Pentanitromonoformylhexaazaisowurtzitane (PNMFIW) was synthesized by the nitrolysis of tetraacetyldiformylhexaazaisowurtzitane (TADFIW) in mixed nitric and sulfuric acids and structurally characterized by element analysis, FF-IR, MS and H-1 NMR. Single crystals of PNMFIW were grown from aqueous solution employing the technique of controlled evaporation. PNMFIW belongs to the orthorhombic system having four molecules in the unit cell, with space group P2(1)2(1)2(1) and the lattice parameters a = 8.8000(18) angstrom, b = 12.534(2) angstrom, and c = 12.829(3) angstrom. The calculated density reaches 1.977 g/cm(3) at 93 K, while the experimental density is 1.946 g/cm(3) at 20 degrees C. The calculated detonation velocity and pressure of PNMFIW according to the experimental density are 9195.76 m/s and 39.68 GPa, respectively. PNMFIW is insensitive compared with epsilon-HNIW through drop hammer impact sensitivity test. (C) 2009 Elsevier B.V. All rights reserved.