Notes on scientific research. 



14.'; 



H 2 C 

 OC 



tCH 2 



Menthenone. Some time ago A. Kotz and E. Anger 1 ), in a brief communication, 

 described an o-menthone-5 (methyl- Wsopropyl-2-q/cZohexanone-5), which they had pre- 

 pared by reducing menthenone from Hagemann's ester. According to W. Dieckmann-'), 

 Cj-j 2 this menthone should be regarded as 3-m ethyl -2-iso- 



propyl-o/c/ohexanone-1. Dieckmann assigns to the 

 menthenone from Hagemann's ester the structure of 

 'c-CHg a 3-methyl-2-i9opropyl-c//dohexene-2-one-l, inasmuch 



as, when oxidised with potassium permanganate, it 



3 7 yields a satisfactory return of /-acetobutyric acid 



a-Methyl-^opropylct/^hexene-^one-l. and isobutyr[c add> 



Kotz and Anger state that the semicarbazone of the menthenone from Hagemann's 

 ester melts at 152° or respectively at 138°, the oxime at 90 to 91°, but Dieckmann 

 gives 167 to 168° and 104° respectively. 



A reference to the electrolytic reduction of pulegone will be found on p. 141. 



On the electrolytic reduction of carvone, see p. 141. 



Ion one. A publication by A. Skita ;) ) on hydrogenation with platinum-metals as 

 catalysers contains some interesting data on the reduction of the ionones. «-Ionone, 

 in the presence of palladium chloride and gum arabic in dilute alcoholic solution, was 

 shaken under over-pressure of 1 atm. until the quantity of hydrogen required for the 

 reduction of a double bond had been absorbed. The reduction-product, dihydroionone, 

 boiled between 121 and 122° (14 mm.); it had completely lost its characteristic aroma 

 and only possessed a faint odour of cedarwood. By the same method, /^-ionone yielded 

 a dihydroionone with b. p. 126 to 129° (12 mm.). When the reduction is continued 

 until hydrogen ceases to be absorbed, both «- and /?-ionone yield tetrahydroionone, 

 b. p. 126 to 127° at 13 mm. 



The fact that the reduction of a- and /2-ionone affords two different dihydroionones 

 (I and II) indicates that the extracyclic bond is the first to be dissolved. This agrees 

 with the fact that continued hydrogenation leads to the same tetrahydroionone (III). 



H 3 C 



CH 3 



H 2 C 



CH-OVOVCO-CHi 



H 2 Cv JC-CHs 

 CH 



I. Dihydroionone from a-ionone. 



H 3 C\ /CH 3 HsjC^ / CH 3 



c c 



H,C,/\c-CH 2 CH,,COCH 3 HaC/ NcHCHa-CHaCOCHs 



H 2 Ck ^C-CH 3 H 2 C X /CHCHs 



CH 2 CH 2 



Dihydroionone from ^-ionone. 



Tctrnhvdroiononc. 



x ) Berl. Berichte U (1911), 466; Report April 1911, 182. — 

 Berichte 45 (1912), 3312. 



: ) Berl. Berichte 45 (1912), 2697. 



s ) BaL 



