Notes on scientific research. 



double bonds was proved by the formation of the terpene from verbenol (I), by the 

 value found for the molecular refraction (44.57, calc. for j\ 43.05), and by the behaviour 

 of verbenene towards bromine. The easily-obtainable dibromide was strongly optically 

 active, the rotation being opposite to that of the primary material, and gave rise, on 

 treatment with dilute potash solution, to an unsaturated glycol Ci H 16 O 2 (IV; m. p. 141°) 

 and to an apparently oxide-like body which was not examined further. The authors 

 were unsuccessful in trying to replace the bromine atoms by hydrogen. On the other 

 hand, dihydroverbenene (V; b. p. 158 to 159° [726 mm.]) was formed on treating the 

 terpene with sodium and alcohol. (Cf. Semmler, On the reduction of a-phellandrene, 

 Berl. Berichte 36 [1903], 1035 and 1753.) Dihydroverbenene, which may be taken for 

 a <?-pinene, strongly resembled a-pinene in its physical and chemical properties, such 

 as the formation of pinene hydrochloride on introducing dry hydrogen chloride, or of 

 a nitroso body identical with nitrosopinene from the nitrosochloride. Hence the authors 

 believe that «-pinene is primarily formed by the action of acid reagents. 

 CH C COOHCH 



OHHC 



C-CH 3 



(I) Verbenol. 



C-OH 



CH, 



CCH 3 



(II) Verbenene. 



(CH 3 ) 2 C 



HOOC 



(III) Norpinic acid. 



H 2 C 



C(OH)CH s 



(IV) Glycol from verbenene 

 dibromide. 



HC 



CH-CH 3 



(V) Dihydroverbenene, 

 J-pinene. 



C-CH 3 



(VI) a-Pinene. 



Pinene. — By repeated fractional distillation, in vacuo, of 15 litres of French turpentine 

 oil, Pariselle 1 ) obtained: — a-pinene, b. p. 153.5 to 154.5° (760 mm.), or 62° (32 mm.), 

 d o 0.8748, [«] D i50 — 43,48°, n D130 1.4690, rot. disp. 1 (A = 589), 1.185 (A = 546), 1 .44 (/L = 492), 

 2 (/- = 436), coefficient of viscosity 0.0141, mol. refr. 43.85, and ^-pinene, b. p. 163 to 164° 

 (760 mm.), or 71.5° (34 mm,), d o 0.8848, d 15 o 0.8728, [a] D15Q — 19.80° rot. disp. 1 (A = 589), 

 1.1 (2 == 546), 1.15 (I = 492), 1.08 (?) {I = 436). 



With hydrogen bromide, a-pinene yielded the solid pinene hydrobromide, m. p. 94°, 

 b. p. 94° (12 mm.), [a] D150 +27.95° (in toluene solution), and a liquid hydrobromide 

 which contained the solid isomeride in the dissolved state. ^-Pinene showed exactly 

 the same behaviour and gave a solid monohydrobromide with nearly the identical 

 physical constants, except [a] D150 being —31.50°. By the action of bromine on a-pinene 

 Pariselle obtained the solid monohydrobromide, a liquid monohydrobromide, a dibromide 

 (m.p. 150° with slight decomposition at 130°), and Wallach's dibromide (m.p. 166 to 168°) 3 ). 



By synthesising pinocamphone and a-pjnene from monocyclic bodies, L. Ruzicka 

 and H. Trebler 3 ) were able to prove the correctness of Wagner's pinene formula (1), 



; ) Compt. rend. 172 (1921), 1496. — 2 ) Cf. LieUg'8 Annalen 264 (1891), 7. — 3 ) Helv. chim. acta 4 (1921), 666. 



