— 90 — 
method into dihydrocarvylamine , and the phosphate of the base 
then distilled dry in vacuo '^). The hydrocarbon thus obtained was 
still contaminated with terpinene, which, however, could be separated 
off as nitrite by nitrous acid. The new menthadiene C;,^o-^i6 farther 
purified by distillation over sodium, has the following properties : boiling 
point: 174° to 176*^ (766 mm); optical rotation: — 3° (tube 200 mm 
long); d^: 0,8441; n: 1,48451. The optical rotation is in the author's 
opinion probably due to a small admixture of limonene, whilst the 
menthadiene itself is inactive. The latter is rapidly destroyed by chromic 
acid mixture, but otherwise is very stable. The author assigns to it 
the following formula: 
H,C 
C. CH3 
CH 
\ 
\ 
CH 
C • C3H7. 
Pulegene. In his sixty first Treatise on terpenes and essential 
oils'^) Wallach reports on pulegenic acid and its derivatives. 
Pulegenic acid C^oH^gOg is formed when pulegene dibromide is 
boiled with a solution of sodium^) in methyl alcohol as much as possible 
free from water. By converting its chloride with aqueous ammonia, 
the amide (melting point 1 2 1 ° to 122°) is obtained, whilst conversion 
with aniline in ethereal solution yields the anilide (melting point 124°). 
The ester of pulegenic acid is very difficult to saponify. If it 
(3 molecules) is oxidised with a i per cent, solution potassium permanganate 
(2 molecules), a bioxyester (melting point 1 18° to 1 19°) is formed, which 
very easily saponifies already during the recrystallisation. If the liquor 
obtained on saponification of the ester is acidified, there is obtained, 
not the dioxyacid, but immediately the oxylactone Qo-^ie^S' which has 
been described previously^), and which is formed by oxidation of 
pulegenic acid. 
The lactone C^^YL^qO^ from hydrochlorpulegenic ester, which has 
also been described some time ago ^), can be obtained in a more simple 
manner by boiling pulegenic acid with dilute sulphuric acid. It melts at 
30^ to 31°, and boils at 126° to 128° (at 12 mm). The same lactone 
is also obtained when hydrobromic acid is attached to pulegenic acid. 
^) Liebig's Annaleii 328 (1903), 90. 
^) Liebig's Annalen 327 (1903), 125. 
3) Report April 1896, 53. 
^) Liebig's Annalen 327 (1903), 125. 
^) Report October 1898, 59. 
