Purification of 2-nitro-4-methylsulphonylbenzoic acid

Details Purification of 2-nitro-4-methylsulphonylbenzoic acid Purification of 2-nitro-4-methylsulphonylbenzoic acid

2007-10-23

2007-10-23

Richter, Johann R. (Department: 1621)

Organic compounds -- part of the class 532-570 series

Organic compounds

Carboxylic acids and salts thereof

C504S348000

Reexamination Certificate

active

10472962

ABSTRACT:
A method for removing impurities from 2-nitro-4-methylsulfonylbenzoic acid which comprises at least two of the following steps, in any order, (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-methylsulfonylbenizoic 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.

REFERENCES:
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patent: 5424481 (1995-06-01), Hagen
patent: 6218579 (2001-04-01), Jones et al.
patent: 90 06301 (1990-06-01), None

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