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Organic Reactions in the Plasma of Glow Discharges.

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In an heterogeneous system with liquid B 2 0 , the accompanying gaseous phase is, in accord with the supposition
of the method of calculation (sliding equilibrium), in equilibrium with gaseous boron oxides, so that the proportion
of liquid B,O, can be calculated by difference.
If the total composition is known then the enthalpies of
the combustion products at given temperatures and pressures are also known, and an enthalpy-entropy curve can
be plotted after calculation of the respective entropy values.
The thrust chamber isobars each intersect the isenthalpic
lines of the calorific value of the mixture at a point from
which the isentropically assumed expansion occurs.
The intersection of these isentropic lines with the expansion
isobar (e.g. 1 bar under ambient conditions) afford the
enthalpy difference which is convertable into kinetic
energy and from which the emission velocity of combustion
products after having passed the nozzle of the second
thrust chamber can be calculated. For a mixture of boron
air, h= l.lL3],
the discharge rate for an expansion ratio
20: 1 is 1893 m/s, the thrust chamber temperature under a
pressure of 20 bar is 2717"K, and the expansion temperature (20: I)
2070°K.
tions with ring closure, e. g., the reaction of diphenylamine
to give carbazole, and of hydroxybiphenyl to give dibenzofuran illustrate interesting possible applications of plasma
chemistry.
Plasma reactions take place mainly through radicals. The
electrons transfer the energy of the external field to the
molecules. This yields excited molecules, ionized molecules,
or negative ions, which give the products either directly or
after decomposition to radicals. Different mechanisms are
found with individual classes of compound ;some resemble
those of pyrolysis, others those of photolysis or the processes in the mass spectrometer, and yet others have no relation
to known mechanisms.
The reactions of organic molecules in the plasma offer
interesting preparative possibilites. Several processes have
been worked out on a laboratory scale ; application on an
industrial scale is certainly a possibility.
Lecture at Tiibingen on January 22,1971 [VB 284 IE]
German version: Angew. Chem. 83,413 (1971)
+
Lecture at Miinchen on February 14,1971 [VB 283 IEJ
German version: Angew. Chem. 83,412 (1971)
[I] I . Husrnann, Diplomarbeit, Technische Universitat Miinchenl969.
[ 2 ] K.Schadow, A. I. A. A. Journal Vol. 7, No. 10, 1870 (1969).
[3] h = l when equivalent quantities of fuel and oxidizer are reacting;
when h = l . l there is an excess of air. h=coeffcient of oxidizer.
Organic Reactions in the Plasma of Glow Discharges
By Narald Suhr"]
When electrons with an energy of a few eV impinge on
organic molecules, the latter are partially altered and
rearrangements, fragmentations, or, at high pressures,
bimolecular processes can occur. Some of these processes
have long been known but were not suitable for preparative
purposes because in previous work the substances were
largely destroyed with formation of low-molecular gases
and tar. A procedure has now been worked out by which
electron impact processes can be utilized preparatively.
The apparatus is similar to that for vacuum distillation in
which a high-voltage or high-frequency glow discharge is
produced in the vapor space. Simple laboratory apparatus
(with about 100 watts) produce 0.1-1 mole of product per
kWh.
A number ofreactions occur particularly well in the plasma.
They were worked out first with the parent compounds,
but can be extended to substituted compounds. High yields
are obtained in dehydrogenating dimerization, e. g., of
benzene to biphenyl and of methylated aromatic compounds to 1,2-diarylethanes. Rearrangement of alkyl aryl
ethers and N,N-dialkylanilines to respectively, alkylphenols and N-alkyl derivatives of alkylated anilines, and cistrans-isomerizations, are also among favored plasma reactions. Among eliminations, particularly good yields are
obtained in decarbonylations, e. g., of benzophenone to
biphenyl, of camphor to trimethylbicyclohexane, and of
naphthols to indenes, and in decarboxylations of carboxylic
acids and their anhydrides to hydrocarbons. Dehydrogena[*) Prof. Dr. H. Suhr
Chemisches Institut der Universitat
74 Tiibingen, Wilhelmstr. 33 (Germany)
422
New Sulfides of Metals
By Welf Bronger"]
If the binary metal sulfides are considered in relation to
their positions in the Periodic Table it is noticeable that
very marked changes in properties occur near where the
transition metals are inserted. The structure shows this
particularly clearly : thus sulfides crystallize in salt-like
structural types when derived from metals that have empty
or completely filled d shells-to a smaller extent this is
true also for metals with half-occupation- whereas sulfides
ofmetals with partially filled d shells crystallizein structural
arrangements where metal-metal interaction can be recognized. In this connection it appeared interesting to synthesize and study the structure of sulfides that contain both a
main-group metal and a transition metal in ternary compounds.
Sulfides with heavy alkali metals on the one hand and with
d elements on the other, were prepared by reactions in a
melt under an inert gas. The starting materials were
mixtures of alkali-metal carbonates or sulfides, transition
metal, and sulfur. The following phases were thus synthesized :
K2Mn3S4
Rb2Mn,S4
Cs,Mn,S,
KFeS,
RbFeS,
CsFeS,
Rb,Co,S,
cs2c03s,
K2Ni3S4
Rb,Ni3S4
Cs,Ni3S4
K2Pd,S4
Rb,Pd,S,
Cs2Pd3S4
K2PtS,
X-ray investigation of single crystals showed that the
ferrates have a structure characterized by edge-junction of
the sulfur tetrahedra surrounding the iron atoms1'. 21 to
form chains. In the manganates and cobaltates these sulfur
polyhedra were joined by edges two-dimensionally into
layers[3s41.
In the pall ad ate^^^^ and platinateL6'(the structure
of the nickelate is still unknown) the ligands surround the
transition metal in a planar arrangement, and the sulfur
rectangles are joined by sides to give here too either layers
or chains. In general, the structures of these compounds
[*I Prof. Dr. W. Bronger
Institut fur Anorganische Chemie der Technischen Hochschule
51 Aachen, Templergraben 55 (Germany)
Angew. Chem. internat. Edit.
Vol. I0 (1971) J No. 6
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