— 190 — 



l°/o aqueous solution of permanganate of potassium, acetone, p-methyl- 

 cyclohexanone, and /?-methyladipic acid result, from which follows that 

 the hydrocarbon possesses the structure of a zl 4, (8) -p-menthene, a body, 

 which has already been obtained by Wallach l ) by condensing bvomo-iso- 

 butyric ester with p-methyl-q/riohexanone. Auwers 2 ) has also recently 

 prepared this hydrocarbon synthetically, starting from pulegone. 



When hydroterpineol is treated with oxalic acid, the result is a 

 hydrocarbon of which the constants agree fairly well with those of 

 J 4(8) -p-menthene: b. p. 170 to 172°, d 20)5 o 0,8175, n D20l5 o 1,45922. 



By treating J 4 ' (8) -p-menthene with sulphuric acid it was inverted into 

 a menthene which yielded menthone when subjected to the action of iodine 

 and mercuric oxide. When oxidised with permanganate of potassium it 

 also gave rise to menthone, in addition to odourless products. 



By this method, therefore, the conversion of pinene *> terpineol 

 -> hydro-terpineol ->- A 4 " (8) -p-menthene ->■ menthene ->■ menthone, may 

 be accomplished. 



J 8 -p-Menthenol-8. When faced with the exceedingly difficult problem 

 of preparing alicyclic hydrocarbons and alcohols in the pure state, chemists 

 have often had recourse to synthesis, although in that case the possibility of 

 rearrangement is not excluded. The most certain results are obtained by 

 preparing the same substance by different processes. Perkin and Wallach 3 ) 

 describe such an instance, in which the question was the synthesis of zl 3 -p- 

 menthenol-8 and of z! 3 ' 8(9) -p-menthadiene. The first-named body had already 

 been prepared some years previously by Perkin jun. and Pickles 4 ) from tetra- 

 hydro-p-toluic acid, and has recently been obtained by Wallach from 

 J 3 -tetrahydro-p-acetyltoluene by Grignard's reaction. Tetrahydro-p-acetyl- 

 toluene was prepared from methyl-q/cfohexene ethane nitrosochloride by 

 the elimination of hydrogen chloride and decomposition of the resulting 

 oxime with acids 5 ). On this occasion Wallach discovered that the nitro- 

 sochloride was not uniform, but was composed of two constituents, one 

 of which occurred in the form of sparingly soluble needles, m. p. 117 to 

 118°, while the second consisted of more readily soluble crystalline tables, 

 m. p. 113 to 114°. The nitrosochloride with the higher m. p. yielded a 

 nitrolpiperidine, m. p. 130 to 131°, that with the lower m. p. another nitrol- 

 piperidine, m. p. 119 to 120°. This is a case of stereo-isomerism, and not 

 of chemical isomerism, as is evident from the fact that the two nitroso- 

 chlorides yield the same oxime (m. p. 116 to 117°). The zl 3 -tetrahydro- 

 p-acetyltoluene which is split off from the oxime by acid boiled at 210 to 





a ) Liebigs Annalen 360 (1908), 72; Report November 1908, 167. 



2 ) Berl. Berichte 42 (1909), 4895; Report April 1910, 162. 



3 ) Liebigs Annalen 374 (1910), 198; Journ. chem. Soc. 97 (1910), 1427. 



4 ) Journ. chem. Soc. 87 (1905), 639; Report October 1905, 90. 



6 ) Liebigs Annalen 360 (1908), 52; 365 (1909), 271; Report October 1909, 205. 



