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Measurement of Vapor-pressure Differences for Isotopic Compounds.

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C O N F E R E N C E REPORTS
Mechanism of the Gomberg Reaction and of
Phenylation by N-Nitrosoacetanilide
The values in the Table were found for the viscosity of AIBr3
(m.p.97.5°C;b.p.2550C)andAI13(m.p.1920C;b.p.386'C).
By Ch. Riichardtc*l
In both cases the exponential function q = A exp (%/RTj
proposed by Andrade121 was followed. For AIBr3, A
3 4 . 5 ~ 1 0 - 3 CP and E-,, = 3.13 kcal mole-1; for AlI3, A =
6 4 . 0 ~10-3 CP and Eq = 3.46 kcal mole-1.
7
Phenylation of aromatic compounds by the Gomberg reaction and by N-nitrosoacetanilide can both be interpreted as
formation and homolysis of diazoanhydrides ( I ) [I].
The key hypothesis for understanding these reactions,
namely, formation of relatively stable diazotate radicals (2),
is supported by chemical and physical evidence.
Polymerisation of styrene initiated by N-nitrosoacetanilide
gives only a small amount of polymer (1 to 2wt- % j containing
nitrogen. The inhibiting action of stable diazotate radicals,
which trap the growing chains, can explain this result. During
the whole period of decomposition of N-nitrosoacetanilide
in benzene an ESR spectrum is observable ( g = 2.0055) that
contains three groups of lines whose fine structure agrees with
the structure of the diazotate radicals. By using IsN-labeling
the N coupling constant a N == 11.61 gauss was assigned to the
"outer" nitrogen atom and a N = 1.67 gauss to the nitrogen
attached to the aromatic group. The spectra of p-deuterioand p-t-butyl-diazotate radicals can be best reproduced by
assuming differing ortho-couplings, accordiiig to which diazotate radicals have a non-linear structure, as has been
assumed also for diazotate anions.
Lecture at Giessen o n January 24th, 1967
[VB 61 IE]
German version: Angew. Chem. 79, 693 (1967)
[*] Priv.-Doz. Dr. Ch. Ruchardt
Institut fur Organische Chemie der Universitiit
Karlstr. 23
8 Munchen (Germany)
[I] Ch. Riichardt, Angew. Chern. 77, 974 (1965); Angew. Chern.
internat. Edit. 4, 964 (1965).
The Viscosity of Liquid Aluminum Halides
By K . H . Grothe and P. Klein~chmit~*l
It is difficult to determine the viscosity of molten salts by the
usual methods if the substances are sensitive to air or have
a high vapor pressure. Such substances include aluminum tribromide and triiodide. A method was therefore chosen in
which a vessel suspended from a wire was made to execute
torsional oscillations, the damping of the oscillations being
measured and used to determine the viscosity. The salts
were distilled into a cylindrical glass vessel of about 3 cm
diameter and 4 cm height and the vessel was subsequently
sealed in a vacuum. The vessel was hung on a torsion wire
and made to oscillate about its vertical axis. The friction
between the layer of liquid adhering to the inner wall and the
liquid near the wall leads to damping of the oscillations.
1 I 1
1
1 1 1 1 1
The viscosities found also follow the equation given by Butschinskil31: v = B q + b, where Y is the specific volume,
9 = l!r, the fluidity, b is the specific volume at zero fluidity,
and B is a constant. The values of b extrapolated from this
equation d o not agree with the specific volumes of the solid
aluminum halides at the melting point but are about 10 "4
greater.
[VB 73 1El
Lecture at Hanover (Germany) on February 23rd, 1967
German version: Angew. Chem. 79,727 (1967)
[*I Dr. K. H. Grothe und Dipl.-Chem. P. Kleinschmit
lnstitut fur Anorganische Chemie
der Technischen Hochschule
Callinstr. 46
3 Hannover 1 (Germany)
[I] E. Helmes in: Ullrnanns Encyklopadie der technischen Chernie. Urban und Schwarzenberg, Munchen-Berlin 1961. Vol. 2/1,
p. 771.
[ 2 ] C. Andrade, Nature (London) 125, 309, 582 (1930).
[3] A. J . Batschinski, Z . physik. Chem. 84, 643 (1913).
Measurement of Vapor-pressure Differences for
Isotopic Compounds
By H . Wolff and A . Hopfner[*l
Replacement of H by D either decreases (normal effect) or
increases (inverse effect) the vapor pressure (p) of a substance.
Hydrocarbons show the inverse effect; alcohols and amines
(including H20 and NH3) show a normal effect insofar as
replacement is at the hydroxyl or amino group, but otherwise an inverse effect.
Study of the vapor-pressure isotope effect for the methylamines CH3NH2 ( I ) , CH3ND2 (Z), CD3NH2 (3), and
CD3NDz ( 4 ) in relation to temperature and concentration
(in mixtures with n-hexane) showed strong, temperaturedependent normal effects for the pairs (I)/(.?) and ( 3 ) / ( 4 ) ,
that change to inverse effects at high dilution (molar fraction
< 0.1). The inverse effects observed for (1)/(3) and (2)/(4)
are only slightly dependent on temperature and independent
of concentration.
It is concluded from the experimental results that appearance
of the normal vapor-pressure isotope effect for the substances
named is connected with the occurrence of association by
hydrogen bonding. Quantitative interpretation seems to be
possible by means of the hydrogen-bond vibrations to which
the translational and rotational degrees of freedom of the
free molecule correspond, though these vibrations are not
readily accessible spectroscopically. For the ideal case of
wholly independent harmonic vibrations the isotope effect of
one degree of freedom is given by
AIBr3
T("C)
'I(CP)
100
150
200
1250
_ _ _ _ _ _ _ _ _ ~ _ _ _
2.37
1.42
0.96
0.71
~11,
T("C)
200
240
300
340
__
400
~~~
r, (CP)
2.62
1.90
Angew. Chem. internat. Edit.
1.32
1.10
Vol. 6 (1967) No. 8
0.86
This formula also explains why all substances show a normal
effect at very low temperatures (< 70 OK), since, under these
conditions, the lattice vibrations (whose characteristic
temperatures mostly lie below 100 "K) may contribute to the
713
vapor pressure isotope effect whereas they are fully excited a t
room temperature and thus d o not contribute.
Lecture at Heidelberg (Germany) on February 28th, 1967 [VB 74 IE]
German version: Angew. Chem. 79,728 (1967)
ment of the equilibrium are suppressed by internal hydrogen
bridges. For instance, the 2-methoxycarbonyl compound ( I )
is a true nitrosophenol both in the solid state and in benzene
or dioxane.
[*I Prof. Dr. H.Wolff and Dr. A. Hopfner
Physikalisch-Chemisches Institut der Universitait
Tiergartenstr.
69 Heidelberg (Germany)
Developments of Fuel Cells
By W. Vielstich [*I
General Motors recently exhibited a bus (Electrovan) driven
by a 32 kW H2/02 battery (Union Carbide Inc.) operating
an alternating current motor. Disadvantages of this experimental model are the tanks containing liquid hydrogen and liquid oxygen (danger of explosion) and the high
cost of the noble metals in the hydrogen electrode. A 200 kW
battery constructed by Firma ASEA, Sweden, for propulsion of a submarine, utilizes ammonia and liquid air;
the ammonia is first cracked in a reformer and the hydrogen
obtained is fed to skeleton nickel electrodes.
The triangular potential scan method is useful for study of
the fundamental principles. In the region between initial
H2- and 02-evolution, the electrode potential varies linearly
with time in a periodic manner. In this way, the experimental
electrode is reproducibly reactivated during measurement.
The nature of the intermediate product in the oxidation of
formic acid is of particular interest. By comparing the
charge needed for oxidation of the adsorbed intermediate
with the amount of carbonate formed (determined by
titration) it was shown that one electron is consumed per
carbon atom. This result suggests that COOH radicals are
the intermediates, rather than CO.
The composition and structure o f the catalyst have a great
effect o n the dehydrogenation of methanol and formate in
alkaline electrolytes. At the same electrode potential the
anodic current densities for methanol (uncharged particles)
and formate (charged particles) on various catalysts (e.g. Pt,
Pd, and Pt/Pd alloys) differ by more than one order of
magnitude.
Fuel cell batteries based on methanol/air and formate/air
and incorporating these catalysts have already been tested as
energy sources in signal installations and TV relay stations.
Fuel monocells are superior to the usual dry batteries
in respect of greater capacity, constant discharge potential,
ease of recharging, and better storage life. Monocells are
constructed o n the following principles: The lid of the
monocell is fitted with a cylindrical carbon diffusion electrode
with an air inlet and a metal terminal. The cell also contains
a cylindrical fuel electrode and fuel electrolyte (20 ml 4 M
C H 3 0 H + 9 N KOH). After discharge (e.g. 50 mA, 0.6 v,
240 h, 12 Ah), the element can be regenerated simply by
renewal o f the electrolyte.
Lecture at Gottingen (Germany) on February 23rd, 1967 [VB 75 IEI
German version: Angew. Chem. 79, 726 (1967)
On the other hand, in the solid state the 3-methoxycarbonyl
compound (2) is a quinone oxime with intermolecular
hydrogen bridges. The oxime group is in the anti-position to
the methoxycarbonyl group, as it is also in other quinone
4-oximes having a substituent on C-3 [21.
5-Methoxy-2-nitrosophenol exists in a brownish-green and
in a n orange form. Burawoy 131 concluded from the electronic
spectra of this compound in various solvents that an equilibrium exists between the nitrosophenol with a n internal
bridge and a quinone oxime with a n internal bridge. Bartindale[4] proved that the orange form in the solid state is a
quinone oxime with intramolecular bridges and anti-relation
of the oxime group to the quinone oxygen atom, which is in
agreement with the behavior of 1,4-quinone oximes [21. By
means of IR and electron band spectra of the two solid forms
and in various solvents, aided by the dependence of the
spectra on the hydrogen ion concentration and on temperature, it has been found that, in carbon tetrachloride, there is
a n o-nitrosophenol with an internal bridge but that in polar
solvents there is a n equilibrium between the nitrosophenol
with an internal bridge, the mesomeric ion, and the quinone
oxime with intermolecular bridges (cf., however 9.
A 1,2-quinone oxime with internal bridge is to be expected
if a substituent in the second neighboring position to the
oxime group prevents the movement of that group from the
syn-position to the quinone oxygen, even though this type of
substitution favors the quinone oxime structure. Such a case
exists in 1,2-naphthoquinone I-oxime; here also polar solvents lead to partial fission of the internal hydrogen bridge,
so that the naphthoquinone with internal bridge is in equilibrium with the mesomeric ion and 1-nitroso-2-naphthol.
Lecture at Hanover (Germany) on February 23rd 1967
[VB 71 IEJ
German version: Angew. Chem. 79, 692 (1967)
[*] Dr. H. Uffmann
Institut fur Organische Chemie der Technischen Hochschule
Callinstr. 46
3 Hannover (Germany)
[l] E. Havinga and A . Schors, Rec. Trav. chim. Pays-Bas 69, 457
(1950); H . Uffmann,Tetrahedron Letters 1966, 4631.
Z. Naturforsch., in press.
[2] H . U’mann,
[3] A . Burawoy et al., J. chem. SOC.(London) 1955, 3727.
141 G. W. R. Bartindale et ai., Acta crystallogr. 12, 111 (1959)
[ 5 ] C. Romers, Acta crystallogr. 17, 1287 (1964).
Investigation of Unstable Molecules and Free
Radicals by Rotational Spectroscopy
[*I Prof. Dr. W.Vielstich
Institut fur physikalische Chemie der Universitlt
Wegelerstr. 12
53 Bonn (Germany)
IntramolecularHydrogen Bridges in Nitrosophenols
By H. U#mann~*I
Tautomeric equilibria of the type p-nitrosophenol 2 1,4benzoquinone 4-monoxime are established via a n intermediate mesomeric ion which can itself play a considerable
part in the equilibrium[ll. Formation of the ion and achieve-
714
By M . Winnewisser[*l
The millimeter and submillimeter region of the electromagnetic spectrum is a field of molecular spectroscopy that
is rich but almost undeveloped. Because of their short
wavelength [lo mm (30000 MHz) to 1 mm (300000 MHz)
these waves can be collimated and focused by a combination
of waveguides, horns, and Teflon lenses, which permits
the use of large glass or quartz absorption cells for spectroscopy of unstable molecules and gaseous radicals [I].
The gases to be studied a-e contained in a cylindrical glass
cell (diameter 10 cm, length 100 cm), which is placed in the
path of the millimeter radiation. A system of gas discharge
Angew. Chem. internat. Edit.
1 Vol. 6 (1967)
No. 8
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