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Heterogeneously Catalyzed Gas-Phase Bromination of Trifluoromethane.

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Heterogeneously Catalyzed Gas-Phase Bromination
of Trifluoromethane"'
By Hans Bock, Jan Mintzer, Jorg Wittmann, and Jurgen
Dedicated to Professor Rorf Sammet on the occasion of his
60th birthday
Owing to its suitability as a highly effective fire-extinguishing medium in automatic extinguishing installations for
the protection of valuable
considerable interest attaches to a facile preparation of trifluorobromomethane. One
possible pathway is the gas phase bromination of trifluoromethane:
+ Br2 + F,CBr + HBr
Useful yields of ca. 70% are obtained in the thermal reaction
only above about 600"C13.41(cf. Table 1); however, undesired side-products are formed at such high temperatures and
corrosion problems also occur. Experiments with catalysts[51
have so far failed to give improved yields at lower temperatures.
Optimization of the heterogeneously catalyzed gas-phase
bromination (1) was accomplished in three steps:
1) On the basis of the partly publishedI6Iand not completely overlapping photoelectron spectra of the reactants F3CH
and Br, and those of the products F3CBr and HBr (Fig. la), a
gas-analytical technique could be worked out for mixtures of
any c o m p o ~ i t i o dwhich
~ ~ , permits continuous monitoring of
all components of the four-component system.
2) The catalyst screening-fast and with small sample
quantities [',*]-was by PE spectroscopy (Fig. Ib): determining at what temperature the same result is obtained as in the
thermal reaction (e.g. in a tube packed with quartz rings, see
Table 1). The gas-analytical approach chosen also proved
advantageous, in that fluorination of oxide support material
such as SiO, and y-A1203occumng mainly at high temperature can be recognized from the appearance of the characteristic ionization bands of H 2 0 (12.6 eV), C 0 2 (13.8 eV), and/
or CO (14.0 eV)l6].
3) Conversion and yield under reaction conditions optimized by PE spectroscopy are determined at atmospheric pressure on a preparative scale by conventional analysis: after
passage through the heated catalyst compartment the excess
of Br, is condensed out of the gas mixture; the bromine balance (% conversion) is established by addition of the bromine to cyclohexene. HBr is subsequently absorbed in I N
NaOH, back titration gives the yield (%). The F3CH/F3CBr
ratio in the residual gas is determined by gas chromatography.
Table 1. Yield of F3CH bromination according to Eq. (1)as function of catalyst,
furnace temperature T, and contact time I,,.,,,,.
C 450
Quartz rings
Activated charcoal
I Ri
Is1 la1
CuCIdactivated charcoal
FeClJactivated charcoal
KBr/activated charcoal
FeCIJKBr/activated charcoal [b]
[a] Conventionally defined as 1/11 gas/time-l catalyst]. [b] See procedure
Table 1 shows that the thermal gas-phase bromination in a
tube packed with quartz rings at 600 "C affords yields up to
72% depending upon the contact time; prolonged residence
times promote decomposition reactions. Activated charcoal
is ineffective, but is suitable as an inert carrier under the
reaction conditions. Metal salts such as CuC12 and FeC13 catalyze the reaction, while KBr acts as a promoter.
Fig. 1. a) PE spectra of reactants Br, and F,CH and the products HBr and
F3CBr. The bands are seen not to overlap completely. The two double needles
assigned to spin/orbit coupled states each of Brim and HBr-" [6]are particularly
suitable for gas analysis. b) Bromination of FzCH over a CuCl,/active charcoal
catalyst as function of temperature: The 1 :1 mixture (25"C) reacts above 350 "C.
The Br2 double peak at 10.6/10.9eV disappears and that of HBr appears at 11.7/
12.0 eV. At the same time, the first F,CH band at 14.8 eV is replaced by the second one of F3CBr at 14.3 eV.
Prof. Dr. H. Bock, DipLChem. J. Mintzer, Dip1.-Chem. J. Wittmann
Institut fur Anorganische Chemie der Universitat
Niederurseler Hang, 0-6000 Frankfurt am Main 50 (Germany)
Dr.J. Russow
Hoechst Aktiengesellschafi
D-6230 Frankfurt am Main 80 (Germany)
Angew. Chem. Inl. Ed. Engl. 19 (1980) No. 2
FeC13/KBr/C catalyst: HCl is passed over activated charcoal (30 g; Alfa 88765/28 mesh) at 150 "C for 1 h. After cooling in a stream of HCl, the substrate is impregnated with anhydrous FeC13 (5.6 g; corresponding to about 6% Fe on the
camer) and KBr (0.6 g) in CH30H (0.6 g). After stripping off
the solvent in vacuo in a rotatory evaporator, the material is
fluorinated in a stream of F3CH (1/2 h at 30"C, 1 h at
280"C, 2 h at 300°C, 3 h at 350"C, and finally 5 h at
450°C). It is important that the temperature be raised very
slowly between 280 and 320°C owing to transformation of
FeC13 (m.p. 304°C) into FeF3 (m.p. 1030°C).
Received: December 3, 1979 [ Z 393 IEJ
German version: Angew. Chem. 92, 136 (1980)
0 Verlag Chemie, GmbH, 6940 Weinheim, 1980 05700833/80/0202-0147 $ 02.50/0
[I] Analysis and Optimization of Gas-Phase Reactions, Part 16.-Part 15: B. Solouki, P. Rosmus, H. Bock, G. Maier, Angew. Chem. 92, 56 (1980); Angew.
Chem. Int. Ed. Engl. 19, 51 (1980).
121 Cf., e.g., K. Weissermel, H.-J. Arpe: Industrielle Organische Chemie. Verlag
Chemie, Weinheim 1976, p. 51.
131 T. J. Brice, J. Am. Chem. SOC.68, 968 (1946).
141 I. Yuichi, K. Kazuharu, Jap. Pat. 7762208 (1977); Onoda Chem. Co.; Chem.
Abstr. 87. 133857 (1977).
[SI K. Norihisa, I. Fumio, M. Kimiaki, Jap. Pat. 7834705 (1978); Central Glass
Co.; Chem. Abstr. 89, 540 (1978): max. conversion achieved on CrCI,/AIFJ
A120, was 57% at 450°C (cf. Table l).
161 Cf. collections of spectra, such at that of D. W. Turner, C. Baker, A . D.Baker,
C. R. Brundle: Molecular Photoelectron Spectroscopy. Wiley-Interscience.
London 1970.
171 Cf. H. Bock, B. Solouki. .
Wittmann. Angew. Chem. 90,985 (1978); Angew.
Chem. In!. Ed. Engl. 17, 932 (1978); H. Bock, B. Solouki, G. Bert, T. Hirabayashi, S. Mohmand, P. Rosmus, Nachr. Chem. Tech. Lab. 26. 634 (1 978).
181 Cf. also H. Bock, B. Solouki, J. Wilfmann,H:J. Arpe, Angew. Chem. 90, 986
(1978); Angew. Chem. Int. Ed. Engl. 17,933 (1978).
Ullmanns Encyklopadie der technischen Chemie [Ullmann’s
Encyclopedia of Industrial Chemistry). Editorial board E.
Bartholome, E. Biekert, H. Hellman, H. Ley (deceased), W.
M. Weigert (deceased), and E. Weise. Volume 17: Milchsaure to Petrolkoks. Verlag Chemie, Weinheim 1979. 4th
edition, xv, 733 pages, bound, DM 425.00.
The individual volumes of Ullmann’s fourth editionl’l are
appearing with admirable regularity. A scan through this
particular volume confirms that Ullmann is a genuine encyclopedia, going beyond the specific realm of industrial chemistry to deal with the necessary foundations and to include
related fields. Individual overlapping entries treat special areas, such as the “oxidation” entry in the present volume,
which describes in summary the oxidation processes for the
preparation of organic intermediates; the many references to
other entries for further information on certain processes are
particularly valuable. To name some of the volume’s entries
taken from the sphere of inorganic chemistry, we have molecular sieves (10 pages), molybdenum (28 pages), sodium
(87 pages), nickel (64 pages), and niobium (12 pages), including their compounds and alloys (especially important compounds such as sodium chloride and sodium hydroxide have
their own entries), nitrides (7 pages), oxide ceramics (15
pages), and peroxo compounds (38 pages). From organic
chemistry there are lactic acid (7 pages), naphthalene and
derivatives (50 pages), aliphatic (10 pages) and aromatic (6
pages) nitriles, nitroso compounds (7 pages), aliphatic (10
pages) and aromatic (34 pages) nitro compounds, optically
active compounds (7 pages), oxalic acid (8 pages), and peroxides and peroxy acids (30 pages). From the sphere of dye
chemistry we can quote naphthalimide dyes (6 pages), naphthoquinone and benzoquinone dyes (5 pages), nitro and
nitroso dyes (9 pages), and optical brighteners (15 pages),
and from the sphere of pharmacology anesthetics (7 pages),
nucleic acids and their derivatives (6 pages), and parasitoses
(8 pages). Interested in fossil fuels? There are 14 pages on oil
sands, 14 on oil shale, 5 on petroleum coke, and 20 on motor
fuels; this last entry is restricted to gasoline, as diesel and turbine fuels are discussed under fuel oils. In addition, the following application-oriented entries should be mentioned:
perfumes (5 pages), furs (9 pages), nitrocellulose (12 pages),
and in particular paper, subdivided into fibrous raw materials (46 pages) and manufacture (59 pages).
[‘j Cf. Angew. Chem. In!. Ed. Engl. 18.491 (1979)
The present volume is the equal of its predecessors in quality of presentation and material. This is undoubtedly due in
essence to the editors’ efforts in finding competent authors
for the wide range of topics and then in coordinating their
Ulfert Onken [NB 497 IE]
The Chemical Applications of Transmission Electron Microscopy. J. R. Fryer. Academic Press, London 1979. x, 286
pages, 126 figures, 4 tables, bound, $ 38.00.
The present monograph treats the principles of image formation and image contrast in an electron microscope, microscope attachments, specimen preparation, high-resolution
microscopy, and phase contrast, as well as the study of surface phenomena, crystal structures, and precipitates from solutions. The fascinating possibility of a n in-situ observation
of a chemical reaction in a n electron microscope is considered in the last of the eight chapters. The book gives a good
balance between theory and empiricism, the current state of
the art in high-resolution microscopy being emphasized in
preference to the physical principles of electron optics. The
examples have been taken mainly from the author’s own
work. It is rather unfortunate that the technical details are
explained predominantly for the example of the Siemens apparatus used in Glasgow, especially as Siemens no longer
produce electron microscopes.
On the subject of high resolution, supplementary information would be desirable in a new edition, such as data on
structural features that favor the use of this method and a
more extensive discussion of the studies on oxides, in which
the most recently published, higher-resolution pictures are
taken into consideration. The table of the graphite compounds requires revision: it contains many printing errors
and does not correspond to the current state of the art.
It was the author’s intention that the bibliography should
provide information on the work of other authors on subjects
treated in less detail here. T o achieve this aim revision is necessary to include further authors, such as S. Andersson and L.
Finally, it should be emphasized that the book is a handy
and practically-oriented summary with emphasis on providing a really useful introduction to the field, up to now not
easily available to those who wanted to familiarize themselves with the methods of transmission electron miscroscoPY.
Reginald Gruehn [NB 494 IE]
0 Verlag Chemie, GmbH. 6940 Weinheim, 1980 0570-0833/80/0202-0148 $02.50/0
Angew. Chem. Int. Ed. Engl 19 (1980) No. 2
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heterogeneous, trifluoromethyl, gas, phase, bromination, catalyzed
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