Sulfuric Acid → Ibuprofen, (+-)-

Participants

Reaction Steps

A 5.11 g. portion of the crude ibuprofen methyl ester prepared as described above was dissolved in 20 ml. of hexane and 12 ml. of methanol and cooled to 0° to 5° C. Then 6.0 g. (75 mmole) of a 50% sodium hydroxide solution was added and the resulting mixture was heated under reflux for 2 hours. On cooling, the mixture was transferred to a separatory funnel with about 50 ml. of 1 N sodium hydroxide solution and hexane. The hexane layer was extracted with about 10 ml. of 1 N aqueous sodium hydroxide and the combined aqueous layer was extracted with 50 ml. of fresh hexane. The neutral fraction isolated from the combined hexane extracts consisted primarily of p-isobutylpropiophenone. The aqueous layer was acidified with 50% aqueous sulfuric acid and extracted 3 times with 50 ml. portions of hexane. The combined hexane extracts were washed 3 times with 50 ml. portions of water and dried over sodium sulfate. Removal of solvent by vacuum evaporation gave crude ibuprofen as a pale yellow solid, weighing 4.20 g., having a purity of 96.7% by Glc analysis, again the impurities being about 1.4% p-isobutylbenzoic acid and 1.1% of the meta isomer of ibuprofen. The crude yield was 80.8% of theory. Recrystallization of the crude ibuprofen from hexane (2 ml./g.) gave 3.44 g. (70.3% chemical yield) ibuprofen.

Provenance & Evidence