P - 161 — 



also dihydropinolone (as oxime) and dihydropinylamine resulted. It may 

 therefore be considered as proved that isocamphor already contains a 

 pentacyclic ring, and that it is not, as supposed by Angeli and Rimini, a 

 A 6 -methyl- 1 nsopropyl-5-C2/cZohexenone-2. 



Menthenone. zl 4 -menthenone-3 (I) has b. p. 212°, its isomeride, 

 /^-menthenone-a (II), has b. p. 235 to 237°. This difference of from 22 to 

 24° is the more remarkable because the two compounds carvenone (III) 

 (b. p. 232 to 233°) and carvotanacetone (IV) (b. p. 228 to 229°) of which 

 the structure is to some extent analogous, only show the slight difference 

 of 4° in their boiling-points. It would therefore appear to be not beyond 

 doubt that there is some error in regard to the characters or the con- 

 stitution assigned to zJ 4 -menthenone. Auwers 1 ) also expressed himself 

 to this effect some time ago, but from a communication by O. Wallach 2 ) 

 we gather that these suspicions are unfounded. Both from entirely in- 

 active (a) and from commercial (b) menthene, Wallach has prepared 

 J 4 -menthenone from primarily-produced nitrosochloride and has found that 

 both the menthenones possess the same properties: — 



a) B. p. 212 to 213°, d 20 o 0,9165, n D 1,4726; 



b) B. p. 211 to 213°, d 180 0,9170, n D 1,4729. 



From d-menthene nitrosochloride Wallach also obtained a highly- 

 active menthene; the d-menthene had been prepared from menthol ac- 

 cording to Tschugaeff 3 ). The constants of the £-zl 4 -menthenone were as 

 follow: b.p. 211 to 212°, d 18G 0,919, [«] D — 67,46° (14,62 p. c. solution in 

 methyl alcohol), n D 1,4729. Reduction by PaaPs method proved that the 

 ketone with b. p. 211 to 213° was actually a menthenone. In the course 

 of this reaction a ketone was formed which was reducible into menthol 

 (m. p. 39 to 40°). Hence the remarkably low boiling-point of zl 4 -menthenone 

 must have its foundation in the atomic structure of the body. The tertiary 

 position of the isopropyl between carbonyl and an ethylenic carbon bond 



— C:C — C:0 — , would appear to favour the depression of the b.p. 

 • 



C 3 H 7 



CH 3 CH 3 CH 3 CH 3 



A" Ao Ao 



Jo \ ;o 1 J. 



CH (CH 3 ) 2 CH (CH 3 ) 2 CH (CH 3 ) 2 CH (CH 3 ) 2 



(I) J*-Menthenone-3. (II) ^-Menthenone-S. (Ill) Carvenone. (IV) Carvotanacetone. 



r ) Berl. Berichte 41 (1908), 1801 ; 42 (1909), 2408. 



*) Nachr. K. Ges. Wiss. Gottingen 1912. Meeting of 17 th February. 



3 ) Berl. Berichte 32 (1899), 3333. 



11 



