Org. Synth. 1926, 6, 32
Submitted by C. F. H. Allen and S. Converse.
Checked by Henry Gilman and N. J. Beaber.
In a 2-l. three-necked flask, fitted with a separatory funnel, reflux condenser, and stirrer, is placed 27 g. (1.1 atoms) of magnesium turnings. A mixture of 30 g. of bromobenzene and 70 cc. of dry ether is run in and the flask warmed gently until the reaction becomes rapid. Stirring is then started, and the vessel is surrounded by a dish of cold water. A mixture of 151 g. of bromobenzene (total: 181 g., 1.15 moles) and 380 cc. of dry ether is run in at such a rate as to cause vigorous refluxing; when the addition is complete (one hour) the whole is stirred for ten minutes.
After the flask has been cooled by immersion in ice water, 44 g. (0.5 mole) of dry ethyl acetate (Note 1) in an equal volume of ether is added over a period of twelve minutes. The cooling bath is removed and stirring is continued for ten minutes. When the reaction flask has again been cooled by the ice-water bath, a previously prepared ammonium chloride solution (Note 2) is added, very slowly at first, over a period of ten minutes, during which a pasty solid separates.
The ether layer is decanted into a separatory funnel, and to it is added a 50-cc. ether extract of the pasty residue. The ether is removed by dropping the solution into a 500-cc. round-bottomed flask attached to a condenser and immersed in an oil bath heated to 210–215°. The flask is removed from the oil bath, cooled, and disconnected from the condenser; 100 cc. of 20 per cent sulfuric acid is added. The flask is fitted with a reflux condenser, and the contents are boiled for one hour. The aqueous layer is now removed, and the residual oil, without being washed, is distilled at a pressure of about 30 mm. and a bath temperature of about 210° (Note 3). At first a low-boiling fraction consisting of bromobenzene (12–14 g.) and traces of water distils, after which the diphenylethylene comes over as a colorless liquid, the last portions being slightly yellowish. The brownish residue contains polymerization and decomposition products. On redistillation, the pure hydrocarbon boils at 113°/2 mm. (Note 4). The yield is 60–66 g. (67–70 per cent of the theoretical amount based on ethyl acetate) (Note 5).
The grade of ethyl acetate
is very important. If ordinary ethyl acetate
is used it may be purified by washing with twice its volume of water, drying over fused potassium carbonate
, refluxing with phosphorus pentoxide
, filtering, and fractionating, whereupon practically all comes over at constant temperature. The addition to the Grignard reagent should be cautious at first, to avoid a vigorous reaction that frequently occurs after about 15 cc. has been added.
The ammonium chloride solution is prepared by dissolving 50 g.> of ammonium chloride
in 150 cc. of water at 25–30°. The literature recommends 30 per cent sulfuric acid
for decomposing the magnesium compound
; when this is used, the yield drops to 50–55
per cent, probably owing to the ready polymerization of the hydrocarbon in the presence of mineral acids.
This treatment obviates the necessity of isolating the intermediate carbinol
. The carbinol, if desired, can be obtained in yields up to 75
per cent from the combined, dried, ether
The hydrocarbon is reported to boil at 123–5°/5 mm.
; 134°/10 mm.1
; 139°/11 mm.2
; 156°/25 mm.3
; 164°/34 mm.3
; and at 277°/760 mm.4
The yield is decreased by about 10
per cent if only an equivalent molecular quantity of phenylmagnesium bromide
can be prepared by the action of alcoholic potassium hydroxide
on unsymmetrical diphenylchloroethane
by the action of aluminum chloride
and by dehydration of the carbinol which can be prepared by the action of methylmagnesium iodide
or phenylmagnesium bromide
or ethyl acetate
The procedure described is adapted from that of Stadnikov.8
This preparation is referenced from:
Chemical Abstracts Nomenclature (Collective Index Number);
potassium carbonate (584-08-7)
sulfuric acid (7664-93-9)
ethyl acetate (141-78-6)
ammonium chloride (12125-02-9)
magnesium turnings (7439-95-4)
aluminum chloride (3495-54-3)
potassium hydroxide (1310-58-3)
Phenylmagnesium bromide (100-58-3)
methylmagnesium iodide (917-64-6)
phosphorus pentoxide (1314-56-3)
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