New Synthetic Methods for 4,4’,5,5’-Tetranitro-2,2’-bi- 1H-imidazole (TNBI)

Four new nitration methods for the synthesis of 4,4’,5,5’-tetranitro-2,2’- bi-1H-imidazole (TNBI) were examined. TNBI was synthesized by nitration of 2,2’-bi-imidazole (BI) with the following mixtures: (CH3CO)2O/HNO3, (CF3CO)2O/ HNO3, P4O10/HNO3 and H3PO4/P4O10/HNO3. Nitration of BI with a mixture of nitric acid and acetic anhydride leads to 4,4’-dinitro-bi-imidazole. The other nitrating conditions investigated gave TNBI in lower yields (6.0-22.4%). Crystallization of crude TNBI from wet ethanol/acetone gave TNBI as its dihydrate. The structures of BI and TNBI were characterized by 1H, 13C and 15N NMR spectroscopy and elemental analysis. Friction and impact sensitivity, detonability and detonation velocity were determined for pure TNBI dihydrate.