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Org. Synth. 1937, 17, 89
DOI: 10.15227/orgsyn.017.0089
TRIPHENYLETHYLENE
[Ethylene, triphenyl-]
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.
5. By the same procedure, stilbene may be prepared from benzaldehyde and benzylmagnesium chloride in 25–35 per cent yield.
3. Discussion
Triphenylethylene has been prepared by the reaction between phenylmagnesium bromide and desoxybenzoin or ethyl phenylacetate;1 and by the reaction between diphenylketene-quinoline and benzaldehyde.2 The procedure given above is an adaptation of that published by Hell and Wiegandt.3 The intermediate diphenylbenzylcarbinol can be dehydrated very effectively by heating with potassium bisulfate or by boiling its solution in glacial acetic acid.4
This preparation is referenced from:

References and Notes
  1. Klages and Heilmann, Ber. 37, 1455 (1904).
  2. Staudinger and Kon, Ann. 384, 89 (1911).
  3. Hell and Wiegandt, Ber. 37, 1429 (1904).
  4. Van de Kamp and Sletzinger, J. Am. Chem. Soc. 63, 1880 (1941).

Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)

Desoxybenzoin

diphenylketene-quinoline

alcohol (64-17-5)

sulfuric acid (7664-93-9)

acetic acid (64-19-7)

ether (60-29-7)

magnesium turnings (7439-95-4)

potassium bisulfate (7646-93-7)

benzaldehyde (100-52-7)

iodine (7553-56-2)

Benzophenone (119-61-9)

benzyl chloride (100-44-7)

benzylmagnesium chloride (6921-34-2)

magnesium hydroxide

Phenylmagnesium bromide (100-58-3)

Ethyl phenylacetate (101-97-3)

Triphenylethylene,
Ethylene, triphenyl- (58-72-0)

stilbene

diphenylbenzylcarbinol (4428-13-1)