Preparation of Imidazolium 2,4,5-Trinitroimidazolate from Derivatives of Imidazole and Its Oxidation Under Nitration Conditions

In this study, the nitration reactions of imidazole and its nitro derivatives with a mixture of 98% HNO₃ and 98% H₂SO₄ (or 15% SO₃ in H₂SO₄) were reinvestigated. When imidazole or 4(5)-nitroimidazole was nitrated with a mixture of 98% HNO₃ and 98% H₂SO₄ (or 15% SO₃ in H₂SO₄), only 4,5-dinitroimidazole was obtained. Imidazolium 2,4,5-trinitroimidazolate was prepared from 2-nitroimidazole or 2,4(5)-dinitroimidazole with a mixture of 98% HNO₃ and 98% H₂SO₄ (or 15% SO₃ in H₂SO₄); the highest yields were 57.8 and 62.8%, respectively. However, on increasing the reaction temperature, duration, amount of H₂SO₄ or HNO₃, the by-product ethanedioic acid was produced. A possible reaction mechanism for the formation of ethanedioic acid from 2,4,5-trinitroimidazole is suggested. The compounds 4,5-dinitroimidazole, imidazolium 2,4,5-trinitroimidazolate and ethanedioic acid were characterized by infrared spectroscopy, multinuclear ¹H and ¹³C NMR spectroscopy, and elemental analysis. The structures of 4,5-dinitroimidazole and ethanedioic acid were further confirmed by single-crystal X-ray diffraction.