Sulfuric Acid → 5-Hydroxy-2-iodobenzoic acid

Participants

Reaction Steps

Suspension of 2-amino-5-hydroxybenzoic acid (5.0 g, 32.7 mmol) in deionized water (100 mL) was mixed with 60 mL of concentrated sulfuric acid, which was added dropwise, resulting in a clear solution, which was held at 4° C. overnight, yielding suspension of white crystals. The suspension, while still cold, was mixed with 20 mL of an aqueous solution of sodium nitrite (2.4 g, 34.8 mmol). The resulting yellow-orange solution was mixed with 20 mL of an aqueous solution of potassium iodide (7.4 g, 44.6 mmol), which was added dropwise. The resulting mixture, dark-brown in color, was kept at 90° C. for 1 h and then was kept at 4° C. overnight affording dark red to brown crystals, which were filtered off and redissolved in 100 mL of deionized boiling water. Activated charcoal (7 g) was added to the hot solution, which was held at 90° C. for 1 h. The slurry, while hot, was filtered off using filter paper (retention, 10 μm) and the supernatant was kept at 4° C. resulting in faintly orange crystals, which were filtered off and dried in a desiccator at r.t. C7H5IO3, found (calc): C, 31.51 (31.84); H, 2.14 (1.91); I, 47.31 (48.07). 1H NMR (400 MHz, DMSO-d6): δ 5.1 (s, 1H, OH), 6.81, 7.38, 7.71 (H3, H5, H2, 1H each, in aromatic ring), 11 (s, 1 H, COOH). Yield, 3.2 g (37 mol %).

Provenance & Evidence