thereby obtained. Especially a solid lactone of the melting point 
79 to 80°, isomeric with pulegenic acid, is formed by that reaction, 
but this lactone is in no way identic with the lactone formed by iso- 
merisation of pulegenic acid itself. Other neutral secondary products 
formed in the production of pulegenic acid, are menthol (in small 
quantity), pulegone, and an unsaturated compound of the composition 
C^oHj^jOg, which appears to have neither an alcoholic, nor a ketone- 
like character. 
Tetrahydrocarvone. In the isomerisation of tetrahydrocarvoxime 
with sulphuric acid, there is formed, as Walla ch showed some time 
ago, a compound CiqI^^qON melting at 104^, which can be readily 
split up into an amidoacid C^oHgiOgN of the melting point 201 to 
202°. Wallach^) has recently succeeded in clearing up the consti- 
tution of this compound, which he did in the following manner: If, 
namely, the amidoacid is treated with nitrous acid, an oxyacid is 
formed, which is converted by loss of water, partly into an unsaturated 
acid (decylenic acid) and partly into a lactone, both corresponding to 
the composition Cj^QH^g02. If the oxyacid is oxidised, a ketonic acid 
of the same carbon-content is obtained, and this ketonic acid is identic 
with the one which A. v. Baeyer obtained in splitting up tetrahydro- 
carvone. On further oxidation this ketonic acid yields an isopropyl 
glutaric acid. 
Only an acid of the formula 
^CH2.C02H 
Ho C . CHfNH,) . CH, . CH. • CH < ^ ^ 
' V 2; 2 2 CH(CH3)2 
can give such products of degradation. 
The position of the ethylene-linkage in decylenic acid was ascer- 
tained in a corresponding manner; to the latter belongs the formula: 
H3 C . CH : CH . CH, . CH<^^^ ' ^ 
CH(CH3)2. 
If, however, the amidoacid has the above-mentioned formula of a 
^-isopropyl-g-amidoheptylic acid, it follows that for the isoxime (melting 
at 104°) of tetrahydrocarvone, only the following is possible: 
H3C.CH<^^''^°*^^^>CH.CH(CH3)2 
C Hg C H2 
Menthone. Leser^) has successfully accomplished a synthesis 
of menthone. By introducing the isopropyl group into acetyl-4-methyl- 
^) Liebigs Annalen 323 (1902), 323. 
^) Compt. rend. 134 (1902), 1115. 
