- 138 - 



With regard to the synthesis of /?-pinene from nopinone, see 

 under Nopinone, p. 165. 



Camphene. The melting point of natural camphene has frequently 

 been found lower than that of the synthetic body. The question 

 whether this occurrence must be attributed to impurities, or whether 

 it is a case of another hydrocarbon, has induced Wallach 1 ) to make 

 a further examination of the natural camphene of Siberian pine needle 

 oil. It was isolated in this manner, that the fraction of the saponified 

 oil of the b. p. 156 to 165 , was oxidised with alkaline solution of 

 potassium permanganate for . the purpose of destroying the readily 

 attacked portions, and the residue driven off with steam was strongly 

 cooled. The camphene which had crystallised out was filtered off, and 

 purified by distillation and fractional freezing out. It had the following 

 properties: b. p. 160 to 161 ; m. p. 39 ; d 4 oo 0,8555; n D40O 1,46207; 

 molecular refr. found 43,71, calculated for C 10 H 16 / — 43,53; M D — 84,9° 

 in 11,36 per cent, ethereal solution. On oxidising this camphene with 

 potassium permanganate according to Wagner, a dibasic acid C 10 H 16 O 4 

 (m. p. 142 ; Md — 1,166° in 20,85 per cent, alcoholic solution) isomeric 

 with camphene-camphoric acid was formed, of which the chloride, the 

 diamide (m. p. 197 ) and the dianilide (m. p. 21 8°) were produced. 

 It was clear from the melting points of these derivatives, that the acid 

 obtained differs from the hitherto known camphene-camphoric acid. 

 Besides the acid, there were formed in the oxidation, in small quantity, 

 a glycol and an acid yielding a difficultly soluble sodium salt, two bodies 

 the nature of which has not yet been cleared up. The natural 

 camphene yielded isoborneol as readily as the artificial one. When 

 treated with gaseous hydrochloric acid in ethereal solution, a chloride 

 was formed, • which was converted, by splitting off hydrogen chloride 

 with aniline, into a camphene of the m. p. 51 . On brominating, a 

 dibromide of the m. p. 89 was obtained. Wallach assumes that the 

 natural camphene is a physical isomeride of the artificial camphene. 



The camphene worked out from citronella oil yielded on oxidation 

 the same acid melting at 142 as that of Siberian pine needle oil. 



Wallach further produced, for comparison, artificial camphene 

 from bornylamine, obtained by reduction of camphor oxime. The 

 carefully purified base was converted in acetic solution with sodium 

 nitrite, and the reaction-product was distilled with steam and fractionated. 

 The camphene obtained (b. p. 160 to 161 ; m. p. 50 ; [«] D -f- 103,89° 

 in 9,67 per cent, ethereal solution), yielded on oxidation an acid of 

 the m. p. 141 to 1 42°, whose mixture with the acid from natural 



1 ) Nachr. K. Ges. Wiss. Gottingen 1907, Meeting of 20. July. 



