Theoretical and experimental vibrational and NMR studies of RDX

The cyclic nitramine hexahydro-1,3,5-trinitro-s-triazine, commonly known as RDX, is a powerful secondary explosive that has attracted considerable attention due to its polymorphism. The conformers of RDX are distinguished mainly by the arrangement of the nitro groups relative to the ring atoms of the RDX molecule. FTIR and Raman spectra of solid RDX and C-13 enriched RDX are presented and assigned with the help of the density functional theory calculations. Chemical shielding constants were computed by gauge independent atomic orbital method (GIAO) for beta-RDX conformer. The data are compared with the experimental solid and solution data, focusing on the agreement the spectral patterns and spectral trends. The results of harmonic vibrational frequencies and absolute shielding (GIAO) calculations using density functional theory approximation supported by experimental studies are reported. The qualitative agreement between the experimental and calculated values of the chemical shifts shed more light on the understanding the basic shift-molecular structure relationship of RDX conformers.