- 173 — 



. Menthadiene. Some years ago we reported that Brunei 1 ) has ob- 

 tained a menthene by heating thymomenthol with bisulphate of potassium 

 or phosphorus pentoxide. In view of the fact that the process of eliminating 

 water by the aid of these reagents tends to bring about intramolecular re- 

 arrangements, G. G. Henderson and R. Boyd 2 ) have synthetised this men- 

 thene by heating thymomenthol with an aqueous solution of oxalic acid, 

 thereby obviating the risk of intramolecular rearrangements. The zl 3 -men- 

 thene prepared by this method had the same properties as Brunei's thymo- 

 menthene: b. p. 167 to 169°, d~ 0,8188, n D 1,45363. It yields a nitroso 

 chloride, m. p. 133°. With bromine a dibromide is formed, from which, 

 when boiled with an excess of alcoholic potash liquor, a menthadiene 

 <m. p. 173,5; df£ 0,8337; n D 1,46539) results. This is probably a ^-men- 

 thadiene. As it was interesting to compare the terpenes with isomeric hydro- 

 carbons CioH i6 , Henderson and Boyd prepared 1,3-diethylq/cZohexadiene from 

 phenol, by converting phenol into 3,5-diethylphenol, and reducing the latter 

 to 1,3-diethylq/cfohexanol. Boiling diethylq/cfohexanol with oxalic acid so- 

 lution gave rise to a mixture consisting for the greater part of 1,3-diethyi- 

 q/dohexene, contaminated with diethyl c^/cfohexadiene. This mixture was 

 converted into diethylq/cfohexene dibromide, from which, when boiled with 

 an excess of alcoholic potash liquor 1,3-diethylq/cZohexadiene (b. p. 166 

 to 168°; df§ 0,8659; n D 1,47575) resulted. The double bond is probably 

 in the 3,5-position. 



Cedrene. A few years ago Semmler and Hoffmann 3 ), while oxidising 

 cedrene with permanganate of potassium in acetone solution, obtained a 

 keto aldehyde or a diketone, together with a cedrene keto acid. In order 

 to gain further insight into the molecular structure of cedrene, Semmler 

 and F. Risse 4 ), have now subjected fairly large quantities of cedrene to 

 oxidation with ozone in glacial acetic acid, as a result of which they 

 obtained oxidation products which in many respects were similar to those 

 prepared with permanganate of potassium. The cedrene employed in the 

 oxidation process boiled between 123 and 124° (12 mm.). The neutral 

 oxidation products formed consisted of a ketone C14H24O or C14H22O 

 (m. p. of the semicarbazone 218°), and a keto aldehyde C15H24O2. If the 

 ketone possessed the formula Ci 4 H 22 0, it would follow that, in addition 

 to the cedrene which was not saturated in the ring (from which only a 

 ketone C14H24O could originate), a semicyclic cedrene was admixed to 

 %e natural cedrene. 



As an acid oxidation product an acid C15H24O3, cedrene keto acid 

 was isolated. The methyl ester of this acid possessed the following con- 



*) Comp. Report April 1905, 103. 



2 ) Journ. chera. Soc. 99 (1911), 2159. 



3 ) Comp. Report April 1908, 28. 

 *) Berl. Berichte 45 (1912), 355. 



