Patent ID: 7285678
Filing Date: 2007-10-23
Classification: C07C

Abstract:
1. A method for removing impurities from 2-nitro-4-methylsulfonylbenzoic acid which comprises the following steps, (a) dissolving 2-nitro-4-methylsulfonylbenzoic acid in water at a pH of about 2 to 10, followed by filtration; (b) contacting an aqueous solution of 2-nitro-4-methylsulfonylbenzoic acid with activated carbon at a pH of about 2 to 10; (c) treating an aqueous solution of 2-nitro-4-methylsulfonylbenzoic acid with sufficient base to hydrolyze undesired nitro and dinitro substituted impurities; followed by maintaining the resulting aqueous solution comprising 2-nitro-4-methylsulfonylbenzoic acid at a temperature of up to about 95° C., and adjusting the pH of said solution to about a pH which is sufficient to effect crystallization of 2-nitro-4-methylsulfonylbenzoic acid upon cooling; wherein in said method, the method steps (a) and (b) are utilized, in any order; or wherein steps (b) and (c) are utilized, in any order; or wherein steps (a), (b) and (c) are utilized, in any order; or wherein steps (a), (b) and (c) are utilized in order.