— n8 — 



chemical and chemical isomerisations occur, so that the final pro- 

 ducts no longer correspond to secondary, but to tertiary menthol. 

 But in Kondakow's opinion, the assumption of an intermediary for- 

 mation of d-menthol does not yet explain this fact satisfactorily. A 

 more recent examination of d-menthol which Kondakow 1 ) had 

 produced by reduction from the ketone contained in oil of buchu 

 leaves, has, namely, shown that this body, contrary to the opinion held 

 up to the present, is not by any means unstable. Its haloid anhydrides 

 are all dextrorotatory. In producing them, isomerisations take place — 

 as in the case of 1-menthol — , and there occur consequently stable, 

 dextrorotatory, genuine derivatives of d-menthol, as well as unstable 

 derivatives belonging to the tertiary menthol. Menthene, obtained from 

 1-menthol, is dextrorotatory. Different from Kondakow's d-menthol 

 is the isomenthol of Beckmann 2 ), which is formed jointly with 

 d-menthol, when either 1- or d-menthone is reduced. 



Isomenthol is dextrorotatory, and differs from d-menthol by a 

 higher melting point (83,5 to 84 °) and a lower specific rotatory power 

 (Wd -f- 2 5>°4° to 27,07°). On oxidation it is converted into d- 

 menthone 3 ), which forms a dextrorotatory oxime. Although a more 

 detailed examination of isomenthol and its derivatives is still wanting, 

 it may be concluded, in view of its optical behaviour, that in respect 

 of the stereochemical configuration of its molecule, it occupies an 

 intermediary position between the two first menthols, with an approach 

 towards d-menthol. Another 1-isomenthol which would approximate 

 more towards the 1-antipode is not yet known, but can possibly be 

 produced by means of reduction from iso - 1 - menthone. There are 

 further* known three inactive menthols. One of these was obtained 

 by Kremers 4 ) from optically inactive menthone. It melts at 29 to 

 31°, and may possibly be identical with the /?-thymomenthol of the 

 melting point 27° and boiling point 2 17° obtained by Brunei 5 ) from 

 thymol. The second was produced by Beckmann 6 ). Baer 7 ) found 

 a third liquid inactive menthol, which, however, according to its 

 physical properties and chemical behaviour, stands closer to the terti- 



*) Journ. f. prakt. Chemie II. 63 (1901), 49; Report April 1901, 14. 



2 ) Journ. f. prakt. Chemie II. 55 (1897), 14; Report April 1897, 53. 



3 ) According to tests by Skworzow, d-menthone ([a]r> -f- 26,91°), when 

 treated with ammonium formate, also yields formyl-d-menthylamine of the m. p. 117 

 to n8° [a]o + 154,47°, with little 1-amine. 



4 ) Amer. chem. Journ. 18 (1896) 762; Report October 1896, 54. 



5 ) Compt. rend. 140 (1905), 252; 137 (1903), 1268; Bull. Soc. Chim. III. 

 33 (1905), 269; 34 (1905), 500; 35 (1905), 569; Report April 1905, 103; 

 October 1905, 103. 



6 ) Journ. f. prakt. Chem. II. 55 (1897), 30; Report April 1897, 53. 



7 ) On the synthesis of an inactive menthene. Thesis, Leipzig 1898; Report 

 October 1898, 56. 



