LAUEACE^E 161
berg^1 who have isolated a fraction boiling at 130° to 150° at 10 mm.,,
which contained a new sesquiterpene which the authors have termed
sesquicamphene and which has the following characters:—
Boiling-point at 8 mm 129° to 133°
Specific gravity. 0-9015 at 20°
Optical rotation ........ +3°
Refractive index 1-50058
It is a bicyclic compound.
They also isolated a sesquiterpene alcohol from the fraction boiling
at 150° to 170° at 10 mm., which on dehydration yielded a hydrocarbon
of specific gravity 0
- 9138 at 20°, optical rotation + 50° and refractive
index 150895. This alcohol has been named sesquicamphenol.
The highest-boiling fractions of the oil, after being heated over
sodium, yielded a hydrocarbon fraction with boiling-point 180
°
to 190°
(11 mm.). Hydrochloric acid gas in ethereal solution was passed through
this fraction, when it afforded a tetrahydrochloride melting-point 129°
to 131°. The hydrocarbon which was regenerated from the hydro-
chloride possessed the following characters: boiling-point 177° to 178°
(6 mm.); d2o° 0-8870; aD ± 0; n 1-50339. Combustion showed the
formula to be C 20 H 32 ; the value (90'6) found for the molecular refraction
also agreed with the formula Co0H 32 /^ (9048). This body, therefore,
is a monocyclic diterpene, which has been called a-camphorene by the-
authors. Regenerated, a-camphorene again formed a hydrochloride
melting-point 129° to 131°. Upon being reduced with platinum and
hydrogen by the usual method, a-camphorene yielded octahydro-a-
camphorene, C 20 H 40 , boiling-point 174° to 176° (9 mm.); WD 146470.
In addition to a-camphorene the highest-boiling camphor-oil fractions
contain a second diterpene, to which Semmler and Rosenberg have
given the name of /?-camphorene. This camphorene can be regenerated
from the oily residues which are formed in the process of preparing
a-camphorene tetrahydrochloride. This diterpene has the following con-
stants: boiling-point 170° to 180° (7 mm.); ^ 2 q^ 0'930 [a]D ± 0; molecular
refraction found 8861; calculation for C 20 H 32 / ^ 8877. Its hydrochloride
remains liquid.
It is a surprising fact that a-camphorene is capable of being built up
synthetically with comparative ease. In order to accomplish the syn-
thesis, Semmler and K. G. Jonas 2 heated myrcene for four hours in a
sealed tube to 250° to 260° by which they obtained a yield of 50 per
cent, of a fraction with boiling-point 175° to 195° (8 mm.) which afforded
a solid hydrogen chloride additive product, melting-point 129° to 130°.
When mixed with a-camphorene tetrahydrochloride obtained from the
blue camphor oil, the melting-point of this body was not depressed;
hence the synthetic hydrocarbon is identical with a-camphorene.
Semmler and Jonas have carried out another interesting synthesis
by heating a mixture of myrcene and isoprene in a sealed tube to 225°.
The result was a yield of about 30 per cent, of a hydrocarbon, boiling-
point 125° to 135° (8 mm.): d 18 o 08685; aD ± 0 ;ji» 1-49166; molecular
refraction found 6810; calculation for C 15 H 24 /~ 6786. This body is
without doubt a sesquiterpene and is perhaps identical with bisabolene.
Its trihydrochloride melts at 83°, but when it is mixed with bisabolene
trihydrochloride the melting-point is depressed by 12°. There is na
lBerichte, 46 (1913), 768. *Ibid., 1566. Schimmel's Report, Oct., 1913.
VOL. I. 11
