N. I. Golovina

Phase transformations of 2,4,6,8,10,12-hexanitrohexaazaisowurtzitane: the role played by water, dislocations, and density

A comparative study of the kinetics and mechanisms of the α → γ and ɛ → γ polymorphic transitions in polycrystalline haxanitrohexaazaisowurtzitane was performed using electron and optical microscopy, calorimetry, IR spectroscopy, and quantitative X-ray phase analysis. The kinetics of both processes is complex because of the morphology of the crystals, their defect structure, and impurities. As distinct from the ɛ → γ process, which always occurs as a single crystal-polycrystal transition (through nucleation by the dislocation mechanism with subsequent movement of the phase separation front), the α → γ process can also follow the quasi-homogeneous mechanism and occur as a single crystal-single crystal transition.

Synthesis and structure of di(NON-azoxy)formals and some relatedN-alkyl-N′-alkoxydiazeneN-oxides

A series of di(NON-azoxy)formals and some relatedN-alkyl-N′-alkoxydiazeneN-oxides were prepared by the reaction ofN-nitrosohydroxylamine salts with dihaloalkanes. The dependence of the yield of di(methyl-NON-azoxy)formal on the reaction conditions and the nature of the cation was studied. The structure of di(methyl-NON-azoxy)formal and di(phenyl-NON-azoxy) formal as well as of the coppertert-butylnitrosohydroxylaminate was established by X-ray diffraction analysis.

5,5-Bis(alkoxy-NNO-azoxy)-1,3,2-dioxathiane 2-oxides. Synthesis and X-ray diffraction study

Abstract2,2-Bis(alkoxy-NNO-azoxy)propane-1,3-diols reacted with thionyl chloride to give previously unknown 5,5-bis(methoxy-NNO-azoxy)- and 5,5-bis(ethoxy-NNO-azoxy)-1,3,2-dioxathiane 2-oxides. Replacement of the hydroxy groups by chlorine is a minor reaction path. According to the X-ray diffraction data, the heteroring in the molecule of 5,5-bis(methoxy-NNO-azoxy)-1,3,2-dioxathiane 2-oxide adopts a chair conformation with axial orientation of the S=O bond.

A new crystalline HMX polymorph: ɛ-HMX

A new crystalline HMX polymorph, ɛ-HMX, was obtained. ɛ-HMX crystals were studied by X-ray structure analysis, optical microscopy, and differential scanning calorimetry. Their space group is P21/c. The unit cell parameters are a = 21.799(3) Å, b = 10.913(2) Å, c = 10.819(2) Å, and β = 97.43(2)°, V = 2552.15 Å3, Z = 4. ɛ-HMX molecules are not equivalent in crystals and have chair conformations. The heat of the polymorphic transition of ɛ-HMX into the δ-polymorph was measured. The transition occurred with the intermediate formation of β-HMX. The dependence between the heats of polymorphic transitions and the densities of crystals of various HMX polymorphs was demonstrated. The character of this dependence was to a substantial extent determined by the type of HMX molecule conformation.

The energy parameters of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane polymorphs and their phase transitions

The calculated dispersion and electrostatic intermolecular interaction energies in crystals of γ, α(H2O), and ɛ polymorphs of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazawurtzitane (HNIW) were compared. Preliminarily, nonempirical quantum-chemical calculations of the three compounds with complete geometry optimization were performed using the GAUSSIAN-03 package and density functional theory. The dispersion intermolecular interaction energy was calculated with the “6-exp” potential. The van der Waals and dipole-dipole interaction energies were substantially different in crystals of different HNIW polymorphs, but total energy changes in phase transitions were close to zero. The calculated ɛ > γ and α(H2O) > γ phase transition energies were close to the experimental values determined using a differential calorimeter. Dehydration substantially influenced the kinetics and heat effects of polymorphic transitions.

Kinetics and mechanism of a polymorphous transition in polycrystalline ε-hexanitrohexaazaisowurtzitane

Optical and electron microscopy, calorimetry, IR spectroscopy, and XRD analysis were used to study the ε → γ polymorphous transition in polycrystalline hexanitrohexaazaisowurtzitane. The kinetics of the process is extremely complex due to the intrinsic morphological features and defects in individual crystals in the polycrystalline sample. A limiting phenomenon, which manifests itself in a sharp slowdown of the process at a critical temperature, was revealed. The polymorphous transformation is triggered by dehydration, the removal of the residual water from the crystal. It was demonstrated that dislocations play an important role in the process under study.

Synthesis and the crystal structures of N-(2-nitroxyethyl)isonicotinamide and its complexes with PdCl2 and PtCl2 as potential antitumor medicines

Previously unknown N-(2-nitroxyethyl)isonicotinamide was synthesized by the reaction of isonicotinoyl chloride with 2-nitroxyethylamine and was used as a ligand in the reactions with PdCl2 and PtCl2 to prepare new complexes, viz., trans-bis[(2-nitroxyethyl)isonicotinamide-N]dichloropalladium(ii) and cis-bis[(2-nitroxyethyl)isonicotinamide-N]dichloroplatinum(ii), respectively. The structures of the ligand and the resulting complexes were established by X-ray diffraction analysis.

Structural and electronic parameters of some cyclic nitramines

Conclusions1.X-ray diffraction strctural analyses were repeated for 1,3,3,5,7,7-hexanitro-1,5-diazacyclooctane and the β form of 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane.2.The electronic structure of three cyclic nitramines was studied and the distribution of intermolecular contacts was analyzed for their crystals.3.The total charges on the nitro groups atoms in the molecules studied differ. The molecular packing in the crystals and, thus, their density depend significantly on the electronic parameters of the individual molecules.

Structure of 5-methyl- and 5,5-dimethyl-2,8-dioxa-3,4,6,7-tetraaza-3,6-nonadiene 4,6-dioxide

Conclusions1.The structures of 5-methyl- and 5,5-dimethyl-2,8-dioxa-3,4,6,7-tetraaza-3,6-nonadiene 4,6-dioxide have been established.2.The N=N, N → 0, and N-O bond lengths in these compounds have values intermediate between those for single and double bonds, as a result of p-π conjugation.3.The CN+ (O−)=NOC fragment in these molecules is planar, and has the Z-configuration, stabilized by p-π and n-σ* conjugation.

Kinetics and mechanism of the thermal decomposition of keto-RDX

The thermal decomposition of keto-RDX occurs through the homolysis of the N-NO2 bond in one of the nitramide groups. This bond is substantially longer (1.438 Å) than the analogous bond in the RDX molecule (1.382 Å). The activation parameters of the decomposition, E (kcal/mol) and logA [s−1] were found to be 36.2 and 14.8 in benzene and 35.4 and 12.84 in the solid phase. In the latter case, the reaction proceeds through the dislocation mechanism. The crushing of large crystals produces no effect on the decomposition rate, which, however, depends on the regime of crystallization. The rearrangement into unstable diazoxy esters, a process typical of linear nitramides, does not occur in keto-RDX because of steric hindrances.