phellandrene (86) and two unidentified compounds (92) and (103). 

B. frereana and B. papyrifera olibanum have very different terpenic composition from the others. B. frereana olibanum contains the same monoterpenes as olibanum from B. carteri, B. sacra or B. serrata, but is very poor in sesquiterpenes and contains none of the diterpenic biomarkers cited before. Two unidentified compounds (55 and 56) seem to be specific and the main diterpenes, present in high level, are four dimers of a-phellandrene. Dimer 3 (113) is the major component. On account of its absence in the other olibanum samples, it can be considered as characteristic of B. frereana olibanum. 

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