Nitramine Molecules Research Articles

Interactions between a neutral polymeric bonding agent and nitramine explosives and their influencing factors

Neutral polymer bonding agents (NPBAs) have proven highly effective in enhancing the interfacial bonding between the bonding matrix and nitramine explosives such as cyclic trimethylene trinitramine (RDX) and cyclic tetramethylene trinitramine (HMX). However, there is a lack of clear understanding of the mechanisms behind their interactions, and it has been found that NPBAs produce different interfacial bonding effects on RDX and HMX. To gain deeper insights into the molecular-scale interfacial interactions of nitramine explosives/NPBAs, this study investigated the molecular electrostatic potentials, intermolecular interactions, surface structural features, and interfacial adsorption of a NPBA onto nitramine explosives using the density functional theory and molecular dynamics (MD) technique. The results indicate that the N atom on the cyano group of the NPBA molecule can form weak hydrogen bonds C–H⋅⋅⋅NC and C–H⋅⋅⋅O with the H atoms in the RDX and HMX molecules. The strength of such weak hydrogen bonding interactions is affected by the electrostatic potential range of nitramine molecules. Additionally, the surface structure of the nitramine plays a critical role in the NPBA adsorption strength. Compared to HMX, RDX exhibits a narrower surface electrostatic potential range and smoother crystal surface, resulting in weaker intermolecular interactions between the NPBA and the RDX surface.

Towards the thermal reactivity and behavior of co-agglomerated crystals of DATB and TATB with attractive nitramines

The thermolysis of the co-agglomerates (CACs) of the attractive nitramines RDX, BCHMX, HMX and CL-20 with 1,3-diamino-2,4,6-trinitrobenzene (DATB) and 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) was studied by means of differential thermal analysis (DTA) and differential scanning calorimetry (DSC), using the Kissinger method for output evaluation. The insertion of both DATB and TATB molecules into nitramine crystal lattices markedly increased the thermal sensitivity of the resulting CACs to overheating. Depression in melting points was detected in all CACs and, with the exception of RDX CACs, also in the exothermic peaks. The RDX CACs differ from the other studied CACs by their decomposition in the liquid state. The activation energies (Ea), obtained correlate with asymmetric N-O stretching vibrations, confirming the important influence of ‒N‒O····H‒H= interactions in CACs; a similar correlation with asymmetric NO2 stretching confirms the interactions of DATB and TATB molecules with nitramine molecules through van der Waals forces. The insertion of DATB or TATB into the crystal lattice of HMX or CL20 changes their polymorphic modification from β- to δ- and in the latter case from ɛ- to β- modifications in the corresponding CACs. The correlations of the Ea values with the square of detonation velocity as a representative of performance and with the heat of combustion as a representative of the energy content are consistent with already previously described relationships of this type, including exceptions for pure nitramines.

Theoretical simulation study on crystal property and hygroscopicity of ADN doping with nitramine explosives (RDX, HMX, and CL-20).

To effectively modify the strong hygroscopicity of ammonium dinitramide (ADN) crystal, the modification of ADN crystal in the 298K under vacuum environment was studied through theoretical calculation. Three kinds of energetic nitramine molecules (X = RDX, HMX, and CL-20) were inserted into ADN crystal in different proportions (the molecular ratios of ADN to X are 6/1, 12/1, 18/1, and 24/1), to form a total of 12 kinds of designed ADN crystals. The results show that with the modification of ADN crystal with RDX, HMX, and CL-20, the crystal space group, cell parameters, crystal density, and growth morphology will be changed under vacuum conditions. According to the analyses of adsorption heat data, four proportional modification systems all reduced the hygroscopicity of ADN crystal to varying degrees. It is worth noting that the hygroscopicity of modified ADN crystal tends to decrease with the increase of the proportion of doping molecules, but the stability gradually deteriorates, especially 18ADN/1CL-20 and 24ADN/1CL-20. Although they have an excellent anti-moisture effect, from the perspective of crystal energy stability, the actual syntheses of these two kinds of crystal cells are the most difficult. Combined with the energy stability and hygroscopicity analysis, 1HMX/24ADN crystal is a more suitable anti-hygroscopicity modification scheme among the doped ADN crystals. In this case, the isothermal adsorption heat of ADN crystal decreases from 0.692kcal/mol to 0.573kcal/mol. The theoretical simulation study of ADN doping modification in a vacuum will provide significant references for ADN modification in the actual situation.

Quantifying bond strengths via a Coulombic force model: application to the impact sensitivity of nitrobenzene, nitrogen-rich nitroazole, and non-aromatic nitramine molecules.

The quantification of bond strengths is a useful and general concept in chemistry. In this work, a Coulombic force model based on atomic electric charges computed using the accurate distributed multipole analysis (DMA) partition of the molecular charge density was employed to quantify the weakest N-NO2 and C-NO2 bond strengths of 19 nitrobenzene, 11 nitroazole, and 10 nitramine molecules. These bonds are known as trigger linkages because they are usually related to the initiation of an explosive. The three families of explosives combine different types of molecular properties and structures ranging from essentially aromatic molecules (nitrobenzenes) to others with moderate aromaticity (nitroazoles) and non-aromatic molecules with cyclic and acyclic skeletons (nitramines). We used the results to investigate the impact sensitivity of the corresponding explosives employing the trigger linkage concept. For this purpose, the computed Coulombic bond strength of the trigger linkages was used to build four sensitivity models that lead to an overall good agreement between the predicted values and available experimental sensitivity values even when the model included the three chemical families simultaneously. We discussed the role of the trigger linkages for determining the sensitivity of the explosives and rationalized eventual discrepancies in the models by examining alternative decomposition mechanisms and features of the molecular structures.

A new look on the electric spark sensitivity of nitramines

Abstract Electric spark energy, EES, for a 50% probability of initiation of the 14 nitramines was determined using a measuring instrument in which the electrodes are in direct contact with the sample. Indirectly proportional relationships were established between the logarithm of the EES values and the length of the longest N–N bond in the nitramine molecule. This finding is compatible with the mechanism of the first step in the electro-reduction of the nitramine grouping. Directly proportional relationships were found to exist between the EES values and the crystal lattice free volumes, ΔV (i.e. an increase in the ΔV values increases the nitramine's resistance to electric sparks) but there were several nitramines with the opposite course of this relationship. Also a semilogarithic relationships between the EES values and a ratio of intrinsic volumes of molecule, Vint, to the ΔV values were described as well as ambiguous linear dependence between these energies and a sum of the positive and negative extremes of the molecular surface electrostatic potentials, VS,Σ. Several nitramines studied (always the same ones) display roughly the same distribution in the coordinate systems of relationships with lengths of the longest N–N bonds, the Vint/ΔV ratio and the sum VS,Σ as the independent variables. It was found that, typically, such relationships start from a single identical point, in effect a point corresponding to data for a structural unit from which the studied nitramines can be hypothetically generated, and/or are converging on another point, often the one corresponding to the data for HNIW. All the findings point to a fundamental influence of the intermolecular forces on reactivity of nitramines exposed to electric sparks.

Thermo-analytical study of glycidyl azide polymer and its effect on different cyclic nitramines

In this work, glycidyl azide polymer (GAP) has been prepared and studied. In addition, a series of different plastic bonded explosive (PBXs) based on GAP were prepared using five cyclic nitramines, namely. 1,3,5-trinitro-1,3,5-triazinane (RDX) and β-1,3,5,7-tetranitro-1,3,5,7-tetrazocane (β-HMX), cis-1,3,4,6-tetranitrooctahydroimidazo-[4,5-d]imidazole (BCHMX), RS-ε-2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (RS-ε-CL-20) and 4,10-dinitro-2,6,8,12-tetraoxa-4,10-diazaisowurtzitane (TEX). The thermal behavior and decomposition kinetics have been investigated by means of the nonisothermal TG and DSC techniques and the decomposition kinetics were obtained by the isoconversional methods (Kissinger and modified Kissinger-Akahira-Sunose (KAS) methods). It was indicated that GAP has a significant effect on the activation energy distribution for the thermal decomposition of cyclic nitramines and it motivates the initial autocatalysis effect of RDX and CL-20. The mean activation energies of the thermal decomposition were reduced comparing with the individual nitramines, and their values are 187.7, 191.6, 110.7, 118.5, 283.8, 146.1, and 171.6 kJ mol−1 for BCHMX/GAP, CL-20/GAP, RDX/GAP, HMX/GAP peak 1, HMX/GAP peak 2, TEX/GAP and GAP respectively. The GAP admixture changes an inversely proportional linear relationship between the mentioned energies and longest lengths of the NN bonds in nitramine molecules into a directly proportional one for the nitramines in the GAP-PBXs due to the possibility of the GAP complex formation with the studied nitramines. The results show that BCHMX/GAP has a good thermal stability reached the same level of TEX/GAP while the thermal stability of RDX/GAP considered the lowest value of all the studied PBXs.

Crystal lattice free volume in a study of initiation reactivity of nitramines: Friction sensitivity

The relationship between friction sensitivity (FS) and the crystal lattice free space per molecule, ΔV, of thirteen nitramines is described by a linear equation, divided into a number of the partial relationships with strong limitations by their molecular structure characteristics. Increasing FS due to raising of the ΔV values is not clearly confirmed. The influence of the ΔV values on friction sensitivity of nitramines is similar to that of their aza atoms which influence the mutual orientations of nitro groups in neighboring molecules. The dipole-dipole interaction of the oxygen and nitrogen atoms of nitro groups in neighboring nitramine molecules has a major effect on their own FS. In accordance with this interaction, a directly proportional relationship was derived between FS and the intrinsic gas phase molecular volume, Vint, of the nitramines mentioned, which is divided also into several straight lines according to relatively tight molecular structure similarity. The relationships found again confirm a level of disorder in the distribution of the forces in the crystal lattice of the “common” quality of ε−2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane, in comparison with its reduced sensitivity (RS) or chemically pure analogue.

Ab initio multiple spawning dynamics study of dimethylnitramine and dimethylnitramine-Fe complex to model their ultrafast nonadiabatic chemistry.

Conical intersections are now firmly established to be the key features in the excited electronic state processes of polyatomic energetic molecules. In the present work, we have explored conical intersection-mediated nonadiabatic chemical dynamics of a simple analogue nitramine molecule, dimethylnitramine (DMNA, containing one N-NO2 energetic group), and its complex with an iron atom (DMNA-Fe). For this task, we have used the ab initio multiple spawning (AIMS) dynamics simulation at the state averaged-complete active space self-consistent field(8,5)/6-31G(d) level of theory. We have found that DMNA relaxes back to the ground (S0) state following electronic excitation to the S1 excited state [which is an (n,π*) excited state] with a time constant of approximately 40 fs. This AIMS result is in very good agreement with the previous surface hopping-result and femtosecond laser spectroscopy result. DMNA does not dissociate during this fast internal conversion from the S1 to the S0 state. DMNA-Fe also undergoes extremely fast relaxation from the upper S1 state to the S0 state; however, this relaxation pathway is dissociative in nature. DMNA-Fe undergoes initial Fe-O, N-O, and N-N bond dissociations during relaxation from the upper S1 state to the ground S0 state through the respective conical intersection. The AIMS simulation reveals the branching ratio of these three channels as N-N:Fe-O:N-O = 6:3:1 (based on 100 independent simulations). Furthermore, the AIMS simulation reveals that the Fe-O bond dissociation channel exhibits the fastest (time constant 24 fs) relaxation, while the N-N bond dissociation pathway features the slowest (time constant 128 fs) relaxation. An intermediate time constant (30 fs) is found for the N-O bond dissociation channel. This is the first nonadiabatic chemical dynamics study of metal-contained energetic molecules through conical intersections.

Probing the effect of nitro groups in nitramine based energetic molecules: a DFT and charge density study

The structure, electron density distribution, energetic and electrostatic properties of simple nitramine based energetic TMA, DMNA, MDA and TNA molecules were determined using density functional theory (B3LYP) with the 6-311G** and aug-cc-pVDZ basis sets coupled with Bader's theory of atoms in molecules. In the NO2 group substituted molecules, the N–N bond distance increases with the increase of NO2 groups, whereas in C–N bonds, this effect is relatively less, and the distances are almost equal. The topological analysis of electron density reveals that the electron density ρbcp(r) of C–N and N–N bonds are significantly decreasing with the increase of NO2 groups in the nitramine molecules. The Laplacian of electron density ▽2ρbcp(r) of N–NO2 bonds [DMNA: − 16.7 eÅ− 5, MDA: − 12.8 eÅ− 5 and TNA: − 7.9 eÅ− 5] of the molecules are relatively less negative, and the values also decrease with the increase of NO2 groups; this implies that the charge concentration decreases with the increase of NO2 groups, which leads to weakening the N–N bonds of the molecules. The isosurface of molecular electrostatic potential displays high electronegative regions around the NO2 groups. The oxygen balance OB100 of the molecules increases as the number of NO2 group increases in the molecules, in which, the TNA molecule having maximum OB100 value [+7.89]. The band gap, heat of detonation, bond dissociation energy and charge imbalance are predominantly depends on the number of NO2 group present in the molecule. The charge imbalance parameter (ν) has been calculated for all molecules, which reveals that TNA is a highly sensitive molecule, the corresponding ν value is 0.047.

Aminoxyl (Nitroxyl) Radicals in the Early Decomposition of the Nitramine RDX

The explosive nitramine RDX (1,3,5-trinitrohexahydro-s-triazine) is thought to decompose largely by homolytic N-N bond cleavage, among other possible initiation reactions. Density-functional theory (DFT) calculations indicate that the resulting secondary aminyl (R2N·) radical can abstract an oxygen atom from NO2 or from a neighboring nitramine molecule, producing an aminoxyl (R2NO·) radical. Persistent aminoxyl radicals have been detected in electron-spin resonance (ESR) experiments and are consistent with autocatalytic "red oils" reported in the experimental literature. When the O-atom donor is a nitramine, a nitrosamine is formed along with the aminoxyl radical. Reactions of aminoxyl radicals can lead readily to the "oxy-s-triazine" product (as the s-triazine N-oxide) observed mass-spectrometrically by Behrens and co-workers. In addition to forming aminoxyl radicals, the initial aminyl radical can catalyze loss of HONO from RDX.

Neural networks study on the correlation between impact sensitivity and molecular structures for nitramine explosives

In this paper, a back-propagation neural network has been utilized to study on the correlation between impact sensitivity and molecular properties of 33 nitramine molecules. By using density functional theory method B3P86/6-31G**, all the molecular properties have been calculated. Eight different sets of molecular properties, including (HOMO−LUMO)*BDE, E, BDE/E, HOMO−LUMO, BDE*μ, R2, ΔE, and BDE, have been used to train and test the network. Based on the test results, the correlation order between the molecular properties and impact sensitivity has been achieved. The correlation order shows that the input set with the descriptor ΔE(atomization energy) can obtain better results than any other descriptor for nitriamines, which surely accounts for a comparatively stronger correlation between ΔE(atomization energy) and impact sensitivity for nitramines we have studied in this work.

Relationship between Electronic Charges at Nitrogen Atoms of Nitro Groups and Thermal Reactivity of Nitramines

Thermal reactivity of eleven nitramines has been examined by means of non-isothermal differential thermal analysis, and the data were analyzed according to the Kissinger method. The reactivity was expressed as the E a R −1 slopes of the Kissinger relationship. Electronic charges, q N, at nitrogen atoms of the nitramine molecules were calculated by means of ab initio DFT B3LYP/6-31G** method. The relationships were confirmed between the slopes E a R −1 and the q values for the nitro groups that are primarily split off. Conclusions are made in relation to the mechanism of initiation of polynitro compounds in general.

The β–δ phase transition in the energetic nitramine octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine: Thermodynamics

In this and the accompanying paper [L. Smilowitz et al., J. Chem. Phys. 117, 3789, 2002] we present a theoretical treatment and experimental study, respectively, of the β–δ solid state phase transition in the organic nitramine molecule octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX). The transition is thermodynamically first order with a measured latent heat, occurs via nucleation and growth, and exhibits a thermally activated rate of transformation. We construct a two state kinetic model of the system consisting of equilibrium terms first order in the β or δ mole fraction simulating nucleation, and second order in β and δ simulating growth. The model has four rate constants, the temperature dependence of which is described by eight parameters. We use the transition state formulation of the rate constants and apply a thermodynamic model of the activated state that associates the difference in activated state free energy in forward and reverse directions with the equilibrium transition free energy, and identifies the activated state of the growth process with a metastable melt. By associating components of the activated state free energy with independently measured thermodynamic energies we reduce the degrees of freedom to three, which we fix initially by comparison with previously published kinetic data. We apply the model to both the β–δ and δ–β transformations over a temperature range from 300 to 700 K in order to assess the theoretical validity of the model. The model reproduces the half time of the transition over this entire range, spanning conversion times from 106 to 10−4 s. In the accompanying paper we present an experimental study of the kinetics and mechanism of the phase transition based on second harmonic generation spectroscopy. We use second harmonic generation to verify the nucleation and growth mechanism of the transition and measure the mole fraction change with time over a wide range of temperatures. We use the set of parameters established by theoretical considerations in this paper as an initial parameter set and determine an optimized set by comparison with these data.

The β–δ phase transition in the energetic nitramine-octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine: Kinetics

In this paper we present second harmonic generation (SHG) experiments designed to confirm the mechanism and quantify the transformation kinetics of the β–δ solid state phase transition in the organic nitramine molecule octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX). The β phase adopts a centrosymmetric crystallographic configuration (P21/c) while the δ phase adopts a noncentrosymmetric one (P61(P65)). As expected, this results in a very poor generation of SHG intensity from the β phase, while the δ phase is very efficient, rivaling KH2PO4 in absolute efficiency. SHG thus provides a very high sensitivity zero background probe of the δ phase. We discuss the use of this signal as a quantitative measure of the δ phase mole fraction in ensembles of free HMX crystals and crystals embedded in a visco–elastic polymer matrix. We report imaging experiments where the spatial characteristics of the transformation are shown to be consistent with nucleation from a low density of initial sites, followed by rapid growth. We also report experiments where the total integrated SHG is measured and used to infer the transition progress as a function of time in a series of isothermal experiments on both β–δ conversion and δ–β reversion. Additionally, reversibility experiments are reported which are used to verify both the volumetric mechanism of SHG generation in this system and the independence of these results to the internal stress state of the polycrystalline samples. We compare the measured SHG intensity as a function of time for a range of temperatures with predictions of the two state kinetic model presented in the accompanying paper [B. F. Henson et al., J. Chem. Phys. 117, 3780 (2002)]. We perform a set of parameter optimization calculations based on agreement with the predictions of the model. Optimization does not significantly change the kinetic parameters that are thermodynamically constrained by the model, but there is a distribution of parameters necessary to reproduce the nucleation kinetics observed. In particular, a striking difference in nucleation kinetics is observed between samples of free crystals and crystals embedded in a visco–elastic polymer matrix.

Acidity and basicity of primary N‐phenylnitramines: catalytic effect of protons on the nitramine rearrangement

AbstractPara‐substituted N‐phenylnitramines were prepared either by oxidation of diazonium salts or by nitration under alkaline or acidic conditions. Isotopic [15N‐NO2] labelling indicated that the bands characteristic of the N‐nitro group appear in the 1318–1323 and 1585–1607 cm−1 regions. In the nitrogen NMR spectra, the nitramino group gives two resonances at −193 ± 3 (NH) and −32 ± 3 ppm (NO2). The chemical shifts in proton and carbon NMR spectra are predictable, based on increments and the additivity rule. The spectral data indicate the lack of conjugation between the nitramino group and another substituent bound to the ring. It seems to contradict the well‐known fact that substituents strongly (ρ = 4) influence the rate of nitramine rearrangement. The acidities of primary N‐phenylnitramines (3.77 < pKA < 5.62) are similar to those of benzoic acids and weakly dependent (ρ = 1) on the electronic character of a substituent. Based on the analogy with benzoic acids, it has been calculated that basicities of nitramines (pKB ≈ 21) are extremely low. Consequently, addition of protons to an intact nitramine molecule, as the preliminary step of the rearrangement, seems to be improbable. Migration of the N‐nitro group precedes protonation; the latter process facilitates transformation of intermediates into stable final products. Copyright © 2001 John Wiley & Sons, Ltd.

Theoretical Studies of Solid Nitromethane

A classical potential to simulate the dynamics of a nitromethane crystal as a function of temperature and pressure is described. The intramolecular part of the potential was taken as superposition of bond stretching, bond bending, and torsional angles terms. These terms were parametrized on the basis of the geometric and spectroscopic (vibrational frequencies and eigenvectors) data obtained using ab initio molecular orbital calculations performed at the B3LYP/6-31G* level on an isolated molecule. The intermolecular potential used is of the Buckingham 6-exp form plus charge−charge Coulombic interactions and has been previously developed by us (Sorescu, D. C.; Rice, B. M.; Thompson, D. L. J. Phys. Chem. 1997, B101, 798) to simulate crystals containing nitramine molecules and several other classes of nitro compounds. The analyses performed using constant pressure and temperature molecular dynamics simulations and molecular packing calculations indicate that the proposed potential model is able to reproduce accurately the changes of the structural crystallographic parameters as functions of temperature or pressure for the entire range of values investigated. In addition, the calculated bulk modulus of nitromethane was found in excellent agreement with the corresponding experimental results. Moreover, it was determined that the present potential predicts correctly an experimentally observed 45° change in methyl group orientation in the high-pressure regime relative to the low-temperature configuration. The analysis of the linear expansion coefficients and linear compression data indicate anisotropic behavior for the unit cell edges.

Relationship between detonation characteristics and 15N NMR chemical shifts of nitramines

The paper presents 15N NMR chemical shifts δ of twenty three nitramines out of which 1-nitro-1-azaethylene (DIGEN), 1,3-dinitro-1,3-diazacyclobutane (TETROGEN) and 1,3,5,7,9-pentanitro-1,3,5,7,9-pentaazacyclodecane (DECAGEN) have not been synthesized yet. The corresponding δ values of these three substances have been predicted. The relationship has been confirmed between squares of detonation velocities or, as the case may be, the detonation heats and δ values of nitrogen atoms in nitro group of the nitramines. This relationship represents a certain form of Evans-Polanyi-Semenov equation and such it directly specifies the most reactive nitro group of nitramine molecule in the detonation and, hence, the N-NO2 bond primarily split in this process.

Vibrational spectra and conformations of bis(N-ethyl)nitramine molecule

The Raman (50–3200cm−1) and infrared (50–3200cm−1) spectra of bis(N-ethyl)nitramine, (CH3CH2)2NNO2, in the liquid and crystal states have been recorded. Optimized geometries and conformational stabilities have been obtained from ab initio calculations utilizing the RHF/6-31G∗∗ level. This compound was shown to have two stable conformations with a planar nitramine fragment and the CH3 groups orthogonal to it and located either on the same or on the different sides of it. The computed energy difference between two conformers is 0.57kcal/mol. (CH3CH2)2NNO2 exists as a mixture of the two conformations in the liquid state, while only the most stable one, with the CH3 groups located on the different sides of the nitramine fragment, remains in crystal state. The vibrational frequencies have been calculated using ab initio scaled force fields, and the vibrational spectra have been interpreted in detail.

Spin trapping of nitrogen dioxide radical from photolytic decomposition of nitramines

The photochemical ( λ < 400 nm) decomposition of some monocyclic and polycyclic nitramines produces .NO 2, which can be detected in the respective nitramine crystals at 77 K by EPR (electron paramagnetic resonance). In solutions of perdeutero-dimethylsulfoxide (DMSO-d 6) the spintrapped by the solvent to give a radical having the structure CD 3(SO 2)(NO .)CD 3. In this article, we examine this reaction for two nitramines: cyclotrimethylenetrinitramine (RDX) and hexanitrohexaazaisowurzitane (HNIW), which are energetic materials. The decay of the spin-adduct radical (I) follows first-order kinetics for both nitramines studied, having a rate constant ( k) of ≅ 7.1 × 10 −4s ∮1. The net growth in spin concentration of (I) measured from EPR spectra is fitted by a first-order ra equation taking into account the simultaneous competitive decay rate of spin adduct (I). Using the rate data and EPR spin concentration data, the ratio of free .NO 2 produced per parent nitramine molecule is estimated as 1 : 1 for RDX and 4 : 1 for HNIW. Biological implications of trapping of .NO 2 by dimethyl sulfoxide are discussed.

An ab initio study of some nitramine molecules

Ab initio self-consistent field (SCF) molecular orbital calculations have been performed for a series of nitramine molecules. Calculations were conducted on trinitramine, methyldinitramine, methylchloronitramine and trimethylamine using Pople's 6-3IG and 6-3IG ∗ basis sets. Gas phase geometries for these molecules were determined by a minimum energy criterion using gradient techniques. The results are in qualitative agreement with the geometries derived from electron diffraction studies and microwave spectroscopy. The extra-long NN bonds in methyldinitramine and methylchloronitramine were not computed accurately at the SCF level of theory and it was shown that these bonds become longer if electron correlation is included at the second-order Moller-Plesset level. Computations were performed for the heat of formation for trinitramine using Pople's isodesmic reaction concept and compared with a value obtained using an additivity rule.