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Mechanism of the Gomberg Reaction and of Phenylation by N-Nitrosoacetanilide.

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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
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nitrosoacetanilide, reaction, mechanism, phenylation, gomberg
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