Commercial and scientific notes on essential oils. 69 



terpinene dihydrochloride, m. p. 52°, was suspected to contain sabinene. However, 

 on oxidation with alkaline permanganate solution, no sabinenic acid was obtainable. 



p-Cymene could be proved to be present only after many fruitless attempts, by 

 oxidation of fractions b. p. 175 to 179° with strong permanganate solution, when 

 «-hydroxyisopropylbenzoic acid, m. p. -153 to 154°, was the result. On boiling with 

 strong hydrochloric acid the difficultly-soluble propenylbenzoic acid, m. p. 160 to 161°, 

 was formed. The amount of cymene present is exceedingly small. As far back as 

 1856 Lallemand 1 ) was able to prove the presence of ^-cymene in a thyme oil. However, 

 it must remain an open question whether in this case an oil of different botanical 

 origin was under investigation or whether the j9-cymene had been formed, by a 

 secondary process, from terpinene, an important constituent of the oil. 



y-Terpinene is the main constituent of the phenol-free oil and could be traced in 

 all sub-fractions b. p. 176 to 183°. All of these fractions gave on saturation with 

 hydrogen chloride gas in glacial acetic acid solution, an oily hydrochloride which 

 either was precipitated by addition of water or was obtained on evaporation of the 

 solvent in an open dish after some standing, and could be brought to solidification 

 by strong cooling and additionally after inoculation. When crystallized from methyl 

 alcohol the dihydrochloride melted at 51 to 52°, and in mixture with the corresponding 

 derivative of dipentene very considerable depression of the melting point was observed. 

 From various of the afore-mentioned subfractions there was obtained, on oxidation 

 with alkaline permanganate in the cold, the erythritol C10H20O4 characteristic of /-ter- 

 pinene; m. p. 236 to 237°. On boiling with dilute sulphuric acid in a current of steam 

 a smell of phenols (thymol, carvacrol) was noticed. When several fractions (b. p. 175 

 to 179°; 176 to 178°; 177°) were brominated in absolute ethereal solution, after being 

 chilled down to freezing mixture temperature, separation of a solid, slightly yellow 

 bromide was repeatedly observed which, however, on suction or on spreading on 

 cooled porous plates decomposed rapidly with liquefaction and evolution of hydrogen 

 bromide. Since just these fractions yielded /-terpinene dihydrochloride in good amount 

 it might have been the case of a bromide of /-terpinene. Possibly the investigators 

 working on terpinene have hitherto overlooked the fact that /-terpinene, in absolute 

 ethereal solution at reduced temperature forms a bromide which is unstable at ordinary 

 temperature when exposed to the air. That «-terpinene was absent was concluded 

 from the non-formation of the nitrosite; likewise we were unsuccessful in obtaining, 

 by oxidation with alkaline permanganate, the dihydroxy dimethyladipic acid charac- 

 teristic of «-terpinene which in many cases, besides /-terpinene, is a constituent of 

 essential oils. 



Of alcohols, the following were found to be present: — linalool, borneol, terpinenol-4, 

 and geraniol. 



The first-named alcohol was found in fractions of the b. p. 77 to 78° (6 to 7 mm.) 

 and the sp. gr. di 5 o 0.8975 to 0.8991 which were separated from fractions containing 

 borneol by sharp fractionating. To judge from the odour, an oil of the b. p. 197 to 

 199.5° and the sp. gr. di 5 o 0.8750 consisted of fairly pure linalool from which the 

 phenylurethane, m. p. 65°, was obtained without difficulty on treatment with phenyl- 

 wocyanate. Oxidation with bichromate mixture yielded citral. 



\-Bomeol separated off in the solid state from the fraction b. p. 86 to 102° (8 mm.) 

 when distilling in vacuo, and was identified by its odour, its m. p. 204°, and by the 

 formation of camphor on treatment with bichromate mixture. 



») JahrtsUr. dt. Cham. 9 (1856), 616; ace. to Annal. de Chim. Phys. (3) 49 (1857), 148. 



