Org. Synth. 1954, 34, 42
DOI: 10.15227/orgsyn.034.0042
DIPHENYLACETYLENE
[Acetylene, diphenyl-]
Submitted by Arthur C. Cope, Douglas S. Smith, and Robert J. Cotter
1.
Checked by Charles C. Price and Thomas F. McKeon, Jr..
1. Procedure
A solution of 105.1 g. (0.5 mole) of benzil (Note 1) in 325 ml. of n-propyl alcohol is prepared in a 1-l. round-bottomed flask which is fitted with an efficient reflux condenser. To this solution 76 g. (1.30 moles) of 85% hydrazine hydrate (Note 2) is added, and the mixture (Note 2) is heated under reflux for 60 hours. The solution is cooled with an ice bath, and the benzil dihydrazone is separated by suction filtration. The crystals are washed with 200 ml. of cold, absolute ethanol and dried (Note 3) on the suction filter for 1 hour. The yield of benzil dihydrazone is 99–106 g. (83–89%), m.p. 150–151.5°.
The benzil dihydrazone is added to 480 ml. of reagent grade benzene in a 1-l. three-necked flask fitted with a reflux condenser and a sealed stirrer. A small amount of yellow mercuric oxide (2–4 g.) is added to the mixture with stirring to keep the benzil dihydrazone suspended, and the mixture is warmed slightly on a steam bath. Nitrogen is evolved, and the mixture turns gray. Additional yellow mercuric oxide is then introduced in small portions so as to keep the reaction mixture gently refluxing until a total of 240 g. (1.11 moles) has been added. The mixture is stirred for 1 hour and allowed to stand overnight. It is then filtered, and the residue (mercury and mercuric oxide) is washed with 100 ml. of benzene, which is combined with the original red benzene is filtrate. After drying over anhydrous sodium sulfate, the benzene is removed by distillation under reduced pressure by heating with a water bath. The residue is distilled from a flask connected to a short distillation head at 95–105°/0.2–0.3 mm. and yields 60–65 g. (67–73% from benzil) of diphenylacetylene, m.p. 59–60°. The product can be recrystallized from 100 ml. of 95% ethanol, m.p. 60–61° (Note 4).
2. Notes
1.
Eastman Kodak Company white label grade benzil or material prepared by the procedure described in
Organic Syntheses2 is satisfactory.
2.
Hydrazine hydrate (85%) as supplied by the Edwal Laboratories was used. On addition of this reagent to the
benzil solution, the
monohydrazone of benzil precipitates, but it redissolves readily on heating.
3.
Benzil dihydrazone should not be dried in a
vacuum desiccator, for it sublimes easily.
4.
Diphenylacetylene prepared by this method has the advantage of being uncontaminated with
stilbene, with which it forms a solid solution not readily separable.
3 Di-p-tolylacetylene4 and
α-naphthylphenlacetylene5 have been prepared by the same method in high yields.
3. Discussion
In addition to the methods mentioned in a previous preparation,
6 diphenylacetylene has been prepared by the action of
potassium hydroxide on
5,5-diphenyl-3-nitroso-2-oxazolidone (
100%),
7 on
meso-stilbene dibromide in triethylene glycol,
8 and on
stilbene tetrabromide in butyl alcohol;
9 by the condensation of
bromobenzene with
sodium phenylacetylide in liquid ammonia,
10 by the oxidation of
benzil dihydrazone with
silver trifluorocetate in triethylamine,
11 and by the pyrolysis of
α-benzoylbenzylidenetriphenylphosphorane.
12 The present procedure is a modification of that of Schlenk and Bergmann.
13This preparation is referenced from:
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
monohydrazone of benzil
α-naphthylphenlacetylene
ethanol (64-17-5)
ammonia (7664-41-7)
Benzene (71-43-2)
sodium sulfate (7757-82-6)
nitrogen (7727-37-9)
mercury (7439-97-6)
mercuric oxide (21908-53-2)
butyl alcohol (71-36-3)
Benzil (134-81-6)
potassium hydroxide (1310-58-3)
bromobenzene (108-86-1)
n-propyl alcohol (71-23-8)
hydrazine hydrate (7803-57-8)
sodium phenylacetylide
stilbene
Diphenylacetylene,
Acetylene, diphenyl- (501-65-5)
triethylamine (121-44-8)
Benzil dihydrazone (4702-78-7)
5,5-diphenyl-3-nitroso-2-oxazolidone
triethylene glycol (112-27-6)
stilbene tetrabromide
silver trifluorocetate
α-benzoylbenzylidenetriphenylphosphorane
Di-p-tolylacetylene
meso-stilbene dibromide
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