An examination in the laboratory of Schimmel & Co.1) revealed that in addition to terpineol, the oil contains a number of other substances previously not observed in the oils of the Abietinead.
The constants of the material used have already been recorded under "Properties." Upon fractionation /-a-terpineol separated as a solid (m. p. 35°; [a]D - 4° 40' in 25 p. c. alcoholic solution, m. p. of the phenyl urethane 111 to 113°).
In the first fraction b. p. 156 to 160° (aD + 10°20') the presence of the following substances was demonstrated; a-pinene (m. p. of nitrosochloride 105 to 107°; m. p. of nitrolbenzylamine 123°), B-pinene (oxidation to nopinic acid) and camphene (the isoborneol obtained by hydration according to Bertram and Walbaum melted at 208 to 209°).
The fraction, b. p. 170 to 180° (aD - 12°55') consisted principally of /-limonene and dipentene (m. p. of dipentene dihydro-chloride 48°; m. p. of tetrabromide 122 to 123°). The tetra-bromide obtained from fraction 175 to 177° was a mixture of limonene and dipentene tetrabromides. These were separated by fractional crystallization. The fraction that melted at 103 to 106° consisted of optically active tetrabromide (limonene tetrabromide), the more difficultly soluble fraction melted at 120 to 123° and was dipentene tetrabromide.
Fraction 174 to 180° also contained cineol which was converted into cineol resorcinol by shaking it with resorcinol solution. The cineol separated from this solution was identified by means of the iodol compound which melted at 110 to 112°.
Fraction 178 to 180° contained a small amount of /-terpinene. The erythritol obtained by oxidation with permanganate melted at 232 to 235°.
1) Report of Schimmel & Co. April 1910, 103.
In the attempts to learn more about other constituents, the presence of a-terpineol interfered. Hence it was converted into terpin hydrate by shaking with dilute sulphuric acid. By means of steam distillation the other substances could be separated. The oil thus obtained was repeatedly fractionated. In this manner it was possible to isolate borneol, also methylchavicol, a substance previously not found in a Pinus oil.
The oil remaining after the hydrocarbon had been distilled off contained larger amounts of borneol (m. p. of borneol phthalic acid 164°). Fraction 210 to 215° was boiled with 100 p. c. formic acid for an hour for the purpose of removing terpineol. The bornyl formate, purified by fractionation, was saponified with potassium hydroxide. The solid borneol thus obtained, when recrystallized from petroleum ether, melted at 204° and was lasvogyrate (m. p. of phenyl urethane, 137 to 139°; the semicar-bazone of the camphor, obtained upon oxidation with chromic acid, melted at 237°).
The fractions in which the borneol was found also contained methylchavicol. After the borneol had been removed by means of its acid phthalic ester, the crude methylchavicol (d15o 0,9710; aD - 0°27'; nD20o.1,51726) boiled at 73 to 74° (4 to 5 mm.) and at 215° (758 mm.). Upon oxidation with permanganate, homoanisic acid (m. p. 83 to 84°) and anisic acid (m. p. 183 to 184°) resulted. When boiled with alcoholic potassa, anethol (b. p. 230 to 233°, m. p. above 15°) resulted.
The fractions following possessed a musty odor. They consisted largely of /-fenchyl alcohol. Fenchone could not be detected. However, from the fractions, from which fenchyl alcohol had been removed, a small amount of a semicarbazone, m. p. 233 to 235°, was obtained which was identical with camphor semicarbazone. Camphor, therefore, is present in traces only.
The identity of the /-fenchyl alcohol (b. p. 201 to 204°; m. p. 33 to 35°, when quickly heated 37 to 38°) was established by means of the acid phthalic ester (m. p. 142 to 143°). The ketone obtained by the oxidation of the alcohol with chromic acid (b. p. 192 to 193° and 193 to 194° respectively: d15o0,9501; nD20o1,47021), was isofenchone (m. p. of oxime when quickly heated 159 to 160°).
This investigation therefore reveals that in addition to /-a-terpineol, "yellow pine oil" contains a- and B-pinene, camphene, /-limonene, dipentene, y-terpinene, cineol, i-fenchyl alcohol, camphor, /-borneol, and methylchavicol. Thus the presence of cineol, fenchyl alcohol, camphor and methylchavicol in an oil of the Abietineee has been demonstrated for the first time.
Origin and Production. Since the middle ages, pine tar oil and wood vinegar are obtained as by-products in the production of tar and charcoal by means of destructive distillation of the wood rich in resin and of the roots of Pinus silvestris, L. In Russia, Pinus Ledebourii, Endl. (Larix sibirica, Ledebour) is said also to be used1). The industry is restricted to districts with large pine forests. In continental Europe most of the pine tar oil is produced in Eastern Germany, in Poland, in Finland and other parts of Northern Russia, also in Sweden.
The crude pine tar oil contains empyreumatic substances. Formerly it was purified merely by rectification with milk of lime or according to similar methods. Since more is known about these impurities, the oil is treated with dilute caustic soda solution which condenses diacetyl and its homologues to quinones of the benzene series, and which also destroys the unpleasant smelling substances of the lowest fractions. Subsequent treatment with moderately concentrated sulphuric acid resinifies furfurane, aldehydes and unsaturated compounds. Stronger sulphuric acid should be avoided, since it attacks the terpenes as well. These methods of purification, however, are not always sufficient, hence a number of patented2) processes are likewise employed.
But even the most carefully treated pine tar oil will never be identical with turpentine oil as to its properties since its chemical composition differs from that of the latter oil. For some uses this is of no consequence, for many purposes, e.g. for medicinal, turpentine oil can not be re-placed by pine tar oil.
1) Tilden, Pharmaceutical Journ. HI. 8 (1878), 539.
2) See footnote 2, p. 47.
Aside from its odor pine tar oil differs from turpentine oil by its very slight oxidation capacity, i. e. in its inability to absorb larger amounts of oxygen.
Properties. According to the character of the oil, as to whether it is crude, superficially purified, or completely freed from admixtures, pine tar oil differs materially as to its physical constants. Crude and poorly rectified oils possess a decided empyreumatic odor due to phenols that can be removed by shaking out the oil with soda lye. However, even carefully purified oil has an odor distinct from that of turpentine oil.
The sp. gr. of purified oil varies from 0,860 to 0,875, that of crude oil is lower; aD +4 to +16°; nD20o 1,469 to 1,480; when distilled, only a small fraction, as a rule, distils over between 155 and 162°, whereas the bulk distils between 162 and 170° and higher.
Hence pine tar oil differs from turpentine oil in regard to its boiling temperature. This is due to the lower pinene content and to the predominance of higher-boiling terpenes, such as sylvestrene1) and dipentene. The detection of pine tar oil can, therefore, be accomplished chemically by means of the isolation and identification of dipentene and sylvestrene, terpenes characteristic of pine tar oils'2). In most instances, however, the color reactions of Herzfeld, Valenta and Utz described on p. 48 will suffice.
Composition. The several varieties of pine tar oils have, in general, the same composition. The constituents are: d-a-pinene, B-pinene, d-sylvestrene, limonene, cymene, and sesquiterpenes. In addition to these hydrocarbons, the crude oil contains oxygenated constituents, that are due to the heat employed in the destructive distillation, and are to be regarded purified, light greenish oil is obtained, which, when rectified a second time over lime, yields a colorless oil (Essence de tere-benthine blanche rectifiee).
1) In order to ascertain whether sylvestrene and dipentene occur as original constituents in the wood of the pine or whether they are changed products produced during the process of distillation, Aschan and Hjelt (Chem. Ztg. 18 , 1566) distilled the wood of the trunk with steam. Pinene and sylvestrene were found in the oil, but no dipentene. Hence sylvestrene appears to be a normal constituent of the pine, whereas the dipentene found in the pine tar oils appears to be an inversion product produced from the pinene under the influence of heat.
2) Sylvestrene also occurs in Russian as well as in Indian turpentine oil.
Properties. German pine tar oil has a terebinthinate, empyreumatic odor, a light yellow color; sp. gr. 0,865 to 0,870; aD + 9 to +22°. A normal pine tar oil upon fractionation yielded 21,6 p. c. between 160 and 165°, 50,4 p. c. between 165 and 170°, 15,2 p. c. between 170 and 175°, 6,4 p. c. between 175 and 180°, residue 6,4 p. c.
Constituents. German pine tar oil contains d-pinene, d-sy/-vestrene and dipentene and does not differ in composition from the Russian, Polish and Swedish oils.