— 132 — 



m. p. 1 3 9°. By treating it with hydrohalogen he also succeeded in 

 preparing the di-hydrochloride (m. p. in to 112 ) and the di-hydro- 

 bromide (m. p. 120 to 12 1°). 



Menthone. We desire to give some further particulars of a paper 

 by O. Wallach 1 ) to which reference has already been made in our 

 last Report 2 ). A synthesis of i-menthone was carried out in the 

 following manner. By condensing 1, 4 -methyl cyclohexanone with 

 bromo-isobutyric ester and further treating the product by the method 



frequently described, a hydrocarbon CH 3 — <^ \ = C = C (C H 3 ) 2 was 



prepared and inverted into i-menthene 3 ). The i-menthenone obtained 

 therefrom by means of its nitroso-chloride was then reduced to i-menthol 

 and from this i-menthone was obtained by oxidation. The semicarbazone 

 of this compound melted at 210 to 212 , the oxime at 77 to 79 . 

 Hereby its identity with i-menthone obtained from 1, 3, 4-trihydroxy- 

 terpane in the sequence of reactions already described, was demonstrated. 

 Further, by brominating zl 4 -menthenone, a dibromide (m. p. 3 6°) 

 was obtained, while reduction yielded a not entirely congealing menthol 

 which obviously contained a mixture of stereoisomeric menthols. The 

 presence of i-menthol could be proved by oxidising the substance to a 

 ketone, from the semicarbazone of which portions of 210 to 2i2°m. p. 

 could be isolated. Up to the present nothing has yet been determined 

 as to the nature of those fractions of the semicarbazone which have 

 a lower melting point. 



E. Beckmann 4 ), has continued, in collaboration with E. M tiller 

 his researches into the optically active menthones, to which we briefly 

 referred at the time 5 ). It is known that 1-menthone, Mr> — 28,5°, 

 which had been previously obtained from natural 1-menthol by oxi- 

 dation with chromic acid mixture, could be converted with cold 9O°/ 

 sulphuric acid into a dextrorotatory isomer, [«]p -\- 28,1°. The original 

 surmise that notwithstanding the equal degree of rotation, this case was 

 not one of a simple optical antipode of the original ketone, was con- 

 firmed in the sequel by the isolation of a strongly dextrorotatory 

 ketone, d-isomenthone, from the mixture with unaltered 1-menthone. 

 From a mixture of several isomeric mentholes which occur in the 

 process of reducing 1-menthone or inverted d-menthone, a d-isomenthol 

 (m. p. 78 to 8i°; t«] D -{-- 2,03°) was also obtainable and from this, 

 again, d-isomenthone, [«]d up to -f-35,1 . Reduction of the oximes 



*) Liebig's Annalen 302 (1908), 261. 



2 ) Report November 1908, 180. 



3 ) Report October 1906, 114. 



4 ) Berl. Berichte 42 (1909), 846. 

 8 ) Report April 1904, 116. 



