d-Camphor, known also as Japanese or Laurus camphor in order to distinguish it from borneo camphor (d-borneol), is obtained on a large scale together with camphor oil by the distillation of the wood of Cinnamomum Camphora with water vapor. d-Camphor has also been found in Siam cardamom oil, American wormseed oil, camphor leaf oil, sassafras oil, apopin oil (?), rosemary oil, spike oil, in the oil of Lavandula Stoechas, Reunion basilicum oil, in the oil of Basilicum canum, and in Dalmatian sage oil; /-camphor in an oil of sage (Salvia grand/flora [?]), Artemisia Herba-alba, A. cana (?), feverfew, tansy, and Blumea balsamifera; i-camphor in the, oil of Chrysanthemum sinense var. japonicum. Camphor has also been reported as being present in a number of other oils, however, without record as to the angle or direction of rotation: in the oils of Piper cam-phoriferum, P. angustifolium var. ossanum, cinnamon root, and of Seychelles cinnamon bark. It may be added that an animal, the Polyzonium rosalbum, probably secretes camphor.1)
1) Cook, Chem. Zentralb. 1901, I. 191.
Synthetically, camphor has been obtained by the dry distillation of the lead1) or calcium-) salts of homocamphoric acid (Haller's hydroxycamphocarboxylic acid). However, this synthesis was only a partial one, since the homocamphoric acid was obtained from a derivative of camphor. The complete synthesis of camphor was later successfully accomplished by Komppa3) who likewise succeeded in effecting the synthesis of camphoric acid.
Camphor can be isolated from the volatile oils containing it by freezing, if necessary after fractionation. It consists of a granular-crystalline, colorless, translucent mass with a decided tendency toward sublimation. It has a characteristic odor and is readily soluble in organic solvents. When cast on water, small pieces rotate in a very lively manner. By various observers its properties have been recorded as follows: d18o 0,9853 (determined for /-camphor);4) m. p. 176,3 to 176,5°; b. p. 209,1° (759 mm., mercury completely within the vapor);5) m. p. 178,4°; [a]D + 41,44° and - 42,76°;6) m. p. 175°; b. p. 204°;7) m. p. 175°; b. p. 204°; [a]D + 44,22° in 20 p. c. alcoholic solution.8)
The world's consumption of camphor is very large, for the manufacture of celluloid ware alone enormous quantities are used. It is also used extensively in the manufacture of smokeless powder, for disinfection and for medicinal purposes. This great demand has given rise to its synthetic production from turpentine spirits on a commercial scale. In general, one of two methods is followed: Either pinene is converted into bornyl chloride by means of hydrogen chloride, which by way of cam-phene and Isoborneol is changed to camphor; or pinene is directly converted into esters of borneol or isoborneol.
1) Haller, Contrib. a l'etude du camphre. These. Nancy 1879, p. 34; Bull. Soc. chim. III. 15 (1896), 324.
2) Bredt and v. Rosenberg, Liebig's Annalen 289 (1896), 5.
3) Berl. Berichte 36 (1903), 4332; 41 (1908), 4470; Liebig's Annalen 368 (1909), 110; 370 (1909), 209.
4) Chautard, Jahresber. d. Chem. 1863, 555.
5) Foerster, Berl. Berichte 23 (1890), 2983.
6) Haller, Compt. rend. 105 (1887), 229.
7) Landolt, Liebig's Annalen 189 (1877), 333.
8) Beckmann, Liebig's Annalen 250 (1889), 353. - As to the influence exerted by the solvent and by the degree of concentration of the solution, compare Landolt, loc. cit, also Rimbach, Zeitschr. f. physik. Chem. 9 (1892), 701.
At all times camphor has aroused the interest of chemists, hence the literature on this subject has grown to large dimensions. In conformity with the object of this book, only those derivatives will be considered that are suited to its identification.
Camphor is a ketone, C10H16O, but does not combine with acid sulphite. With hydroxylamine it yields an oxime (see below) from which, however, the ketone cannot be regenerated in a pure state for the reason that the oxime, when treated with acids, looses water and yields the amide and nitrile, C9H15CN, of campholenic acid.
If in ethylalcoholic solution, or better still in amylalcoholic solution, camphoroxime is reduced with sodium, two isomeric bornylamines result (m. p. 163° and 180° respectively).1) A similar base melting at 159 to 160° results when camphor is heated with ammonium formate to 220 to 230°.2)
Upon reduction with hydrogen camphor is converted into the alcohol borneol, C10H18O. If the addition of hydrogen takes place in indifferent solvents, some isoborneol results, also camphor pinakone, m. p. 157 to 158°.3) In alcoholic solution it is reduced essentially to a mixture of borneol and isoborneol.4)
. Oxidation with nitric acid yields dibasic camphoric acid, C10H16O4 (m. p. of the active compound 187°, of the inactive modification 204 to 205°), and, if oxidized farther, tribasic cam-phoronic acid, C9H1406 (m. p. 139°). From the constitution of the decomposition products of these acids, numerous conclusions as to the constitution of camphor itself have been drawn. Of the many formulas proposed for this ketone, that of Bredt5) given above is alone generally recognized at present.
Dehydrating agents act energetically on camphor. Thus the action of phosphoric acid anhydride yields p-cymene, of sulphuric acid and zinc chloride yields other products as well. The action of iodine results in the formation of carvacrol.
1) Forster, Journ. chem. Soc. 73 (1898), 386.
2) Leuckart and Bach, Berl. Berichte 20 (1887), 104; Wallach and Griepen-kerl, Liebig's Annalen 269 (1892), 347.
3) Beckmann, Berl. Berichte 27 (1894), 2348; Liebig's Annalen 292 (1896), 1.
4) Beckmann, Journ. f. prakt. Chem. II. 55 (1897), 35.
5) Berl. Berichte 26 (1893), 3049.
For the identification of camphor it is converted into the oxime. This compound discovered by Naegeli 1) is best prepared according to the method of Auwers.2) To a solution of 10 p. camphor in 10 to 20 times its weight of 90 p. c. alcohol, a solution of 7 to 10 p. of hydroxylamine hydrochloride and 12 to 17 p. of soda lye are added. The mixture is digested on a boiling water bath until the substance precipitated by water dissolves to a clear solution in soda lye. The oxime precipitated by water is recrystal-lized from alcohol or ligroin. It melts at 118 to 119°.3) The oxime from d-camphor is laevogyrate, that from /-camphor, dextrogyrate.4) [a]D in alcoholic solution +41,3°.
For the identification of camphor the following compounds may also be utilized, viz. the semicarbazone, m. p. 236 to 238°, the p-bromphenylhydrazone, m. p. 101 °,5) the oxymethylene derivative, m. p. 80 to 81 °, and the benzylidene derivative, the active modification of which melts at 95 to 96° and the inactive modification at 78°.
Frequently it is necessary to identify camphor mixed with borneol. According to Haller's method,6) the mixture is heated with succinic or phthalic acid anhydride and rendered alkaline causing the acid ester of borneol to go into solution. From this alkaline solution the camphor can be extracted with ether. According to another method, the borneol can be converted into esters with high boiling point, such as the succinate or stearate, and the camphor distilled over with water vapor. According to a third method, the camphor can be converted into its oxime and dissolved in dilute sulphuric acid. Shaking with ether then removes-ihe borneol. However, the ethereal solution should in turn be snaken repeatedly with dilute sulphuric acid, since the ether also dissolves some of the camphor oxime.
1) Berl. Berichte 16 (1883), 497.
2) Ibidem 22 (1889), 605.
3) Bertram and Walbaum, Journ. f. prakt. Chem. II. 49 (1894), 10; Bredt and v. Rosenberg, Liebig's Annalen 289 (1896), 6.
4) Beckmann, Liebig's Annalen 250 (1889), 354.
5) Tiemann, Berl. Berichte 28 (1895), 2191.
6) Compt. rend. 108 (1889), 1308.