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Organic Compounds in Fossil Plants (Equisetum; Horsetails).

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The structures of (2a). (2b), and (2d) were proved by mixed
melting points o r mixed chromatograms with authentic
samples and by comparison of the I R spectrar3.71.
Alkyl- and aryl-cyclopropenes are stable under the above
conditions, but o n longer irradiation, parlicularly in rhe
presence of sensitizers, are converted into tricyclohexanes [4,81.
Received: October l l t h , 1967
[Z 634 IEI
German version: Angew. Chem. 79, 1104 (1967)
["I Dr. H . Diirr
lnstitut fur Organische Chemie der Universitat
66 Saarbriicken 1 5 (Germany)
[ l ] Part IV of Photochemistry of Small Rings. - Part 111: H .
Diirr, Liebigs A n n . Chem., in press.
121 W. R. Bamford and T . S . Stevens, J. chem. SOC.(London)
1952, 4735.
[ 3 ] G . L. Closs, L. Gloss, and W. Boll, J. Amer. chem. SOC. 85,
3796 (1963).
[4] H. H. Stechl, Chem. Ber. 97, 2681 (1964).
[5] Diethylene g!ycol dimethyl ether.
[6] W . G. Dauben and F. G. Wiley, 3. Amer. chem. SOC.84, 1498
(1962).
[7] R . Breslow and H . W . Chang, J. Amer. chem. SOC.83, 2367
(1961); R. Breslow and P . Dowd, ibid. 85, 2129 (1963).
[8] H. Diirr, Tetrahedron Letters 1967, 1649.
Organic Compounds in Fossil Plants
(Equisetum; Horsetails) [*I
By H . Knoclte and G. Ourissun [*I
Chemotaxonomic classification of fossil plants would be
particularly interesting since it could be carried out on mutilated and incomplete specimens, and because conclusions
could be drawn about the history of the fossils from comparison of the constituents of fossil and fresh plants.
We have begun experiments designed to isolate organic compounds, in particular hydrocarbons, from fossil plants from
the bunter sandstone of the Northern Vosges (Trias, 2 x 108
years old) and to compare them with the compounds in
present-day plants. Of the fossils available to us a horsetail
Equisetum brongniarti I21 was especially interesting because
numerous Equisefum species still grow today. The stems of
I
280°C
I
250°C
200°C
the plants were approximately 30 mm in diameter. I n addition, horsetails have few parasites 131, which diminishes the
danger of the compounds found originating from foreign
organisms. Great attention was paid t o purity during the
collection, and contamination during working up was excluded by control experiments. The Equisetum described
here came from a clay inclusion in the bunter sandstone Of
the Northern Vosges (Hangvillier, Moselle).
400 g of dried rock containing ca. 20% of fossil plants (further separation from the rock is rather difficult and unnecessary since the surrounding material contains very little
organic material [41) were ground and extracted with 400 ml
of a benzenej'methanol mixture (3: 1 v/v) using a n ultrasonic
technique (25 kHz). Centrifugation, decantation, and removal
of the solvent by distillation gave 3 mg of residue, which was
desulfurized in a small column by 100 mg of active copper
and then separated on 2 g of silica gel (Merck, 0.05-0.2 mm).
Elution with 50 ml of petroleum ether gave the hydrocarbon
fraction (ca. 0.5 mg). The gas chromatogram (Fig. l a ) showed
four main components in the ratio 1 :I : 2.4: 2151.
50 g of fresh, dried Eqzrisetum sylvnticum (wood horsetail) was extracted with 500 ml of benzene (ultrasonically).
The hydrocarbon fraction (18 mg) was isolated from theextract
by column chromatography. The gas chromatogram of this
fraction (Fig. l b ) showed the same four main components
in almost the same proportions, namely, 1 : 1:2.4: 1.3 [ * * I .
The products were identified as the normal hydrocarbons
n-C23H48, n-Cz5Hsz, n-Cz7H56, and n-Cz9Hso by their gaschromatographic retention times [61, mass spectra, and
inclusion in Linde molecular sieves ( 5 p\, 6 h in boiling isooctane). The extract of the fresh plant does not contain the
numerous minor components of the fossil plant.
In this work the same compounds have been isolated for the
first time from a living and a fossil plant and it has been
proved that hydrocarbons can remain unchanged in a fossil
for 200 million years.
Received: October 13th, 1967
[ Z 636 IE]
German version: Angew. Chem. 79, 1107 (1967)
[ * ] Prof. G. Ourisson and Dr. H. Knoche
Universite d e Strasbourg, Institut de Chimie,
Laboratoire attache au C.N.R.S.,
1, rue Blaise Pascal
Strasbourg (France)
[**I Note added in proof: K . Stransky, M . Streibl, and V. Hemiit,
Collect. czechoslov. chem. Commun. 32, 3213 (1967), have
recently found the ratio of alkanes n-CP3: n-Czs:n-Cz7:n-C29 to
be approximately I : I : 3 : 0 . 5 in the wax of fresh Eyuisetum
pcilustre L.
[ I ] Part I. - This work forms part of the research program
D.G.R.S.T. NO. 64-FR-058. -- We thank Messrs. L. Grauvogel
and J.-C. Gail for help in collection of the fossils, and Dr. Vetter,
Hoffman-La Roche, Basel, for determination of the mass spectra.
[2] W. P. Schimper and A . Mougeot: Monographie des piantes
fossiles du gres bigarre der chaine des Vosges. Wilhelm Engelmann, Leipzig 1844.
[3] R. Hegnauer: Chemotaxonomie der Pflanzen. Birkhiiuser,
Basel, Stuttgart 1962, Vol. I.
[4] R. Brandt and G. Ourisson, unpublished work.
[SI Conditions: Perkin-Elmer gas chromatograph 226, 1.5')/, of
SE-30 on Aeropack 30, SO/lOO mesh, 1.80 long, 3 mm in diameter,
program 6.25 "C/min, 100-290 "C, 30 ml of He per min.
161 Perkin-Elmer gas chromatograph 226, capillary column
0.025 mm, 50 m, SE-30, 240 "C, 1.6 mol of He per min; retention
times: benzene 3.9 min., n-Cz, 9.3 min, n-C25 13.5 min, n-CZ7
31 min, n-C29 33.8 min.
Ionization Energies-of Silyl- and
Alkyl-ethylenes [**I
By H. Bock and H. SeidIc*I
1253511
280°C
250°C
200°C
Fig. 1 . Gas chromatograms IS] of the hydrocarbon fractions from (a)
fossil and (b) fresh Eqvisefum.
Angew. Chem. internat. Edit. 1 VoI. 6 (1967)
No. I 2
The differing properties of simple x-electron systems containing R3Si- and R3C-substituents can be considered as being
due t o the different inductive polarization (+Is~R, >
1085
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