CONTEXT: This project performed quantum chemical computation, through kinetic and thermodynamic analyses to compare relative reactivity, reaction rate, and equilibrium composition from the possible pathways in connection with stabilizer-nitrodioxide reactions to determine the stability of the materials for practical application. Corresponding achievements have promoted the use of N-methyl-p-nitroaniline (MNA) and dinitrophenyl malonamide series (M3, M4, and M5) stabilizers as high priorities for selection. METHODS: The Gaussian 09 program (G09) (Frisch et al 2009) and density functional theory (DFT) calculations with the B3LYP/6-31G(d,p) function were performed to obtain related geometric and thermodynamic energy data for the molecular systems in this study. The synchronous transit-guided quasi-Newton method (STQN) (Peng and Schlegel Isr J Chem 33:49, 1993) was applied through the QST3 procedure to identify single imaginary frequency-valued transition-state species. The related reaction rate constant (k) and pre-exponential factor (A) were obtained, based on transition state theory (Su 2008), using Eqs. 11 and 12.
Molecular dynamics (MD) simulations were carried out to study the physical properties of graphene-oxide (GO) and polydimethylsiloxane (PDMS) interfacial systems. Simulations were performed for GO molecules dispersed into short-chain, long-chain, and long-chain and cross-linked PDMS polymers. Various structural properties, dipole moments and dielectric constants of the graphene-oxide molecules were calculated, which were correlated with the electron transport properties of the GO/PDMS system. The effects of polymer length and type of linkage on transport properties were also examined.
Electron Transport , Graphite/chemistry , Molecular Dynamics Simulation , Nanocomposites/chemistry , Algorithms , Models, Molecular , Molecular Structure
To investigate the effect of low temperature and catalyst filling pattern on the adsorption of Hg° by DeNOx equipment, the chemisorption and kinetic mechanisms of Hg° adsorption on 5-30%V2O5/TiO2 immobilized on glass beads at 100-160 °C were investigated. The effects of the reaction temperature, influent Hg° concentration, and V2O5 doping amount on the adsorption efficiency and capacity for Hg° were explored. The active sites for Hg° adsorption were further identified. Additionally, the adsorption kinetics were modelled using the linear driving force approximation, Fick's diffusion model, and pseudo-second-order kinetic model. Finally, the influence of immobilization on the adsorption of Hg° was also investigated. Experimental results showed that the bridged oxygen atom of V-O-V played a key role in the adsorption of Hg°. The Hg° adsorption efficiencies decreased from >90% to 40% as the reaction temperature increased from 120 °C to 160 °C for 20%V2O5/TiO2, while the adsorptive capacities for Hg° were highly influenced by the influent Hg° concentration and V2O5 doping amount. 20%V2O5/TiO2 had the highest adsorptive capacity of 2547 µg Hg°/g V2O5/TiO2 at 160 °C. The kinetic results showed that the linear driving force approximation model fit the Hg° adsorption better than the other models. The diffusion resistance increased significantly for the immobilized catalysts because the external mass transfer coefficient decreased by more than 1200-fold.
The application of high performance liquid chromatography (HPLC) to separate explosive chemicals was investigated by molecular dynamics (MD) simulations. The explosive ingredients including NG, RDX, HMX and TNT were assigned as solutes, while methanol (CH3OH) and acetonitrile (CH3CN) were assigned as solvents in the solution system. The polymeric-molecular siloxanes (SiC8) and poly-1,2-methylenedioxy-4-propenyl benzene (PISAF) compounds were treated as stationary phase in the simulation. The simulation results showed that the different species of explosive ingredients were separated successfully in the solutions by each of the constructed stationary phase of SiC8 and PISAF after a total simulation time of 12.0 ps approximately, which were consistent with the experimental analysis of HPLC spectra. The origin for the separation was found due to the electrostatic interactions between polymer and explosives.
Chromatography, Liquid , Explosive Agents/chemistry , Explosive Agents/isolation & purification , Molecular Dynamics Simulation , Chromatography, High Pressure Liquid , Molecular Structure , Nanotubes, Carbon/chemistry , Structure-Activity Relationship
In respective water or ethanol polarizable continuum cavity environments, simultaneous aldol condensation was performed using density functional theory (DFT) computational method to model the synthesis of optically active (RS)-1,2,4-butanetriol trinitrate (BTTN). The results of reaction energy barrier analysis suggested feasible routes with lower activation energies to obtain either the (R)- or (S)-configuration product in ethanolic solution. In addition, local analysis of average inter-particulate distances of reaction species revealed that a stronger inter-particulate interaction accompanied a shorter average distance in the ethanol system. The stabilization effect also indicated that related syntheses would be able to proceed in ethanol. Furthermore, relative to the production of (R)-BTTN, a lower overall energy of 425.3 kJ/mol was required for the synthesis of (S)-BTTN. Through analysis of the effects of temperature on the reaction rates of individual parallel stages of (R)- and (S)-species synthesis, it was simple to adjust the reaction temperature accordingly to differentiate between relative rates in order to obtain a product of a specific configuration. Graphical abstract á .
Amorphous molecular simulation to model the reaction species in the synthesis of chemically inert and energetic 1,1-diamino-2,2-dinitroethene (DADNE) explosive material was performed in this work. Nitromethane was selected as the starting reactant to undergo halogenation, nitration, deprotonation, intermolecular condensation, and dehydration to produce the target DADNE product. The Materials Studio (MS) forcite program allowed fast energy calculations and reliable geometric optimization of all aqueous molecular reaction systems (0.1-0.5 M) at 283 K and 298 K. The MS forcite-computed and Gaussian polarizable continuum model (PCM)-computed results were analyzed and compared in order to explore feasible reaction pathways under suitable conditions for the synthesis of DADNE. Through theoretical simulation, the findings revealed that synthesis was possible, and a total energy barrier of 449.6 kJ mol-1 needed to be overcome in order to carry out the reaction according to MS calculation of the energy barriers at each stage at 283 K, as shown by the reaction profiles. Local analysis of intermolecular interaction, together with calculation of the stabilization energy of each reaction system, provided information that can be used as a reference regarding molecular integrated stability. Graphical Abstract Materials Studio software has been suggested for the computation and simulation of DADNE synthesis.
Two synthesis methods were investigated in this study in order to explore feasible reaction pathways to obtain the target DADNE product: (1) the nitration of tetrahalogen ethene and (2) the reaction of acetamidine hydrochloride with dicarbonyl dichloride. Through theoretical simulation, the findings revealed that synthesis was possible, starting from acetamidine hydrochloride in a hydrated environment, followed by subsequent reaction routes via cyclization of the methoxy-substituted acetamidine anion intermediate with oxalyl chloride to form 2-methoxy-2-methyl-imidazolan-4,5-dione, acid-catalyzed synthesis of 2-methylene-imidazolan-4,5-dione, nitration using nitric acid to obtain 2-dinitromethylene-imidazolan-4,5-dione, and hydrolysis to produce 1,1-diamino-2,2-dinitroethene. A total energy of 1048.4 kJ mol(-1) was needed to carry out the reaction according to calculation of the energy barriers at each stage, as shown by the reaction profiles.
