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 1N sodium hydroxide solution and hexane. The hexane layer was extracted with about 10 ml. of 1N 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