A Publication
of Reliable Methods
for the Preparation
of Organic Compounds
Annual Volume
Org. Synth. 1935, 15, 62
DOI: 10.15227/orgsyn.015.0062
[Acetophenone, α-diazo-α-phenyl-]
Submitted by Costin D. Nenitzescu and Eugen Solomonica.
Checked by Louis F. Fieser and Ralph S. Temple.
1. Procedure
Thirty grams (0.134 mole) of benzil hydrazone (Note 1) is mixed in a mortar with 60 g. (0.28 mole) of yellow mercuric oxide and 15 g. of anhydrous sodium sulfate (Note 2). The mixture is introduced into a 500-cc. glass-stoppered bottle and covered with 200 cc. of absolute ether (Note 3). Four cubic centimeters of a cold, saturated solution of alcoholic potassium hydroxide is added to catalyze the reaction (Note 4), and the mixture is shaken for ten to fifteen minutes. The solution is filtered by gravity through a fine paper, and the residue is washed several times with ether until the liquid is only slightly colored. The combined ethereal extracts are evaporated to dryness at the pressure of the water pump by heating the flask in a water bath to a temperature not greater than 40° (Note 5). The yellow, crystalline material is dried on a porous plate and recrystallized from anhydrous ether. The yield of azibenzil which melts at about 79° with decomposition is 26–28 g. (87–94 per cent of the theoretical amount) (Note 6).
2. Notes
1. Benzil hydrazone1 may be prepared as follows:2 A mixture of 52 g. (0.4 mole) of hydrazine sulfate (Org. Syn. Coll. Vol. I, 1941, 309), 110 g. (0.8 mole) of sodium acetate, and 250 g. of water is boiled five minutes, cooled to about 50°, and 225 cc. of methyl alcohol added. The precipitated sodium sulfate is filtered and washed with a little alcohol.
A hot solution of 50 g. (0.24 mole) of benzil (Org. Syn. Coll. Vol. I, 1941, 87) in 75 cc. of methyl alcohol is prepared, and the above solution, heated to 60°, is added. Most of the benzil hydrazone separates immediately, but the yield is increased by refluxing for half an hour. The hydrazone is filtered from the cold solution and washed with a little ether to remove the yellow color. The yield is 50.5 g. (94 per cent of the theoretical amount), melting at 147–151° with decomposition.
Directions for preparing benzil hydrazone from benzil and hydrazine hydrate are given in Org. Syn. 20, 48.
2. The sodium sulfate absorbs the water formed during the reaction.
3. By using ether, instead of benzene or petroleum ether as specified in the older methods, the evaporation of the solvent after the reaction is facilitated.
4. Without this catalyst the oxidation may require several hours and the results may vary considerably, depending largely upon the quality of the mercuric oxide.
5. The material may explode if the evaporation is carried out at atmospheric pressure on the steam bath.
6. This procedure may be used also for the preparation of diazofluorene.3
3. Discussion
Phenylbenzoyldiazomethane, azibenzil, has been prepared by the oxidation of benzil hydrazone with mercuric oxide,4 using benzene or petroleum ether as the solvent, and without the catalyst here specified.

References and Notes
  1. Curtius and Thun, J. prakt. Chem. (2) 44, 176 (1891).
  2. Private communication from C. F. H. Allen.
  3. Staudinger and Kupfer, Ber. 44, 2207 (1911); Staudinger and Gaule, ibid. 49, 1955 (1916).
  4. Curtius and Thun, J. prakt. Chem. (2) 44, 182 (1891).

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

petroleum ether


Benzene (71-43-2)

methyl alcohol (67-56-1)

ether (60-29-7)

sodium acetate (127-09-3)

sodium sulfate (7757-82-6)

mercuric oxide (21908-53-2)

Benzil (134-81-6)

potassium hydroxide (1310-58-3)

hydrazine hydrate (7803-57-8)

Hydrazine sulfate (10034-93-2)

Acetophenone, α-diazo-α-phenyl- (3469-17-8)

Benzil hydrazone (5344-88-7)