Thermal Decomposition of Energetic Materials XVIII. Bis (cyanomethyl)nitramine and Bis(cyanoethyl)nitramine

The crystal structures of two potentially useful cyanonitramines are reported. Bis(cyanomethyl)nitramine (BCMN), (NCCH₂)₂NNO₂: monoclinic, C2, a = 10.247(1), b = 7.771(1), c = 12.230(2) Å], β = 107.45 (2)^°, Z = 6, D_calc = 1.502 g.cm⁻³, R_F = 2.8%, R_wF = 3.1%. A syn (C₂) and anti (C_s) isomers of BCMN crystallize together in a 2:1 ratio in the unit cell. Bis(cyanoethyl)nitramine (BCEN), (NCCH₂CH₂)NNO₂: monoclinic, P2₁/c, a = 7.512(2), b = 10.840(3), c = 10.181(3) Å], β = 97.39(2)^°, Z = 4, D_cale = 1.357 g.cm⁻³, R_F = 4.6%, R_wF = 4.7%. Only one conformation of the BCEN molecule having no symmetry is present in the unit cell. The IR spectrum shows that BCEN forms an amorphous phase when the melt is cooled or when an acetone or acetonitrile solution is rapidly evaporated. The amorphous phase slowly crystallizes at room temperature. High-rate thermolysis of BCMN liberates NO₂ as the predominant initial product. This difference is qualitatively predictable on the basis of the variation in the N-N bond distance in these two compounds.