NOTES ON SCIENTIFIC RESEARCH. 85 
with zinc chloride or dilute suphuric acid led to p-cymene; the addition of water by 
shaking with 5 p.c. sulphuric acid, to a hydrate, CioHisO2, melting at 132 to 133°. 
The fact that pure limonene, and especially that obtained from caraway oil, when 
exposed to the air, soon again takes the smell of the raw material, can easily be 
explained by the autooxidation of carveol into carvone. 
Effect of high temperatures on sesquiterpenes. 
Many experiments, carried out by F. W. Semmler and W. Jakubowicz‘), have proved 
that it is possible to break down sesquiterpenes into terpenes, and probably, into 
isoprene. Isoprene cannot be determined as such, but its condensation products can. 
When breaking down @-gurjunene, the presence of terpinene could be proved. 10g. 
of gurjunene were heated to 330° for about 12 hours in a sealed tube, when 12 p.c. 
of a substance were obtained, which boiled at from 60 to 65° (10 mm.) and was 
recognized as «-terpinene by means of its nitrosite (m.p. 154°). Further, in addition 
to unaltered gurjunene, dipentene was present, which had resulted presumably by the 
addition of primarily formed isoprene to gurjunene. On breaking down ¢-gurjunene, a 
terpene formed, of which no solid derivatives could be obtained. The fraction which 
boiled highest was a blue oil, representing perhaps an oxidation product of gurjunene. 
Similar blue oils have repeatedly been observed when distilling essential oils. On 
breaking down cedrene, it was likewise impossible to prove the presence of a terpene 
by means of solid derivatives. Caryophyllene furnishes perhaps a terpene allied to 
pinene as well as a diterpene; cadinene, presumably a monocyclic sesquiterpene. 
F. W. Semmler and K. G. Jonas?) report on some derivatives of sesquiterpenes and 
diterpenene, as well as on synthetical experiments in this domain. On a former 
occasion®) they had obtained octahydro-«-camphorene, as a liquid boiling between 
174 and 176° (9 mm.); np 1,46470. On repeated hydrogenation of «-camphorene, they 
now obtained an octahydro-«-camphorene boiling between 183 and 186° (14 mm.); 
dooo 0,8341; a +09 np 1,46001. 
They also report on the bicyclic diterpene iso-a-camphorene. If myrcene is poly- 
merized, a diterpene fraction forms, which yields liquid products on being treated with 
gaseous hydrochloric acid. The authors succeeded, by elimination of hydrogen chloride, 
in arriving at a hydrocarbon, for which they propose the name of iso-ec-camphorene. It 
was likewise possible to produce this body by inverting «-camphorene with sulphuric 
and glacial acetic acid. The constants of this diterpene are: b.p. from 193 to 197° 
(19 mm.); de10 0,9029; npw»0 1,50300. The reduction with platinum and hydrogen furnished 
hexahydroiso-¢-camphorene: b. p. 180 to 186° (14 mm.). 
By heating /-e- and d-$-phellandrene, «-pinene, 6-pinene, and limonene (the last- 
named in the presence of sulphuric and glacial acetic acids) in a sealed tube, diterpenes 
were obtained, which did not afford any solid addition products with hydrochloric acid. 
Some oxygenated terpene bodies, which were heated in a sealed tube, together with 
a dehydrating agent served for further synthesizing experiments. In this way 
a-camphorene formed from linalool; from citronellal, an oxide of the diterpene class, 
CroHzs0, b. p. 190 to 200° (17 mm.). The reduction with platinum and hydrogen yielded 
the corresponding saturated body, CooHssO. 
Cycloisoprene-myrcene*) can be reduced by means of platinum and hydrogen to 
hexahydroisoprene-myrcene. 
1) Berl. Berichte 47 (1914), 2252. — %) Berl. Berichte 47 (1914), 2077. — *) Comp. Report October 1913, 
35. — *) Comp. Report October 1913, 35. 
