Phellandrene belongs to those hydrocarbons C10H16 that are widely distributed. In nature it occurs in several modifications. According to Wallach1), phellandrene is defined as "a hydrocarbon C10H16, which when brought into contact with N203 in an in-different, non aqueous solvent (ligroin) at a temperature below 0° - hence under conditions that exclude inversion as much as possible - yields at once a well characterized nitrite".
Of the natural phellandrenes the a- and the B-varieties should be kept quite distinct. Of the a-variety, the d-a-phellandrene has been found in gingergrass oil, schinus oil, bitter fennel oil, the Spanish dill herb oil, both Ceylon and Seyphelle cinnamon oil, and elemi oil; the l-a-phellandrene in Australian eucalyptus oil and star anise oil.
In most other instances when the presence of phellandrene has been reported, it does not become apparent which phellandrene it is that has been identified. In most instances, however, it appears to be a-phellandrene which appears to be accompanied by traces of B-phellandrene. Hence the conditions appear to be similar to those observed in connection with a- and B-pinene. In addition to the occurences mentioned above, phellandrene has been found in the following volatile oils:
1) Liebig's Annalen 336 (1904), 10.
Without reference to the optical rotation, the presence of phellandrene has been recorded in the oils of Juniperusphoenicea, Andropogon laniger, curcuma, ginger, pepper, magnolia, Mono-dora Myristica, Cinnamomum pedunculatum (bark), cinnamon root, camphor, sassafras leaves, geranium, frankincense, Eucalyptus acmenoides, angophoroides, capitellata, coriacea, crebra, Dawsoni, Delegatiensis, dives, fastigiata, Fletcheri, fraxinoides, haemastoma, loxophleba, Luehmanniana, macrorrhyncha, me-lanophloia, meliodora, microtheca, nigra, obliqua, oreades, ovali-folia, o. var. lanceolata, pulverulenta, radiata, Risdoni, robusta, rostrata, siderophloia, sideroxylon var. pal lens, Sieberiana, stellulata, viminalis, virgata, vitrea, in German and English dill oil. in the oil of ajowan herb, and in the oils of peppermint, wormwood, goldenrod, and dog fennel.
The phellandrenes belong to the least stable of the terpenes. Hence, when it is desired to isolate phellandrene from a volatile oil or to identify it, the oil should not be distilled repeatedly under ordinary pressure, but should be fractionated under diminished pressure.
Synthetically, a-phellandrene was obtained by Harries and Johnson,1) also by Wallach.2) However, the products obtained were not of unquestioned purity. The only crystalline derivatives of the phellandrenes, the nitrosites, do not lend themselves to the regeneration of the hydrocarbon. They are decomposed with alkali,3) but no hydrocarbon C10H16 results. In the study of phellandrene, it is therefore necessary to be content with fractions rich in phellandrene. For this purpose the fraction 170 to 178° is usually taken. The properties of phellandrene, as recorded, pertain to such fractions.
1) Berl. Berichte 38 (1905), 1832. 2) Liebig's Annalen 359 (1908), 283.
3) Wallach, Liebig's Annalen 287 (1895), 374; 336 (1904), 30.
Of the constants observed, the following may here be mentioned: l-a-Phellandrene from the oil of Eucalyptus amygdalina.1)
B. p. 173 to 175° (754 mm.), 50 to 52° (5 mm.); d16o 0,848; aD - 84° 10'; nD20o 1,47694.
d-a-Phellandrene from gingergrass oil: 2) b. p. 44 to 45° (4 mm.), 175 to 176° (754 mm.); d15o, 0,8565; aD-f-40°40'.
d-a-Phellandrene from elemi oil:3) b. p. 61° (11 mm.); d19o 0,844; nD19o 1,4732.
B-Phellandrene from water-fennel oil: b. p. 57° (11 mm.); d20o 0,8520; nD20o 1,47884) and d18o 0,848; [a]D + 14°45'; nD18o 1,4759.5)
The optical rotation is very variable. It is reduced by the action of sun light.6)
As already pointed out, phellandrene is relatively unstable. When heated to its boiling point it is polymerized. By the action of acids it is even more readily changed to inactive isomers. Thus by the action of hydrohalogen it is converted into dipentene, by alcoholic sulphuric acid into terpinene. When acted upon by halogen or hydrohalogen, liquid compounds mostly result. When oxidized with potassium permanganate, a-phellandrene yields the oily a-hydroxy-B-isopropylglutaric acid, which, upon further oxidation with lead peroxide and sulphuric acid, is converted into isopropylsuccinic acid. The oxidation products obtained from B-phellandrene are a-hydroxy-B-isopropyladipic acid and a-isopropylglutaric acid respectively.7) Upon oxidation of B-phellan-drene with a one percent, solution of potassium permanganate, Wallach8) obtained, in addition to /l2Isopropylcyclohexanone, a-isopropylglutaric acid, isobutyric acid, and an oily glycol. When acted upon with dilute sulphuric acid, this glycol yielded tetrahydrocuminic aldehyde and some dihydrocuminic alcohol. When B-phellandrene is oxidized with oxygen from the air, v2Isopropyl-cyclohexanone results.1)
1) Observations made in the laboratory of Schimmel & Co. 2) Report of Schimmel &Co. April 1904, 56. 3) Wallach, Liebig's Annalen 336 (1904), 12.
4) Ibidem 43.
5) Ibidem 340 (1905), 2.
6) Bacon, Philippine Journ. of Sc. 4 (1909), A. 101.
7) Semmler, Berl. Berichte 36 (1903), 1749.
8) Liebig's Annalen 340 (1905), 12.
The only solid derivative of phellandrene is its nitrite resulting upon the addition of nitrous acid, hence this is used for its identification. Both phellandrenes yield two nitrites, which, as first pointed out by Schreiner,2) are distinguished by their melting points. In order to ascertain whether an oil contains phellan-drene, a solution of 5 g. of sodium nitrite in 8 g. water is placed beneath a layer of a solution of 5 cc. of the oil in 10 cc. of petroleum ether. 5 cc. of glacial acetic acid are then added while shaking the mixture for the purpose of generating the necessary nitrous acid. The voluminous crystalline magma is removed with the aid of a force filter, washed first with water and then with methyl alcohol, and finally purified by repeated solution in chloroform and subsequent precipitation with methyl alcohol.3) The crude phellandrene consists of two modifications and the more soluble nitrite is lost in the above process. If it is desired to ascertain which phellandrene is present in a given oil, it is necessary, therefore, to purify with the aid of acetone.1) When precipitated fractionally with water, the nitrite of a-phellandrene can be separated into its two modifications melting respectively at 112 to 113° (or 113 to 114°) and 105°; B-phellandrene into its two modifications melting at 102° and 97 to 98° respectively. All of these have different angles of rotation, partly dextrogyrate, partly lasvogyrate.
Unlike terpinene nitrosites, the phellandrene nitrites cannot be converted into nitrolamines. When treated with sodium alco-holate, a-phellandrene nitrite yields nitro-a-phellandrene. Upon reduction with zinc and glacial acetic acid, this yields carvotan-acetone and dihydrocarvylamine. The more energetic reduction with sodium in alcoholic solution yields tetrahydrocarvone and tetrahydrocarvylamine.5) B-Phellandrene, when treated with sodium alcoholate, yields nitro-B-phellandrene. When reduced, this is converted into dihydrocuminic aldehyde (m. p. of the semicarbazone 200 to 202°), tetrahydrocuminylamine and cuminylamine.
1) Liebig's Annalen 343 (1905), 29.
2) Pharmaceutical Archives 4 (1901), 90.
3) Wallach and Gildemeister, Liebig's Annalen 246 (1888), 282.
4) Wallach, Liebig's Annalen 336 (1904), 13. 5) Ibidem 30, 44.
For the oxidation of B-phellandrene the oxidation with a one percent, solution with potassium permanganate may also be re-sorted to, yielding a syrupy glycol (b. p. 150° at 10 mm.).1) When heated with dilute sulphuric acid, this glycol is converted into dihydrocuminic alcohol and tetrahydrocuminic aldehyde (b. p. 220 to 230°; d20o0,93; nD20o 1,4903; m. p. of the semicarbazone 204 to 205°. As byproducts isopropyl-1-cyc/ohexene-2-one-4, and a-Isopropylglutaric acid, and isobutyric acid result.