From the oil of the mammoth fir, Sequoia gigantea, Lunge and Steinkauler 1) obtained a hydrocarbon C13H10 which they named sequoiene. It consists of laminar crystals, with a reddish fluorescence, that melt at 105° and boil between 290 to 300° (uncorr.). It has not been identified with any of the known hydrocarbons of like composition, such as fluorene etc. With picric acid an addition product of red crystalline needles results.

Noteworthy is also the occurrence of naphthalene which has been found in an oil of clove stems, in the oil of a storax bark, and in orris oil. It is readily characterized by its melting point (79 to 80°), its boiling point (218°), and by a picrate that melts at 149°.

Styrene. CH

B Aromatic Hydrocarbons 110

The simplest aromatic hydrocarbon with an unsaturated side chain that is found in volatile oils is styrene (vinyl benzene). It occurs in storax oils and in xanthorrhcea resin oil. It is probably formed by the decomposition of cinnamic acid.

1) Journ. chem. Soc. 69 (1896), 539.

2) Report of Schimmel & Co. April 1896, 66.

3) Arch, der Pharm. 235 (1897), 585.

4) Gildemeister, Arch, der Pharm. 233 (1895), 184.

5) Report of Schimmel & Co. October 1899, 23.

6) Bed. Berichte 13 (1880), 1656; 14 (1881), 2202.

Styrene is a colorless, highly refractory liquid of a pleasant odor, which polymerizes to a transparent, glasslike and odorless mass, metastyrene (C8H8)n, by being kept for some time, and more rapidly by heating, or by contact with acids.

As to its physical properties, the following statements have been recorded:

B. p. 144 to 144,5 V)

B. p. 140° (760 mm); d20o 0,9074; na 1,54030.2)

B. p. 146,2°; d0. 0,9251,3) d 17o/4o 0,90595; nD 1,54344.4)

Pure styrene is optically inactive. Dilute nitric acid or chromic acid mixture oxidize it to benzoic acid. Upon reduction it yields ethyl benzene.

For identifying styrene the well crystallized styrene dibromide C6H5CHBrCH2Br is used, and is obtained by allowing bromine (17 parts) to drop into a solution of the hydrocarbon (10 parts) in twice its volume of ether.5) On evaporation, the bromide separates in crystals, which after being recrystallized from 80 percent alcohol have the melting point 74 - 74,5°.

p - Cymene.

B Aromatic Hydrocarbons 111

Of the hydrocarbons designated as cymenes C10H14, only the meta and para compounds are of importance to the chemistry of the volatile oils. While m-cymene has been observed only as a decomposition or "Abbau" product (Kelbe, dry distillation of colophony; Wallach, dehydration of fenchone; Baeyer, splitting off hydrogen from sylvestrene), p-cymene is a frequent constituent of volatile oils. Up to the present it has been found in Swedish and Russian turpentine oils, in the oil of Cupressus sempervirens, in staranise oil, oil of nutmeg, oil of boldo leaves, oil of Ceylon cinnamon, oil of Seychelle cinnamon bark, cascarilla oil, lemon oil, in the oil of Canarium Cumingii, in the oil of Eucalyptus haemastoma, in oil of ajowan, in coriander oil, in cumin oil, in the oil of Cicuta v/rosa, in angelica root oil, in the oils of Monarda punctata and M. fistu-losa, Sature/a hortensis, S. Thymbra, in the origanum oils from Triest, Smyrna, and Cyprus, in sage oil, in the oils of Thymus vulgaris, Th. Serpyllum, Th. capitatus, and in American wormseed oil.

1) Observations made in the laboratory of Schimmel & Co.

2) Bruhl, Liebig's Annalen 236 (1886), 13.

3) Weger, Liebig's Annalen 221 (1883), 69.

4) Nasini and Bernheimer, Gazz. chim. ital. 15 (1885), 59; Jahresber. d. Chem. 1885, 314.

5) Zincke, Liebig's Annalen 216 (1883), 288.

Like /77-cymene, /7-cymene has frequently been obtained as a transformation product, e. g. from pinene, terpinene, cumin alcohol, laurus camphor, sabinol, thujone, carvenone, dihydro-carvone, carvone, and citral.

The mixture of hydrocarbons known as "thymene", obtained from ajowan oil and used as a soap perfume, consists principally of cymene together with several terpenes (see ajowan oil).

Formerly it was thought that all terpenes were related to this hydrocarbon, that they were its hydroderivatives. According to recent investigations, however, this conception is not wholly correct. It is worthy of mention, that several compounds of the formula C10H16O can be changed top-cymene by the abstraction of water, for instance, camphor and citral.

Cymene is a colorless liquid with an agreeable odor.

B. p. 175 to 176°; d15o 0,8602.0

B. p. 175,2 to 175,9° (752 mm); d 20o/4o 0,8551; nD 1,48456.2)

B. p. 173,5 to 174,5° (763mm); d15o0,8595, d20o0,8588; nD1,479.3)

1) Widmann, Berl. Berichte 24 (1891), 452.

2) Bruhl, Berl. Berichte 25 (1892), 172.

3) Wolpian, Pharm. Zeitschr. f. Russl. 35 (1896), 115.

The following constants were observed in the laboratory of Schimmel & Co. in connection with a preparation obtained from camphor:

B. p. 174,5 to 176° (761 mm); d15o. 0,863; nD15o. 1,49015.

The pure hydrocarbon is optically inactive. Dilute nitric acid also chromic acid mixture oxidize it to p-toluic acid and finally to terephthalic acid. Potassium permanganate attacks it with difficulty. Hence terpenes having a like boiling point can be removed by treating it with dilute permanganate solution in the cold. Should cineol, which boils at the same temperature, be present, it can be removed as its hydrogen bromide addition product. For its identification, cymene is converted into p-hydroxy-Isopropylbenzoic acid (m. p. 155 to 156°) with the aid of concentrated, hot potassium permanganate solution. This acid, when heated with dilute hydrochloric acid, splits off water yielding p-Zsopropenylbenzoic acid (m. p. 160 to 161°); when boiled with concentrated hydrochloric acid it yields an isomeric acid with a boiling point of 255 to 260°.1) For the preparation of hydroxyIsopropylbenzoic acid Wallach2) has given the following directions: 2 g. at a time of the hydrocarbon, prepared as pure as possible, are heated with a solution of 12 g. of potassium permanganate in 330 g. of water on a water-bath with reflux condenser, the mixture being frequently agitated. When the oxidation is complete, the filtrate from the oxides of manganese is evaporated to dryness and the saline residue boiled with alcohol. The potassium salt which is soluble in the alcohol, is decomposed in aqueous solution with dilute sulphuric acid, and the precipitated acid recrystal-lized from alcohol.

The sulphonic acid, produced by treating the hydrocarbon with concentrated sulphuric acid, is also characteristic for cymene. Its barium salt (C10H13SO3)2Ba crystallizes in shining, difficultly soluble laminae and contains three molecules of water of crystallization which can be completely driven off at 100°. The sulphone amide which can be prepared from the chloride of this sulphonic acid melts at 115 to 116°. That cymene sulphonic acid may also result from the action of sulphuric acid on different terpenes must, however, be remembered, also that an isomeric acid is formed at the same time.

1) R. Meyer and Rosicki, Liebig's Annalen 219 (1883), 282. 2) Liebig's Annalen 264 (1891), 10.