Sulfuric Acid → Dibenzoylmethane

Participants

Reaction Steps

1-Methoxy-2-propanol (923 g; 10.24 mol), sodium hydroxide (256 g; 6.4 mol), and xylenes (1820 g; 2.12 L) were placed into a four-necked, round bottom, five 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 106-116° C.). When no more water was collected (280 mL of lower phase), some solvent was distilled off (1,200 mL), while xylenes (432.2 g, dry) were replaced, until no more alcohol was detected in the distillate. The mixture in the flask was cooled down to and kept at 95° C., and the fractionation column and trap were replaced with a reflux condenser, while maintaining the nitrogen stream. Methyl benzoate (1089 g; 8.0 mol) was added and slow addition (over a period of 38 minutes) of acetophenone (481 g; 4.0 mol) by means of a peristaltic pump was begun. After 75 minutes from the beginning of the addition of the ketone, the mixture was cooled down (an ice bath was used), and then acidified by the slow addition of 98% sulfuric acid (392 g) with stirring. Sodium bicarbonate (185 g) was added for neutralizing the mixture. The slurry was distilled under vacuum (18 cm Hg, Tpot=84° C.), and at the same time 1,400 g of xylenes was added. The distillate (2,094 g) contains methoxypropanol, which can be recovered (see below).

Provenance & Evidence