Sulfuric Acid → Dibenzoylmethane

Participants

Reaction Steps

Benzhydrol (189.77 g; 1.03 mol), potassium hydroxide (84.3%; 66.56 g; 1.0 mol) and cumene (375 mL) were placed into a four-necked, round bottom, one liter flask equipped with a stirrer, a thermometer, and an Oldershaw column with a Dean-Stark trap and a condenser. The mixture was heated to boiling with stirring under a blanket of nitrogen and the water was azeotroped out (temperature of reflux 148-150° C). When no more water was collected (27 mL, yield=95%, about 2 hours) the mixture was cooled down to and kept at 90° C. The fractionation column and trap were replaced with a reflux condenser, while maintaining the nitrogen stream. Methyl benzoate (181.5 g; 1.33 mol) was added at once, and slow addition (12 minutes) of acetophenone (80.10 g; 0.667 mol) by means of a syringe pump was begun. After 60 minutes from the beginning of the addition of the ketone, the mixture was allowed to cool to room temperature, whereupon it was acidified with 10% sulfuric acid. The cumene layer was washed with a saturated solution of sodium bicarbonate in water and then with water. The organic layer was then concentrated under vacuum in a rotary evaporator. The residue was crystallized from 90% isopropanol, affording DBM (112.13 g, 75% yield) having a purity of 98% (GC).

Provenance & Evidence