In a
2-l. three-necked flask, fitted with a
separatory funnel, a
reflux condenser, and a
mercury-sealed stirrer,
27 g. (1.1 gram atoms) of magnesium,
181 g. (122 ml., 1.15 moles) of bromobenzene, and a total of
450 ml. of anhydrous ether (Note
1) are converted into
phenylmagnesium bromide by the procedure described in
Org. Syntheses Coll. Vol. 1, 226 (1941).
Calcium chloride tubes are used to prevent the entrance of moisture through the condenser and the
separatory funnel during the addition. In order to dissolve all the
magnesium it may be necessary, in some instances, to continue stirring for longer than the prescribed 10 minutes after addition is complete.
To the Grignard solution,
75 g. (71.5 ml., 0.5 mole) of ethyl benzoate in
200 ml. of dry benzene (Note
2) is added at such a rate that the mixture refluxes gently. The flask is cooled in a pan of cold water during the addition, which requires about an hour. After the addition is complete, the mixture is refluxed for an hour on a
steam bath. The reaction mixture is cooled in cooled an
ice-salt bath and then poured slowly, with constant stirring, into a mixture of 1.5 kg. of cracked ice and
50 ml. of concentrated sulfuric acid. The mixture is stirred at intervals until all the solid that separates at the benzene-water interface has dissolved. If necessary,
50 g. of ammonium chloride is added to facilitate the decomposition of the magnesium salt, and additional
benzene may be added if the amount present is insufficient to dissolve all the product. When the solids have disappeared, the
benzene layer is separated and washed, successively, with 200 ml. of water,
200 ml. of a 5% solution of sodium bicarbonate, and finally with 200 ml. of water. The solvents are removed as completely as possible by distillation on a steam bath, and the remaining solution or solid mass is steam-distilled to remove
biphenyl and unchanged
bromobenzene. The product is filtered, washed with water, and dried. The crude
triphenylcarbinol, which weighs
120–125 g., is recrystallized from
carbon tetrachloride (4 ml. of solvent per gram of solid). The weight of the first crop of colorless
triphenylcarbinol is
110–115 g. (Note
3). A second crop may be obtained by heating the filtrate with a gram of
Norit, then concentrating to about 125 ml. and cooling the solution. The total yield of
triphenylcarbinol melting at
161–162° is
116–121 g. (
89–93%) (Note
4).