ISSN 0012-5008, Doklady Chemistry, 2007, Vol. 412, Part 1, pp. 22–23. © Pleiades Publishing, Ltd., 2007.
Original Russian Text © E.E. Grinberg, V.I. Rakhlin, A.A. Petrova, M.G. Voronkov, I.E. Strel’nikova, S.G. D’yachkova, 2007, published in Doklady Akademii Nauk, 2007,
Vol. 412, No. 3, pp. 351–352.
CHEMISTRY
Synthesis of Phenylmagnesium Chloride in Hydrocarbons
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E. E. Grinberg , V. I. Rakhlin , A. A. Petrova , Academician M. G. Voronkov ,
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I. E. Strel’nikova , and S. G. D’yachkova
Received June 2, 2006
DOI: 10.1134/S0012500807010077
Phenylmagnesium halides are widely used for the iodine [7], metal alkoxides [8], and tetraethoxysilane
introduction of phenyl groups into molecules of organic [9]. However, until now, no reliable and industrially
and organoelement compounds. In spite of the higher feasible method for preparing phenylmagnesium chlo-
reactivity and the ease of preparation of phenylmagne- ride in hydrocarbons has been available. At the same
sium bromide as compared with phenylmagnesium time, the preparation of aromatic Grignard reagents in
chloride, the use of the latter is much more preferable. hydrocarbons offers new possibilities for their commer-
This is due to the substantially lower cost and greater cial application taking into account the low cost, low
availability of the initial aryl halide and the lower pro- hygroscopicity, and safety of these solvents [10].
pensity of phenylmagnesium chloride to undergo the
The use of gallium trihalides as catalysts of different
Wurtz reaction.
processes was proposed previously for preparing orga-
Ether is the most widely used solvent for preparing
nometallic and organoelement compounds. Their cata-
Grignard reagents; however, the reaction of chloroben-
lytic activity was shown to be sharply different from the
zene with magnesium in this solvent proceeds so slowly
activity of similar aluminum and indium salts [11, 12].
that its use for preparation purposes is inexpedient. As
Recently, Japanese researchers also demonstrated that
a rule, the synthesis of phenylmagnesium chloride is
gallium trichloride differs dramatically in reactivity and
carried out with the use of solvents with higher donor
catalytic activity from aluminum trichloride [13].
ability, tetrahydrofuran [1] and ethyl cellosolve [2];
Therefore, we studied the possibility of using gallium
however, their use is limited by their high cost, fire risk,
trihalides as catalysts for preparing phenylmagnesium
and explosion hazard.
chloride in a hydrocarbon medium. The addition of
−4
The method of synthesis of these Grignard reagents
in hydrocarbons with addition of donor solvents is
widely used, in particular, for preparing phenylmagne-
sium chloride in chlorobenzene with addition of tet-
rahydrofuran [3, 4]. However, in our opinion, such an
approach is a certain compromise.
1
0 mol % GaX (X = Cl, I) into the reaction medium
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makes it possible to obtain phenylmagnesium chloride
in aliphatic (nonane) and aromatic (xylene) hydrocar-
bons, narrow cuts of petroleum products (kerosene),
and excess chlorobenzene. The reaction has a short
induction period and starts at 120–125°C. The begin-
Phenylmagnesium chloride can be obtained by the ning of the reaction can easily be detected from a sharp
reaction of magnesium with excess chlorobenzene in an change in the color of the reaction mixture from color-
autoclave at 160–170°C in about 70% yield; however, less to beige or bright yellow. The reaction is completed
this method is poorly applicable in industry [5]. The in 25–30 min on account of the inherent exothermic
synthesis of phenylmagnesium chloride was also facil- effect to result in complete magnesium dissolution. We
itated by the assistance method when a mixture of chlo- did not determine directly the yield of the Grignard
robenzene with ethyl bromide was used [6]; however, reagent. However, it is rather high because the addition
the yield of the compound was only 39%. Different of dimethyldichlorosilane to the reaction mixture leads
additives have been used to promote the reaction: to dimethyldiphenylsilane in 75–80% yield. Below, we
describe a typical example of the reaction procedure.
A 12-g sample of magnesium (0.5 mol), 250 mL of
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chlorobenzene, and 10 mg of gallium trichloride were
Research Institute of Highly Pure Chemical Substances
and Chemicals, Bogorodskii val 3, Moscow, 107076 Russia placed into a three-necked flask equipped with a
mechanical stirrer, a dropping funnel, and a reflux con-
Favorskii Institute of Chemistry, Siberian Division,
Russian Academy of Sciences, ul. Favorskogo 1,
Irkutsk, 664033 Russia
Irkutsk State Technical University, ul. Lermontova 83,
Irkutsk, 664074 Russia
denser with a calcium chloride tube. The mixture was
heated with stirring for 30 min at 130°C until the reac-
tion began (the appearance of a yellow color); then the
heating was turned off. After the reaction completed,
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