Density Functional Theory Studies of Hexamethylene Triperoxide Diamine

Abstract

Hexamethylene triperoxide diamine (HMTD) is a powerful initiating explosive belonging to the family of triperoxide energetic materials. Single-crystal X-ray studies of this compound have revealed exactly planar 3-fold coordination about the two bridgehead nitrogen atoms. We have performed density functional theory B3LYP/6-31+G(d) calculations of HMTD to study the electronic nature of this very unusual coordination and to analyze the energetics and structure of this high-energy compound. The calculated geometry of HMTD was found to agree very well with the X-ray data. The vibrational spectrum of this molecule was also calculated and favorably compared to a diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) singlecrystal spectrum.

Helical chirality in hexamethylene triperoxide diamine

“…Wierzbicki and Cioffi, 6 on the basis of a computed CNC of 117.7°for tris-(hydroperoxymethylene)amine (THPMA), concluded the planarity of the nitrogen in HMTD was a result of steric strain, since the nitrogen in THPMA is more pyramidal. Since the nitrogen in THPMA is nowhere near as pyramidal as that of trimethylamine, this conclusion is questionable in any case; but it is clear that calculations at our higher level of theory, and for a chemically somewhat superior acyclic model compound, result in a considerably more planar nitrogen than computed in the earlier work.…”

“…2 Likely because it, like many peroxide explosives, is easily synthesized from commonly available materials, can be used as a primary explosive or detonator, and at the same time is somewhat more stable than most members of this class, it has been implicated in several recent terrorist incidents (Scheme 1). 3 The first deduction of the chemical structure of HMTD has been attributed 4 to Urbanski, and the compound has since been characterized by X-ray crystallography, 5 infrared, 6 Raman, and NMR spectroscopy, 7,8 and computational methods employing density functional theory (DFT). 4,6 Computation indicates the most stable conformation has D 3 symmetry and, remarkable for such a small molecule, is helically chiral ( Fig.…”

“…3 The first deduction of the chemical structure of HMTD has been attributed 4 to Urbanski, and the compound has since been characterized by X-ray crystallography, 5 infrared, 6 Raman, and NMR spectroscopy, 7,8 and computational methods employing density functional theory (DFT). 4,6 Computation indicates the most stable conformation has D 3 symmetry and, remarkable for such a small molecule, is helically chiral ( Fig. 1(a)); the enantiomers have been labeled 4 P-and Scheme 1.…”

“…This preparation produced about 500 mg of HMTD. For NMR samples, 20 mg of HMTD was dissolved in about 0.5 ml of CD 2 Cl 2 or DMSO-d 6 . Solution NMR spectra were acquired at 14 T using a Bruker Avance spectrometer.…”

The 14N quadrupole coupling in hexamethylene triperoxide diamine (HMTD)

“…HMTD is an interesting molecule to the physical chemist; it is helically chiral in solution 2 but crystallizes with disorder 3 in the achiral space group R3m 4 ; the nitrogens lie on the crystallographic threefold axis. It possesses a comparatively planarized tertiary nitrogen, largely a result of the electronwithdrawing character of the peroxide groups ringing its molecular equator.…”