[CH3:1][O:2][C:3]1[CH:11]=[C:10]([O:12][CH3:13])[CH:9]=[CH:8][C:4]=1[C:5]([OH:7])=[O:6].[N+:14]([O-])([OH:16])=[O:15]>S(=O)(=O)(O)O>[CH3:1][O:2][C:3]1[CH:11]=[C:10]([O:12][CH3:13])[C:9]([N+:14]([O-:16])=[O:15])=[CH:8][C:4]=1[C:5]([OH:7])=[O:6](Alternative method) A 2.00 g portion of 2,4-dimethoxybenzoic acid was dissolved in 30 ml of sulfuric acid, and 0.49 ml of concentrated nitric acid was added under ice-cooling. After 3 hours of stirring at room temperature, this was poured into 100 g of ice water, and the thus formed crystals were collected by filtration, washed with water-methanol and then dried under a reduced pressure to give 1.41 g of 2,4-dimethoxy-5-nitrobenzoic acid. The physicochemical properties were identical to those of the compound obtained by the former method.
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