— 166 — 



Both Kremers and Tilden 1 ) had already observed that the yield 

 of solid nitroso-chloride decreases with the increase in optical activity 

 of the raw material used. We believe that this fact has its foundation 

 in the different degrees of inclination to crystallise of the active and 

 the inactive variety. Several experiments with pinene of different 

 rotation, all carried out in the usual manner under conditions as far 

 as possible similar, clearly showed the dependence of the nitroso- 

 chloride yield upon the degree of rotation of the material employed. 

 While ioo g. of inactive pinene yielded 30 g. nitroso-chloride, 100 g. 

 of pinene with a specific rotation [a] D -|- 46,73° only produced 3,6 g. 

 of inactive pinene nitroso-chloride. But for practical work corresponding 

 allowances must be made as regards the pinene determination, for in 

 certain circumstances the detection of adulterations of essential oil with 

 pinene by the aid of the nitroso-chloride may be impossible if the 

 pinene has a high rotatory power. In such cases oxidation into the 

 active pinonic acid, although less convenient, may give more certain 

 results 2 ). 



It therefore became a matter of great interest to find a pure, 

 optically active pinene, in order that its rotatory power and its be- 

 haviour towards nitrosyl-chloride might be examined. The way to the 

 synthesis of an active pinene had been shown by Tchugaeff's experi- 

 ments 3 ), for that investigator had obtained the racemic compound from 

 i-pinocampheol by his xanthogenate-method. It was therefore to be 

 expected that from the 1-pinocampheol which we had obtained from 

 1-pinocamphone we might derive a pure active pinene. The preparation 

 which was obtained had a pinene-odour and possessed the following 

 constants: b.p.156 (759 mm.), d 15 o 0,8644, « d -|-ii 5'* n Di5° 1,467 93> 

 n D20° ^4662 5, mol. refr. found 43,78, calc. for a hydrocarbon C 10 H 16 /~~ 

 43,54. Although these constants are in agreement with those of 

 pinene, the unexpectedly low rotation caused some surprise. It was 

 found, in fact, that only a small part of the hydrocarbon consisted 

 of active pinene. Not a trace of nitroso-chloride could be obtained 

 from 10 g. When oxidised with permanganate we obtained, besides 

 a little active pinonic acid (m. p. 65°), an acid C 10 H 16 O 4 , probably 

 an isomeride of camphoric acid. It was impossible to determine from 

 which hydrocarbon the latter acid was derived. 



*) Report October 1904, no. 



2 ) In the meantime an article by Wallach has appeared on the same subject 

 (Liebig's Annalen 368 (1906) 6, compare this Report, p. 165). Wallach obtained a 

 similar result in the case of the examination of a synthetically prepared highly 

 active pinene. 



3 ) Journ. Russ. phys.-chem. Ges. 39 (1907), 1324. Through Chem. Zentralbl. 

 1908, I. 1 1 79; Report November 1908, 171. 



