— 127 — 



Methylhexanone. By treating methylhexanone (from pulegone) 

 with sodium amide, and subsequently allowing alkyl iodides to act on 

 the sodium compound of methylhexanone produced, A. Halle r 1 ) has 

 obtained several homologues and one isomeride of menthone. The 

 reaction takes place according to the following equation: 



H 9 H 9 H 9 H 9 



H.CHj( )HNa + IR = H.CH 3 ( >RH + NaI 



H 2 O H 2 O 



All the compounds obtained in this manner yield crystallised semi- 

 carbazones; they also combine with aromatic aldehydes, especially 

 with benzaldehyde. In addition to dimethylhexanone, methylethyl- 

 hexanone, methylpropylhexanont, and methylallylhexanone, Haller, 

 conjointly with Mar tine, obtained in this manner an active menthone 

 which is identic with the menthone obtained by oxidation from ordin- 

 ary menthol. The boiling point lies at 207 to 209 ; « D -\- 1 2° 56' '. 

 The melting point of the oxime is 5 8° to 59 , that of the semi- 

 carbazone 183 to 184 . 



O. Wallach 2 ) communicates a new case of optical isomerism 

 which has become known on the occasion of a work on methyl- 

 hexanone. The methylhexanone obtained by splitting up pulegone 

 is dextrorotatory. It has the specific rotatory power [ a JDi5,3° -f- i-3»33 •• 

 In solution, the rotation depends on the character of the solvent. For 

 instance, with alcohol it is Wdi4° -f~ io>45°; w ^ tn ether Hdi5° -f- 1 7A4°- 

 Pure R-1-methylhexanone oxime, obtained from R-methylhexanone, 

 wiiose uniform character was demonstrated by Wallach, has Hd22° 

 — 42,07°. If this oxime is converted into the benzoyl compound, two 

 modifications can be obtained by fractional crystallisation from ligroin, 

 of which the one rotates to the right, and the other to the left. 



R-d-a-benzoylcyclomethylhexanone oxime (melting point 96° to 97°) 

 is the principal product, and has in ethereal solution Md22° -f- 19,97°. 

 The more readily soluble R-l-/?-benzoylcyclomethylhexanone oxime 

 (melting point 82° to 83°) "has in ethereal solution Wd21° — 86,08°. 



The fact that from one completely uniform oxime two benzoyl 

 compounds of different rotations are obtained, can only be explained, 

 as Wallach points out, by stereoisomerism of the nitrogenous radical, 

 so that the two compounds must be interpreted as syn- and antiform 

 of the benzoylised oxime, and in this manner the optical behaviour 

 of the molecule is influenced one way or the other. 



*) Bull. Soc. chim. III. 31 (1904), 899. 

 2 ) Liebig's Annalen 332 (1804), 337. 



