A Publication
of Reliable Methods
for the Preparation
of Organic Compounds
Annual Volume
Org. Synth. 1944, 24, 53
DOI: 10.15227/orgsyn.024.0053
[Methane, diazodiphenyl-]
Submitted by Lee Irvin Smith and Kenneth L. Howard.
Checked by H. R. Snyder, R. L. Rowland, and H. J. Sampson, Jr..
1. Procedure
In a pressure bottle are placed 19.6 g. (0.1 mole) of benzophenone hydrazone (Note 1), 22 g. (0.1 mole) of yellow oxide of mercury, and 100 ml. of petroleum ether (b.p. 30–60°). The bottle is closed, wrapped in a wet towel, and shaken mechanically at room temperature for 6 hours. The mixture is then filtered to remove mercury and any benzophenone azine (Note 2), and the filtrate is evaporated to dryness under reduced pressure at room temperature. The crystalline residue of diphenyldiazomethane melts when its temperature reaches that of the room (Note 3), but it is difficult to purify and this product is pure enough for all practical purposes. The material weighs 17.3–18.6 g. (89–96%). The product should be used immediately (Note 4).
2. Notes
1. Benzophenone hydrazone is most readily prepared from benzophenone (40 g., 0.22 mole) in 150 ml. of absolute ethanol with 41.2 g. (0.824 mole) of 100% hydrazine; the mixture is heated under reflux for 10 hours. On cooling in ice, colorless benzophenone hydrazone separates. The yield is 37.5 g. (87%), m.p. 97–98°. If anhydrous hydrazine is not available, it may be prepared by the method described in Org. Syntheses, 24, 53 (1944).
2. This ketazine is insoluble in petroleum ether.
3. The reported melting point of diphenyldiazomethane is 29–30°, but this melting point is shown only after the substance has been recrystallized from petroleum ether.
4. On standing, diphenyldiazomethane decomposes to yield benzophenone azine. In one of the checkers' runs the product was stored at room temperature; after 2 days, crystals of the azine were visible. The product at this stage was assayed by treatment with benzoic acid; addition of 6.8 g. of the diazo compound in a thin stream to a solution of 17 g. of benzoic acid in 90 ml. of ether, and, after 30 minutes, extraction of the excess benzoic acid with dilute sodium hydroxide followed by distillation of the ether gave 7.4 g. (75%) of crude benzohydryl benzoate melting at 83–85°. In the same procedure the freshly prepared diazo compound gave a quantitative yield of the crude ester.
3. Discussion
Diphenyldiazomethane has been prepared only by oxidation of benzophenone hydrazone.1 The procedure given above is that of Staudinger, Anthes, and Pfenninger, with minor changes.
This preparation is referenced from:

References and Notes
  1. Staudinger, Anthes, and Pfenninger, Ber., 49, 1932 (1916)

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

petroleum ether

oxide of mercury

benzohydryl benzoate

ethanol (64-17-5)

ether (60-29-7)

sodium hydroxide (1310-73-2)

Benzoic acid (65-85-0)

mercury (7439-97-6)

Benzophenone (119-61-9)

hydrazine (302-01-2)

Diphenyldiazomethane (883-40-9)

Methane, diazodiphenyl-

benzophenone hydrazone (5350-57-2)

benzophenone azine (983-79-9)