Benzoylformic Acid from Styrene
Charles D. Hurd, R. W. McNamee, Frank O. Green
J. Am. Chem. Soc. 61, 2979-2980 (1939)
Ph-CH2=CH2 + KMnO4 -> Ph-CO-COOH
Experimental
Eighteen grams (0.173 mole) of styrene and 9 g. (0.225 mole) of sodium hydroxide were shaken with 100 cc. of water in a 2-liter flask fitted with an air condenser. To this mixture was added in six portions a hot (70°C) solution of 75 g. (0.474 mole) of potassium permanganate in 1500 cc. of water. After each addition the mixture was shaken vigorously for two minutes and cooled under the water tap so that the reaction temperature was kept at about 70°C. When all the permanganate had been introduced, the excess was reduced with about 100 cc. of alcohol and the manganese dioxide filtered off and washed with water. The filtrate and washings were combined and evaporated down to 400 cc., then acidified with concentrated hydrochloric acid. The 1.5 g. of benzoic acid which separated was removed by filtration. When the addition of hydrochloric acid failed to precipitate any more benzoic acid the solution was extracted several times with ether. On evaporation of the ether, 20.4 g. of a light yellow liquid remained. This crude benzoylformic acid contained 2 to 3 cc. of water which made it quite insoluble in carbon disulfide. The water was removed by distilling with 7 cc. of toluene, An alternative procedure for removing the water was to dry the ether solution with calcium chloride. The residual acid, 18 g. (0.120 mole) or 69% yield, was dissolved in 30 cc. of carbon disulfide and the solution cooled with ice and salt. About 10 g. of crystals came down in the first crop and 5-6 g. in subsequent crops. Recrystallization gave 14.5 g. (0.096 mole) or 55% yield, of benzoylformic acid which melted at 59-61°C.
