9 — 147 — 



manganate the hydrocarbon which they had recovered from the xanthate. 

 In the course of this manipulation they obtained a yield of 70 to 73 p.c. 

 camphoric acid. From the fraction which had not been attacked by 

 the potassium permanganate they succeeded in isolating a hydrocarbon 

 CioHie, m. p. 64,5 to 65; b. p. 153 to 153,5° ([«] D — 8,34°) which is most 

 probably identical with cyclene. The bornylene which was used for the 

 purpose of oxidation possessed the following properties: m. p. 109 to 110° 

 b. p. 146 to 146,5° (760 mm.), |>] D + 19,30° (in toluene solution). The 

 resolution of the xanthate is best carried out at 176 to 177° by heating 

 the product in a test-tube for about 24 hours in boiling limonene. The 

 bornylene then condenses in the upper part of the tube and may easily 

 be removed with a spatula. No racemisation takes place when the xanthate 

 is decomposed. 



The d-borneol employed in the preparation of Z-bornylene had been 

 placed by us at the author's disposal. 



G. G. Henderson and W. Caw 1 ) do not believe that the' bornylene 

 prepared from the xanthate by Tschugaeff is chemically pure, and suspect it 

 to contain an isomeric terpene. The bornylene, however, which Bredt and 

 Sandkuhl 2 ) prepared from camphor, from primarily-produced camphor- 

 carboxylic acid, borneol-, bornylene-, and bromohydrobornylene carboxylic 

 acid, they regard as absulutely pure. They also regard as chemically 

 pure the hydrocarbon prepared by Bredt and Hilbing 3 ) from /?-iodohydro- 

 bornylene carboxylic acid. 



According to Henderson and Caw, a simple method of obtaining 

 absolutely pure bornylene consists in treating the crude bornylene prepared 

 from its xanthate with hydrogen peroxide in glacial acetic acid. For this 

 purpose they dissolved 50 g. bornylene in 300 cc. glacial acetic acid and 

 heated the mixture with 10 cc. of 30 p. c. aqueous hydrogen peroxide 

 solution to from 60 to 65° until the subliming crystals gave m. p. 110 to 

 112°. After cooling, the bornylene which had separated out was pressed off, 

 and the ethereal solution of the hydrocarbon dried with sodium. The bor- 

 nylene purified by this method has m. p. 113°: [«] D2 oo — 22,27° (8,98 p. c. 

 solution in benzene). As the crude material, ^-borneol, contained a little 

 Z-borneol, the sp. rot. of the bornylene is rather too low. 



The purifying action of the hydrogen peroxide appears to be due to 

 mk the fact that the impurities are more readily attacked than is the bornyl- 

 ene itself. 



On the preparation of nitrosopinene from pinocamphonoxime, see p. 166. 

 On pure «- and /?-thujene, see p. 153. 



*) Journ. chem. Soc. 101 (1912), 1416. 



2 ) IAebigs Annalen 366 (1909), 11; Comp. Report October 1909, 195. 

 *) Journ. f. prakt. Chem. II. 64 (1911), 778; Comp. Report April 1912, 191. 



10* 



