Nitrogen-15 Solid-State NMR Study of RDX and HMX-Polymorphs

Abstract

The study of the molecular structure and conformation of explosive materials in the solid state is more relevant to the explosive behavior than the structure in solution. The recently developed high-resolution, solid-state NMR techniques, namely cross polarization, magic angle rotation and high power proton decoupling, have been applied to obtain N-15 NMR spectra of the important nitramine explosives, RDX and HMX, enriched in N-15 content. The spectra of RDX and the four polymorphs of HMX are clearly distinguishable and show promise of interesting correlations with the charge densities on the nitrogens of each conformation in the crystal structure derived from molecular orbital calculations. These spectra represent some of the first few solid-state N-15 NMR spectra available in the literature.