— gl- 
and the reaction-product is boiled with alcohoKc potash. The pulegenic 
lactone H^g differs from pulegenolide C^^QH^^Og^) inasmuch 
as it does not, like the latter, yield an oxyacid capable of existence. 
From this it may be concluded that pulegenic acid lactone is a ^/-lactone. 
Pulegenic acid readily passes over in the distillation, by splitting 
off carbonic acid, into the hydrocarbon pulegene, which has the following 
physical constants: 
boiling point 138° to 139°; d = 0,761; nj)22° = Ij438o. 
Under certain conditions which must be strictly adhered to, it is 
possible to obtain from pulegene a nitroso-chloride (melting point 74"^ 
to 75°) which with piperidine is converted into pulegene nitrolpiperidide 
C9 H-^gNG • NC5H10 melting at 106° to 107°. If hydrochloric acid 
is abstracted from the nitroso-chloride by means of sodium methylate, 
the oxime CgHj^NOH of pulegenone €911^40 is obtained. This 
ketone is split off from the oxime by dilute sulphuric acid. It boils 
b at 189^ to 190°, has the specific gravity 0,914, and at 20^ the 
refraction index 1,4645. Its semicarbazone melts at 183° to 184°. 
Pulegenone absorbs on reduction four hydrogen atoms, and passes over 
into dihydropulegenol C9 H^^g O. This alcohol can be oxidised by 
chromic acid into dihydropulegenone CgH-^gO, which has a menthone- 
like odour, and possesses the following constants : 
boiling point 184° to 185°; d = 0,8875; ^d20° = '^^44^- 
The oxidation of dihydropulegenone, undertaken for the purpose 
of clearing up the constitution, yielded two ketone acids of the same 
composition C9 H-^g03, one of which is converted by further degradation 
with sodium hypobromite into the dibasic a-isopropyl glutaric acid 
CgHj^O^ (melting pomt 94° to 95°), but of which the other is identic 
with the ketone acid obtained by the oxidation of pulegene. This acid 
is formed by shaking pulegene with a five per cent, solution of potassium 
permanganate. It forms a yellowish oil boiling at 164° at 15 mm 
pressure, and yields a semicarbazone as w^ell as an oxime. Its products 
of degradation, obtained by means of chromic acid, are acetone and 
a-methyl glutaric acid. From these results Wallach concludes that 
the constitutional formula nxj 
belongs to the ketone acid. 
In this connection Part IV of the Treatise contains discussions on the 
constitution of pulegenic acid and its derivatives. On the strength of the ex- 
perimental material, the author establishes the following atomic groupings : 
CH3 — CH — CH2 — CH2 — CO — CH 
COOH 
1) Report October 1898, 59. 
