3-Nitrophthalic acid

Pale yellow crystals. soluble in hot water, methanol, ethanol, slightly soluble in ether, insoluble in chloroform, carbon tetrachloride, carbon disulfide, benzene.

3-Nitrophthalic Acid is a useful chemical in organic synthesis. It is also an impurity of Apremilast.

3-Nitrophthalic acid may be used as starting reagent in the synthesis of modified 2-iodoxybenzoic acid derivatives. It may be used in the synthesis of brucinium 2-carboxy-6-nitrophthalate dihydrate (systematic name: 2,3-dimethoxy-10-oxostrychnidinium 2-carboxy-6-nitrophthalate dihydrate), via heating with brucine.

Phthalic anhydride was added to concentrated sulfuric acid, stirring under the passage of water vapor heating to 80 °C, fuming nitric acid was added dropwise, the reaction temperature to maintain 100-110°C, add the end of the heat above 110°C for 2h, placed in the overnight pour into the water, and filtered. The filter cake was recrystallized with water to obtain 3-Nitrophthalic acid. Yield of about 30%.

The Journal of Organic Chemistry, 39, p. 2468, 1974 DOI: 10.1021/jo00930a051

3-Nitrophthalic acid is a degradation product of isoxaben herbicide. It acts as ligand and forms rare-earth complexes.

A preparative hazard. When heated to decomposition it emits toxic fumes of NOx.

Crystallise 3-nitrophthalic acid from hot water (1.5mL/g). Dry it in air. The amide has m 201o (from EtOH). [Beilstein 9 H 823, 9 IV 3275.]