Sulfuric Acid → 4-(Methylamino)-3-nitrobenzoic acid

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Reaction Steps

400 g (1.98 mol) of 4-chloro-3-nitrobenzoic acid were suspended in 1025 g of a 25-30% aqueous solution of methylamine. After heating to reflux temperature, an orange solution was obtained. The solution was kept at reflux temperature for 4 hours. The solution was cooled to room temperature, and pH was adjusted to about 2 by addition of 2M aqueous sulphuric acid. Precipitation of an orange solid was observed, which was isolated by filtration. The filtered cake was washed with 500 mL of water. The wet solid was mixed with 1.5 L of ethanol and heated to reflux temperature for 1 hour. After cooling to room temperature, the resulting suspension was filtered and the cake was dried at 60° C. under vacuum to obtain 371 g of 4-(methylamino)-3-nitrobenzoic acid as an orange powder. Yield: 95.5%. Purity (HPLC, method 2): 99.4%.

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