Sulfuric Acid → 2-Acetoxy-3,5-dichlorobenzoic acid

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Reaction Conditions

Reaction Steps

A 1 L, round-bottom, three neck flask equipped with: a mechanical stirrer, a thermometer and a 125 mL dropping funnel with pressure equilibration was placed in a water bath maintained at 65° C. The following reagents were subsequently charged to the flask with an efficient stirring: 250 mL of dry toluene, 2.5 mL of concentrated sulfuric acid and 207 g of well ground, solid 3,5-dichlorosalicylic acid, which forms a mobile suspension. When the temperature of this constantly stirred mixture reached 60° C. (with the water bath temperature maintained at 65° C.) a drop-wise addition of 108 g (100 mL) of acetic anhydride was initiated and completed within 30 min. During the acetic anhydride addition the temperature of the reaction mixture was not allowed to exceed 75° C. After completing the addition, the mixture was stirred and heated to 70° C. for another 4 h. After this time, the agitation was stopped and the mixture cooled over night to room temperature. The white crystals that separated from the mixture were filtered off, washed with 2×10 mL of ice-cold toluene and vacuum dried at 50° C. to yield 206 g (82.7% yield) of 2-acetoxy-3,5-dichlorobenzoic acid. An additional 30.6 g (12.3%% yield) of the product was recovered by: concentrating the filtrate to ½ of the original volume, cooling the solution in an ice-water bath, filtering off the crystalline product and vacuum drying it at 50° C.

Provenance & Evidence