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Org. Synth. 1944, 24, 16
DOI: 10.15227/orgsyn.024.0016
BENZOYLFORMIC ACID
[Glyoxylic acid, phenyl-]
Submitted by T. S. Oakwood and C. A. Weisgerber.
Checked by R. L. Shriner and Charles R. Russell.
1. Procedure
In a 1-l. flask are placed 50 g. (0.38 mole) of benzoyl cyanide (p. 112) and 500 ml. of concentrated hydrochloric acid (sp. gr. 1.18). The mixture is shaken occasionally until the solid is dissolved completely and is then allowed to stand at room temperature for 5 days (Note 1). At the end of this time the clear yellow solution is poured into 2 l. of water and extracted with one 400-ml. portion and three 250-ml. portions of ether. The ether is removed by distillation from a steam bath, and the residual oil is placed in a vacuum desiccator containing phosphorus pentoxide and solid sodium hydroxide and allowed to remain there until dry (Note 2). The yield of crude solid acid melting from 57° to 64° is about 55–56 g. (96–98%). The crude acid is dissolved in 750 ml. of hot carbon tetrachloride, and 2 g. of Norit is added (Note 3). The solution is filtered and allowed to cool to room temperature and then cooled in an ice-water mixture until crystallization is complete. The solid acid is filtered with suction, and the solvent remaining on the crystals is removed by placing the product in a vacuum desiccator for about 2 days. The yield of slightly yellow benzoylformic acid melting at 64–66° is 42–44 g. (73–77%) (Note 4).
2. Notes
1. With occasional shaking about a day is necessary for complete solution of the solid benzoyl cyanide. A yellow oil separates which dissolves on shaking. At the end of this time some ammonium chloride occasionally separates.
2. If the oil does not crystallize it is cooled in an ice-water mixture until solidification is complete. The solid is returned to the desiccator for complete drying. The desiccator must be evacuated slowly or spattering will take place.
3. If decolorizing carbon is not used, the acid tends to separate as an oil which solidifies on cooling.
4. Titration with standard sodium hydroxide solution showed the acid to be about 99% pure.
3. Discussion
Benzoylformic acid can be prepared by the oxidation of acetophenone with potassium permanganate in alkaline solution,1 by the oxidation of mandelic acid with potassium permanganate in alkaline solution,2,3 and by the hydrolysis of benzoyl cyanide with concentrated hydrochloric acid.4

References and Notes
  1. Claus and Neukranz, J. prakt. Chem. (2) 44, 80 (1891).
  2. Acree, Am. Chem. J., 50, 391 (1913).
  3. Org. Syntheses Coll. Vol. 1, 241 (1941).
  4. Boeseken and Felix, Rec. trav. chim., 40, 569 (1921).

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

hydrochloric acid (7647-01-0)

ether (60-29-7)

ammonium chloride (12125-02-9)

sodium hydroxide (1310-73-2)

Mandelic acid (90-64-2)

potassium permanganate (7722-64-7)

carbon tetrachloride (56-23-5)

Acetophenone (98-86-2)

decolorizing carbon,
Norit (7782-42-5)

Benzoylformic acid,
Glyoxylic acid, phenyl- (611-73-4)

Benzoyl cyanide (613-90-1)

phosphorus pentoxide (1314-56-3)