- 148 — f 



Methylpulegene. H. Rupe 1 ), in collaboration with H. Schobel and 

 E. Abegg, has continued his investigations into terpene homologues, to 

 which we have already repeatedly referred 2 ). The attempts to obtain 

 well-defined compounds by oxidising homomenthene with ozone in glacial 

 acetic acid solution remained without result The authors were more 

 successful with the hydrocarbon methylpulegene, which is formed from 

 pulegone and magnesium methyl halogenide. As oxidation-product they 

 isolated, in addition to acetone, a keto acid, /-methyl-^-acetylvaleric acid 

 (m. p. of the semicarbazone 150°) which, when oxidised with sodium 

 hypobromite, yielded /?-methyladipic acid, and with nitric acid «-methyl 

 glutaric acid. The formation of the keto acid does not permit of any 

 definite conclusions as to the structure of the hydrocarbon. 



In a few cases the authors have succeeded in preparing the tertiary 

 alcohol methylpulegol from pulegone and magnesium ethyl bromide: b. p. 93 

 to 94 (10,5 mm.). In the process of preparing methylpulegene, methyl - 

 menthone (homomenthone) had been formed as a by-product: b. p. 93° 

 (11 mm.), m. p. of the semicarbazone 186°. 



Caryophyllene. In his fifth paper on the sesquiterpenes, E. Deussen 3 ) 

 describes a few derivatives of, as well as a sensitive test for, caryophyllene. 

 When /^-caryophyllene nitrosite is heated with ligroin there results, in 

 addition to dehydrocaryophyllene nitrosate, a body which is distinguished 

 by its insolubility and which can be purified by dissolving it in acetone 

 and precipitating with light petroleum. It crystallises in the pure state 

 in white needles, m. p. 159°, and shows some points of resemblance to 

 Harries' India rubber nitrosite 4 ). (Dec. p. 158 to 162°). The same body 

 is generated when nitrous acid gas is passed into an ethereal solution of 

 caryophyllene. A blue coloration quickly results, and when the passing-in 

 of the gas is continued for some time a voluminous yellowish-white body 

 is precipitated, while the blue colour disappears. Careful re-solution from 

 acetone or hot acetic ester yields a body in the form of well-developed 

 white, silky needles, dec. p. 159 to 160°. In contradistinction to previous 

 statements, this body is optically active: [« D ] — 133°50' (1,037 p. c. solution 

 in acetone). Combustion showed the structure to be C12H19N3O6. Owing 

 to its insolubility in most of the organic solvents, this compound is * 

 excellently adapted for the detection and determination of /^-caryophyllene. ^J 

 For this purpose from 2 to 3 g. of the oil-sample under examination is 

 treated in a 10 p. c. ethereal solution with nitric oxides, the reaction- 

 mixture (which should be protected from light) not being cooled, and the 



!) Berl. Berichte 45 (1912), 1528. 



2 ) Comp. Report October 1906, 130; November 1908, 186; April 1912, 190. 



3 ) Liebigs Annalen 388 (1912), 136. 

 ±) Ibidem 383 (1911), 199. 



