— 117 — 
d-menthylamine previously obtained by Wallach is not identic with 
the one obtained in this case, as on treatment with nitrous acid it 
does not yield menthol, but menthene. 
Pulegone, which contains two hydrogen atoms less than the allied 
menthone, could be converted by Beckmann into a new '^iso-laevo- 
menthone", by attaching hydrobromic acid to the double-linking, and 
substituting the bromine by hydrogen by means of zinc dust and 
alcohol. It is a colourless oil, and has the same rotation as the 
well-known 1-menthone. Its oxime, however, does not melt at 59°, 
but at 85°. Boiling point and odour are approximately like those 
of the menthone which can be inverted into d-menthone. All its 
properties show, that it is structurally identic with the menthones 
hitherto obtained. 
As Andres and Andreef showed years ago, 1- and d-menthone- 
oxime yield on reduction 1- and d-menthylamine respectively; Wallach 
and Kuthe obtained from d-menthone, by heating with ammonium 
formate, a mixture of both bases which could be separated by formates. 
More recent examinations by Tutin and Kipping^) show, that the 
hitherto accepted view, that the 1- and d-menthones produced by 
oxidation of menthol with bichromate are optical antipodes, is in- 
correct, as the oximes of both ketones are Isevorotatory, in spite of 
the fact that the latter turn 25° to the left or right. For this reason 
Tutin and Kipping believe that the action of sulphuric acid, accord- 
ing to its strenghth, effects a more or less large racemisation of the 
1-menthone, and they explain this by a partial enolisation, as shown 
by the following formulae in which the minus sign stands for laevo- 
and the plus sign for dextro -rotation : 
CH, — CO CH2— C(OH) 
_/ " \_ _/ \ 
CH3.CH CH — CH(CH,)., CH3.CH C — CH(CH3L 
\ / \ / 
C — C Hg C Hg — C 
l-menthone enol-form 
C — C O 
CH3.C CH — CH(CH3).2 
C H2 — C Hg 
" d- menthone", 
1 - isomenthone. 
1) Journ. Chem. Soc. 85 (1904), 65. 
