Modelization by molecular mechanics (and X‐rays) of five‐membered heterocyclic nitramines

Molecular Mechanics (MM) calculations and X‐ray structures are compared for 1,4‐dinitro tetraazabicyclo(3,3.0)octanedione [1,4‐dinitro glycoluryl = 1,4‐DINGU]; 1,3‐dinitro‐4,6‐diacetyl tetraazabicyclo(3.3.0)octanedione [1,3‐dinitro‐4,6‐diacetyl glycoluryl = 1,3‐DINDAGU]; and 2,5,7,9‐tetranitro tetraazabicyclo(3.4.0)non‐anone (K 56). The agreement between geometries obtained by MM and X‐ray is good. The structure and the conformational states of the three model molecules are discussed. 1.4‐DINGU and K 56 are more symmetrical by MM than by X‐ray; this is due (at least in part) to packing in the crystal lattice. The parameters to be used in MM calculations, for treating stretching, bending and eclipsing forces in nitramines are given.