Organic Syntheses, CV 2, 606
Submitted by Homer Adkins and Walter Zartman.
Checked by C. R. Noller and F. M. McMillan.
1. Procedure
In a
3-l. three-necked flask, fitted with a
mechanical stirrer, a
reflux condenser, and a
separatory funnel, are placed
24.3 g. (1 gram atom) of magnesium turnings,
500 cc. of absolute ether, a crystal of
iodine, and a
5- to 10-cc. portion of 126.5 g. (115 cc., 1 mole) of freshly distilled benzyl chloride (b.p.
177–179°). In a few minutes the reaction starts (Note
1) and is controlled if necessary by cooling with a wet towel. The stirrer is started, and the balance of the
benzyl chloride is run in as fast as the refluxing will permit. The addition requires from one to two hours, and when completed the mixture is refluxed on the
steam bath with stirring for three hours. With the stirrer still running,
182 g. (1 mole) of benzophenone (Org. Syn. Coll. Vol. I, 1941, 95) dissolved in
500 cc. of absolute ether is added at such a rate that the mixture refluxes rapidly. This requires about twenty minutes, and then the reaction mixture is allowed to stand for two hours (Note
2).
The flask is placed in an
ice bath, 700 g. of cracked ice is added, and the
magnesium hydroxide is dissolved by adding
500 cc. of cold 20 per cent sulfuric acid. The
ether layer is separated, and the water layer extracted with two
200-cc. portions of ether. The
ether is distilled from the combined extracts, and the residual liquid is refluxed for two hours with
100 cc. of 20 per cent sulfuric acid to dehydrate the carbinol. The layers are separated and the product vacuum-distilled (Note
3). The fraction boiling at
215–225°/15 mm. weighs
160–170 g. and melts at
60–68° (Note
4). Crystallization from
900 cc. of hot 95 per cent alcohol and cooling to 0° gives
140–150 g. of the hydrocarbon melting at
68–69° (
54–59 per cent of the theoretical amount). Concentration of the mother liquor to 150 cc. and cooling gives
5–10 g., m.p.
65–67.5° (Note
5).
2. Notes
1. If the reaction does not start within thirty minutes, the mixture is warmed on a
water bath with the stirrer running.
2. Slightly better yields are obtained if the reaction mixture is allowed to stand overnight.
3. The product should not be washed with water as the presence of a trace of
sulfuric acid during the distillation seems to be necessary to complete the dehydration.
4. Seeding is usually necessary to induce crystallization.
3. Discussion
This preparation is referenced from:
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