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Oxy-s-triazine (OST) is one of the important Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) decomposition products, while it is yet not fully clear how it is formed up to now. The study systematically investigates the reaction of s-triazine (TAZ) with nitrate radical (NO3) using computational chemistry methods, for which three entrance channels are devised, resulting in the formation of four isomers of OST. Based on the analysis of the barrier heights and the reaction exothermicities, the pathway to form OST3 through hydrogen atom abstraction and rebound mechanism is likely to be the main channel in the reactions of TAZ with NO3 radical. Our study puts forward a new possible route to generate OST. [ABSTRACT FROM AUTHOR]

The thermite reaction at Al/CuO nano-interfaces is investigated with ab initio molecular dynamics calculations in canonical ensemble at 500 K, 800 K, 1200 K and 1500 K, respectively. The reaction process and reaction products are analyzed in terms of chemical bonds, average charge, time constants and total potential energy. The activity of the reactants enhances with increasing temperature, which induces a faster thermite reaction. The alloy reaction obviously expands outward at Cu-rich interface of Al/CuO system, and the reaction between Al and O atoms obviously expands outward at O-rich interface as temperature increases. Different reaction products are found at the outermost layer of different interfaces in the Al/CuO system. In generally, the average charge of the outer layer aluminum atoms (i.e., Al1, Al2, Al5 and Al6) increases with temperature. The potential energy of Al/CuO system decreases significantly, which indicates that drastic exothermic reaction occurs at the Al/CuO system. This research enhances fundamental understanding in temperature effect on the thermite reaction at atomic level, which can potentially open new possibilities for its industrial application. [ABSTRACT FROM AUTHOR]

The p53 tumour suppressor is activated in response to a wide variety of genotoxic stresses, frequently via post-translational modification. Using a knock in mouse model with a Ser312 to Ala mutation, we show here that phosphorylation of p53 on Ser312 helps to prevent tumour induction by the alkylating agent MNU, which predominantly caused T cell lymphomas. This is consistent with our previous observation that p53312A/A mice are more susceptible to X-ray induced tumourigenesis. Phosphorylation on Ser312 aids p53's interaction with E2F1, and enhances p53-mediated apoptosis. Loss of E2F1 alone does not affect tumour susceptibility to MNU, but its absence partially rescues tumour formation in p53312A/A mice, thus reflecting the oncogenic properties of E2F1. Our data confirms the participation of Ser312 phosphorylation in tumour suppression by p53. [ABSTRACT FROM AUTHOR]

Which is the first step in the decomposition processof nitromethane is a controversial issue, proton dissociation or C–Nbond scission. We applied reactive force field (ReaxFF) moleculardynamics to probe the initial decomposition mechanisms of nitromethane.By comparing the impact on (010) surfaces and without impact (onlyheating) for nitromethane simulations, we found that proton dissociationis the first step of the pyrolysis of nitromethane, and the C–Nbond decomposes in the same time scale as in impact simulations, butin the nonimpact simulation, C–N bond dissociation takes placeat a later time. At the end of these simulations, a large number ofclusters are formed. By analyzing the trajectories, we discussed therole of the hydrogen bond in the initial process of nitromethane decompositions,the intermediates observed in the early time of the simulations, andthe formation of clusters that consisted of C–N–C–Nchain/ring structures. [ABSTRACT FROM AUTHOR]

Abstract: Because secondary explosives are stable molecules with large energy barriers to chemical reaction, in shock or impact initiation, a sizable amount of phonon energy must be converted to the molecular internal higher vibrations by multiphonon up pumping. To investigate the relationship between impact sensitivities and energy transfer rate, the number of doorway modes of explosives is estimated by a simple theory in which the rate is proportional to the number of normal mode vibrations. We evaluated frequencies of normal mode vibrations of 2,4,6-trinitro-m-cresol (C7H5N3O7), picric acid, TNB, TNAP, TNT, TNA, TBN, DATB, and TATB by means of density functional theory (DFT) at the b3p86/6-31g (d,p) level. The number of doorway modes in the regions of 200–700cm−1 was evaluated by the direct counting method. It is found that the number of doorway modes shows a linearly correlation to the impact sensitivities derived from drop hammer tests. This result is in agreement with several previous works. Besides, it is also noted in our study that in those secondary explosives with similar molecular structure and similar molecular weight, the correlation between the impact sensitivity and the number of doorway modes is very high. [Copyright &y& Elsevier]

Metal carbide compound containing highly charged C2q-(q 5, 6) moiety is rather scarce. We show by means of density functional calculations that an unprecedented 4-C26-anion can viably exist as an endohedral Sc4C26cluster in the endofullerene Sc4C2C80. The electronic structure, ionization energy, electron affinity, 13C NMR chemical shifts, vibrational frequencies, and electrochemical redox potentials of this unique endofullerene have been predicted to assist future experimental characterization. [ABSTRACT FROM AUTHOR]

We show, by means of quantum chemical calculations, that the inorganic ions Se2l42+ and S2O42-, whose structures have been long-known and well-characterized, have aromaticity resulting from through-space conjugation, analogous to the aromaticity in the transition states of some pericyclic reactions, such as Cope rearrangements and Diels-Alder reactions. [ABSTRACT FROM AUTHOR]

The viability of 1,3-dipolar cycloadditions of a series of 1,3-dipolar molecules (azomethine ylide, ozone, nitrone, nitrile imine, nitrile ylide, nitrile oxide, diazomethane, and methyl azide) onto the sidewalls of carbon nanotubes has been assessed theoretically by means of a two-layered ONIOM approach. The theoretical calculations predict the following: (i) other than the 18-valence-electron azomethine ylide and ozone, the 16-valence-electron nitrile ylide and nitrile imine are the best candidates for experimentalists to try; (ii) upon 1,3-dipolar cycloaddition, a 1,3-diople molecule is di-σ-bonded to a pair of carbon atoms on the sidewall of SWNT, forming a five-membered ring surface species; (iii) the as-formed 1,3-dipole-SWNT bonding is much weaker than that in the products of the molecular 1,3-DC reactions and can be plausibly broken by heating at elevated temperatures; (iv) the sidewalls of the armchair (n,n) SWNTs (n = 5-10) are subject to the 1,3-DCs of ozone and azomethine ylides; (v) both the 1,3-DC reactivity and retro-1,3-DC reactivity are moderately dependent on the diameters of SWNTs, implying the feasibility of making use of the heterogeneous 1,3-DC chemistry to purify and separate SWNTs diameter-specifically. [ABSTRACT FROM AUTHOR]

The diffusion and thermite reaction process of Al/NiO nanothermite composed of Al nanofilm and NiO nano honeycomb are investigated by molecular dynamics simulations in combination with the ReaxFF. The diffusion and thermite reaction are characterized by measuring energy release, adiabatic reaction temperature, and activation energy. Based on time evolution of atomic configuration and mean square displacement, the initialization of the thermite reaction process of Al/NiO nanothermite results from the diffusion of Al atoms. Under the microcanonical ensemble, it is found that the adiabatic reaction temperature of the thermite reaction process of Al/NiO nanothermite reaches over 5500 K, and activation energy is 8.43 kJ/mol. The release energy of the thermite reaction process of Al/NiO nanothermite is 2.2 kJ/g, which is in accordance with the available experimental value. With the same initial temperature, the adiabatic reaction temperature of the thermite reaction process of Al/NiO nanothermite has a tendency to decrease dramatically as the equivalence ratio increases. On the basis of chemical bond analysis, the initial temperature and equivalence ratio have great effects on the thermite reaction process, but do not significantly affect the average length of Al–Ni nor Al–O bond. Overall, the thermite reaction of film-honeycomb Al/NiO nanothermite is a complicated process instead of a theoretical equation. [ABSTRACT FROM AUTHOR]

The 31P NMR chemical shifts of adsorbed trimethylphosphine oxide (TMPO) and the configurations of the corresponding TMPOHcomplexes on Brønsted acid sites with varying acid strengths in modeled zeolites have been predicted theoretically by means of density functional theory (DFT) quantum chemical calculations. The configuration of each TMPOHcomplex was optimized at the PW91/DNP level based on an 8T cluster model, whereas the 31P chemical shifts were calculated with the gauge including atomic orbital (GIAO) approach at both the HF/TZVP and MP2/TZVP levels. A linear correlation between the 31P chemical shift of adsorbed TMPO and the proton affinity of the solid acids was observed, and a threshold for superacidity (86 ppm) was determined. This threshold for superacidity was also confirmed by comparative investigations on other superacid systems, such as carborane acid and heteropolyoxometalate H3PW12O40. In conjunction with the strong correlation between the MP2 and the HF 31P isotropic shifts, the 8T cluster model was extended to more sophisticated models (up to 72T) that are not readily tractable at the GIAO-MP2 level, and a 31P chemical shift of 86 ppm was determined for TMPO adsorbed on zeolite H-ZSM-5, which is in good agreement with the NMR experimental data. [ABSTRACT FROM AUTHOR]

We present a systematic theoretical investigation on the addition reaction of Grignard reagents to malimides to understand its mechanism as well as the origin of its regio- and diastereo-selectivity. The computations carried out at a hybrid density functional B3LYP/6-31G* level of theory reveal that (i) the addition of Grignard reagents with N,O-dimethylmalimide (1-methyl-3-methoxypyrrolidine-2,5-dione) occurs regioselectivity at the at the α-carbonyl (Cl) by passing through a cis-a-chelated precursor and affords steroselectively cis-addition product, in qualitative agreement with teh previous experimental observations: (ii) such regioselectivity is ascribed to the preferential chelation of Grignard reagent to the α-carbonyl (Cl) over the coordination to the α′-carbonyl (C4). (iii) its unusual trans-addition, in sharp contrast to the Gram chelation-type seteroselectivity for the reaction of aliphatic α- or β-alkoxy caronyl compounds, is due primarily to the rigidity of the five-membered ring skeleton of the malimde that favors the formation of the cis-α-chelated precursor; and (iv) poor regioselectivity is predicted for the reaction of O-TBDMS-protected malimide (1-benzyl-3-tert-butyldimethylsilyloxy)pyrrolidine-2,5-dione with Grignand reagent and can be ascribed to the large sterie repulsion of the bulky TBDMS group and the electonic effects of the silyl group that remarkably destabilizes the α-chelated precursors and the corresponding transition states. [ABSTRACT FROM AUTHOR]

Abstract: Nitrate radical (NO3) is reported to be one of the initial decomposition products of RDX, while it has never been detected in experiment studies. This study for the first time theoretically investigated the reactions of H X CN (X =1,2) with NO3 by computational chemistry methods. The calculated results demonstrate that the barrier height of H abstraction reaction of H2CN with NO3 is close to 0kcalmol−1, implying that the reaction may be responsible for the disappearance of NO3 during the decomposition process of RDX. The study encourages further experimental investigation in future. [Copyright &y& Elsevier]