— 142 

 against the tautomeric diketo form: 



/ N 



CH 

 H 9 C/ \ CO 



XH a 



CH, 



H 9 C 



CO 



CH-CH, 



But the production of a diosphenol reacting as a diketone has not 

 yet succeeded. Derivatives of diosphenol which have been produced, 

 are p-menthane-diol-2, 3 (b. p. 135 to I37°at 1 o mm. pressure) obtained 

 by reduction of diosphenol with sodium and alcohol, and the dibromo- 

 derivative C 10 H u Br 2 O 2 . — In synthetising diosphenol, Semmler and 

 M c K enzi e started from hydroxymethylene-menthone, which was oxidised 

 into the diketone, and in an acid medium was already partly inverted 

 into the enolic form. The inversion is completed in alkaline or acid 

 solution. The reaction-mechanism may be illustrated by the following 

 graphic formulae: — 



CH< 



,CH, 



CH, 



CH 



/ 



CH, 



CH< 



CH, 



rCIL 



CH, 



CH 



CH 



CH 



H C 



H C 



\co 



C:CH-OH 

 CH-CH, 



H C 



H C 



H C 



H C 



hydroxymethylene-menthone 



(b.p. 120 [11 mm. pressure] ; 



d 20 ° 0,994 ; n D 1,49668) 



The oxidation of hydroxymethylene-menthone with ozone in aqueous 

 solution gives a still better yield, but a certain amount of care must 

 be observed as the oxidation is easily carried too far. The synthetic 

 buchu camphor was identical in its properties with the natural one. 



Suberone. Since v. Baeyer's assumption that tetrahydroeu- 

 carvone should be regarded as trimethylsuberone, must be accepted as 

 established by Wallach 1 ), the latter 2 ) now proposes the following way 

 for producing substituted cyclic heptenones and heptanones, with the 



*) Liebig's Annalen 339 (1905), 97; Report October 1905, 113. 

 2 ) Liebig's Annalen 345 (1906), 139. 



