Physical Chemistry Research
Volume:5 Issue: 4, Autumn 2017

In this study explosive substance [2.4.6] three Nitro Toluene (TNT) was attached with nanostructures of fullerene (C24) and boron nitride nano-cages (B12N12). After that using B3LYP (Becke, three-parameter, Lee-Yang-Parr), a method from density functional theory (DFT), thermodynamic parameters of TNT with foregoing nanostructures, in different conditions of temperature, were computed. To this aim, the materials on both sides of suggested synthesis reactions were geometrically optimized, and then, the calculations of the thermodynamic parameters were done on all of them. The values of enthalpy(ΔH), Gibbs free energy(ΔG) and Specific heat capacity(Cv) for these reactions were computed, also various parameters such as energy levels, the amount of HOMO/LUMO values and related parameters including electrophilicity scale, chemical hardness, chemical potential, and the maximum amount of electronic charge transferred were computed, Finally, the effect of type and Molecular weight of nano structure fullerene ( C24, B12N12) on explosion properties and other chemical properties of TNT were evaluated.

The goal of this research was to study the curing behavior and biodegradability DER 736 modified with epoxidized oleic acid. In this paper we demonstrate the efficient epoxidation of oleic acid with performic acid generated in situ from formic acid and hydrogen peroxide in the presence of H2SO4 as catalyst. The highest relative epoxy yield of 61% was achieved at 40 ͦC after 10 h. DER 736 modified with epoxidized oleic acid was thermally cured using succinic anhydride as curing agent, in the presence of triethylamine. Also, degradation of new composite studied in the presence of three different loadings of epoxidized oleic acid (0, 20, and 40 wt %) with lipase from porcine pancreas in phosphate buffer. It was found that this agent caused reducing the weight of the samples in 45 days. SEM studies also revealed higher surface erosion phenomenon and structural change of the matrix with increasing epoxidized oleic acid.

Vibration-rotation and pure rotational data in the X2Σ ground state and electronic data from the A2Π – X2Σ and B2Σ − X2Σ transitions of CaH and CaD were used in the quantum-mechanical direct-potential-fit (DPF) analysis to determine an analytic potential energy function for the X2Σ ground state of CaH, and a radial correction function for the CaD isotopologue. The potential energy function for the X2Σ state reproduces all the observed energy levels of CaH and CaD within their experimental uncertainties. In addition, it follows the ab initio potential very closely outside the data region, and has the theoretical long-range behavior near the asymptote.

In this research, SBA-15/Polypyrrole (SBA-15/PPy) mesoporous nanocomposite was synthesized, characterized and applied for Acid Blue 62 (AB62) adsorption as a textile dye from aqueous solution. In order to evaluate the structural properties of synthesized adsorbent, FT-IR, FESEM and TEM images, XRD, and BET techniques were applied. Some parameters such as pH, dosage, and time which affect the batch adsorption process were investigated and optimized as well. The optimized condition was achieved by 0.3 g/l adsorbent at pH = 2 and 60 min in contact. In addition, Langmuir, Freundlich, Temkin, Dubinin–Radushkevich (D-R) and Redlich–Peterson (R-P) adsorption isotherms were employed to determine type of adsorption isotherm. The results showed the agreement of experimental data with Langmuir adsorption isotherm with maximum dye 1428.571 mg/g adsorption capacity. The kinetic analysis was carried out by pseudo-first-order, pseudo-second-order, intra-particle diffusion and Elovich models. The results revealed that the adsorption kinetic is more similar to the pseudo -second-order. The parameters of thermodynamic like ΔH°, ΔG°, and ΔS° were calculated. The ΔG° and ΔH° negative values and ΔS° positive values (5.155 J/mol K) illustrated that AB62 adsorption process is physi-sorption, spontaneous, exothermic and feasible.

“Malaria” is a life-threatening blood disease in tropical regions that spreads by the bite of the Anopheles mosquito. Antimalarial medications are designed to cure or prevent this infection, and prosperous achievements in this area mostly depend on the knowing the drug-receptor interactions and active sites of medicine. This improvement can be achieved through understanding the electronic structure of compounds using calculated quadrupolar parameters of nuclei as an efficient theoretical method. In this research, conjugated hydrazones as new antimalarial drugs are investigated to find the correlation between their electronic structures and pharmaceutical behavior. To this aim, the effect of the various substituents and their position on quadrupolar parameters and charge distributions are examined by concepts of nuclear quadrupole resonance (NQR) spectroscopy. The results show that benzothiazole hydrazones are multi-central inhibitors. In addition to the charge density on N13 atom, the presence of two vicinal oxygen atoms with high electron density in the benzene ring has the key role in the iron chelating and consequently antimalarial activity of these compounds. All calculations are performed at the HF/6-31G* level of theory using the Gaussian 03 program.

The main objective of this work is to upgrade a diesel oil sample from Shiraz Oil Refining Co. (SORC) to reduce the sulfur content, as well as to break the kinematic viscosity of the feedstock. Effects of several operating parameters including volume of hydrogen peroxide/acetic acid as an oxidant mixture, amounts of tetraoctylammonium bromide as a phase transfer agent (PTA) and phosphotungstic acid as a transition metal catalyst (TMC) and time were first screened using two-level factorial design and then optimized with the Box- Behnken scheme. It was shown that the kinematic viscosity cannot be substantially reduced due to the low power generated by the ultrasonicator. In addition, irradiation time has the least effect on desulfurization efficiency of the oil among the parameters studied in this work. Moreover, results showed that at optimal conditions of 13.17 ml hydrogen peroxide, 17.26 ml acetic acid, 0.15 g PTA and 1.5 g catalyst, a sulfur removal of 60.75% is attained which in turn could be increased to more than 68% by using a single-stage extraction step in the wake of the main ultrasound-assisted oxidative desulfurization (UAOD) process.

Metallo-β-lactamases (MβL) catalyzing the hydrolytic cleavage of the four-membered β-lactam ring in broad spectrum of antibiotics and therefore inactivating the drug; However, the mechanism of these enzymes is still not well understood. Electronic structure and electronic energy of metallo-β-lactamase active center, two inhibitors of this enzyme including penicillin and cephalexin, and different complexes between these inhibitors and active center of metallo-β-lactamase have been investigated. For both substrates (S), the nucleophilic attack of the substrate amide group to model’s active site dinuclear zinc (E) formed an ES reactive complex that by passing through the first transition state (TS1), first intermediate (INT1), the second intermediate (INT2) and second transition state (TS2) converted to the product. Also, all the thermodynamic functions, ∆Hº, ∆Sº and ∆Gº, to form two transition states, TS1 and TS2, and for the total reaction for two MβL inhibitors are evaluated at 25 °C and 1 atmosphere pressure. In all calculations, solvent effects have been considered in water using PCM method.

The governing mechanism of surface reactions is a fundamental concern in heterogeneous catalysis. The Langmuir–Hinshelwood (LH) mechanism is widely accepted to control the surface reactions in many catalytic systems. This contribution derives and compares several important surface rate equations to evaluate their quality of fitting to the experimental data collected for a vapor-phase hydrogenation case study to produce furfuryl alcohol over supported copper catalysts. Meanwhile, a few essential but less addressed issues in determining the surface reaction mechanism were underlined. It is established that the Eley–Rideal mechanism would be equally (if not more) viable compared to the LH rate model all with coefficients of multiple determination larger than 97%, a conclusion in some contradiction with the common assumption of the previous publications for this case study. This investigation further highlighted that a good fit to any rate expression should not be taken as a proof of the assumed mechanism unless the opponent cases are tested within adequately wide ranges of concentrations.

Herein, a theoretical study on the stability of some vic-dioxime complexes of Ni(II), Pd(II) and Pt(II) in gas and aqueous phases is reported. The DFT/M06/SDD and DFT/M06/6-31G+(d,p) levels of theory were adopted for the metal ions and for every other element respectively. Structural analyses of investigated complexes have revealed square planar geometries stabilized by two O–H⋯Cl hydrogen bonds. Analysis of hydrogen bond energies calculated via quantum theory of atoms in molecules (QTAIM) and computed chemical hardness values has revealed that the stability of the complexes is determined by the hydrogen bond strength. Natural population analysis has revealed ligand-metal charge transfer in the complexes investigated. A good linear agreement with correlation coefficient 0.992 has been found between calculated and experimental IR vibrational frequencies, indicating the validity of the theoretical method employed herein. Negative binding energies obtained are indicative of the stability of the complexes, thus affirming the use of vic-dioximes ligands as potential d8 transition metal eliminating agents in solution.

The kinetics of reaction between 4-methylaniline (1), dimethyl acetylenedicarboxylate (2) and formaldehyde (4) has been theoretically investigated to gain further insight into the reaction mechanism. The results of theoretical calculations were achieved using the ab initio method at the HF/6-311g (d, p) level of theory in gas phase. The mechanism of this reaction had 5 steps. Theoretical kinetic data (k and Ea), activation parameters (∆G#, ∆S# and ∆H#) and thermodynamic parameters (∆G̊, ∆S̊ and ∆H̊) were calculated for each step and overall reaction. Step 2 of the mechanism was identified as the rate determining step. Also, the method of calculations was improved to B3LYP/6-311g (d, p) level of theory and the reaction mechanism was investigated for all steps of this reaction, again kinetic data and thermodynamic parameters were recalculated at this level of the theory. Improved data at this level was in a good agreement with the HF/6-311g (d, p) level of theory. Theoretical results, altogether were compatible with the literature's reports. As expected, step1 and step3 were recognized as the fast and fastest steps among the other steps. The overall reaction was enthalpy-controlled and proceeded chemically-controlled. In addition, step4 was recognized as a relatively slow, due to the five-membered ring formation in this step was inherently an energetically unfavorable.

In this paper, ab initio calculations were performed on the ternary complex formed by HB(CO)2, XCN (X = Cl, Br) and YF (Y = Li, H, Cl). In these complexes boron act as a non-classical electron donor to form a unconventional halogen bond. The cooperative effect between the B•••X halogen bond and lithium/hydrogen/halogen bond was investigated. The calculated results show that the B•••X and N•••Y interactions in the termolecular complexes are stronger compared with those in their corresponding bimolecular complexs. The cooperativity energies of these termolecular complexes span a range, from -1.06 to -2.75 kJ /mol and -1.63 to -4.34 kJ /mol for X = Cl and Br, respectively, which indicates the presence of the cooperativity effect. The nature of interactions is analyzed in terms of parameters derived from molecular electrostatic potential (MEP), natural bond orbital (NBO) and atoms in molecules (AIM) analyses. The amount of charge transfer in the termolecular complexes is stronger compared with those in their corresponding bimolecular complexs. The obtained results from AIM analyses demonstrate that B•••X bond and N•••Y bond in the termolecular complexes are amplified compared to the bimolecular complexs.

In this work, the mean activity coefficients of KCl in the KCl+lactose +water system were determined using the potentiometric method. The electromotive force measurements were carried out on the galvanic cell without liquid junction of the type: Ag|AgCl|KCl (m), lactose (wt.%), H2O (1−wt.) %|K-ISE, in various mixed solvent systems containing 0, 5,7.5, 10 and 12.5 % mass fractions of lactose. The ionic strengths range was from 0.0003 to 2.000 kg.mol−1. The modeling of this ternary system was made based on the Pitzer ion-interaction model. The mean activity coefficients were correlated with Pitzer model and the adjustable Pitzer parameters (βo, β1 and Cø) were determined for the series under investigated system. Then, these parameters were used to calculate the amounts of thermodynamic properties such as osmotic coefficients and excess Gibbs free energies for under investigated systems. The results clearly indicated that a good correlation was obtained with the Pitzer model to describe this system.

Thiosemicarbazones (TSCs) possess significant antimalarial properties believed to be linked to the inhibition of major cysteine proteases, such as falcipain-2, in Plasmodium falciparum. However, the binding modes of TSCs to the active site of these enzymes are not clear. As a result of this, the nature of the bonding interactions between the active site of falcipain-2 and different derivatives of acetophenone thiosemicarbazone (APTSC) and propiophenone thiosemicarbazone (PPTSC) acting as inhibitors, have been studied herein via topological analyses of electron density. Derivatives of APTSC and PPTSC are well known to possess inhibitory effects against Plasmodium falciparum. Equilibrium geometries of the inhibitor–active site complexes in the aqueous phase have been obtained via dispersion-corrected density functional theory (DFT-D3) calculations. In-depth analyses of the covalent and noncovalent interactions in these complexes have been performed using the quantum theory of atoms in molecules (QTAIM) and the noncovalent interaction (NCI) index. Results have revealed a covalent interaction between the thiocarbonyl carbon of the TSC moiety and the thiolate sulfur of the active site cysteine residue of falcipain-2. Moreover, hydrogen bonding, dispersive-like van der Waals and π-stacking interactions have been elucidated between the TSC moiety of each inhibitor and the histidine residue of the enzyme’s active site. The synergy of these interactions can enable the TSCs studied herein to specifically but transiently bind to the active site residues of falcipain-2. Based on our results, APTSC and PPTSC derivatives are potential reversible covalent inhibitors of falcipain-2, and are therefore promising precursors for the manufacture of antimalarial drugs.

Plumbylenes are reactive intermediates whose discovery and characterizations are of great significance. Here, ten novel plumbylenes are introduced and characterised. A comparison is made between novel 1,4-di(R)tetrazol-5-plumbylenes (IR) with their corresponding 1,3-di(R) isomers (IIR), at DFT (R = H, Me, Et, i-Pro, and t-Bu). Every one of our plumbylenes (IR or IIR) appears less stable, with a lower band gap (ΔΕHOMO-LUMO), and a higher nucleophilicity (N) than its corresponding carbene (I´R or II´R). For both IR and IIR plumbylenes the trend of N values emerges consistent with the size of substituents (t-Bu > i-Pro > Et > Me > H). Every IIR shows a higher N than its corresponding IR. Except IIH, every IIR emerges more aromatic than its related IR. The N of both IR and IIR appears directly proportional to the size of R, proton affinity (PA), and plumbylene bond angles (N—((Pb) ̈ ) ̂—N); while it is inversely proportional to electrophilicity (ω), and ΔΕHOMO-LUMO.

In this study, the theoretical calculations of CO dissociation were carried out on Cu-Fe alloy surface by a full-potential method, which made more accurate results especially on the prediction of adsorption energies. This process may be governed by either a direct route or a H-assisted via HCO and COH intermediates pathways. In comparison to the pure surface Fe (100), the presence of Cu atom enhanced the activation energy of direct dissociation pathway and decreased that one for H-assisted mechanism through the HCO intermediate by 0.2eV and 0.24eV respectively. These effects were explained completely by the ligand effect and the ensemble effect corresponding to the electronic and geometrical activity of an adsorption-site on different states (initial, intermediate, and final).In this case, Cu impurity atom creates 3-fold-Fe-hollow site instead of 4-fold–Fe-hollow site on the surface as ensemble effect and Fe atoms near the Cu atom show more reactivity according to the ligand effect. The results showed that while both methods, CO-direct dissociation and H-assisted, are feasible on Fe (100) surface, only the later one happens on Fe-Cu surface. The results of this study suggest that Fe-Cu surface with moderate trend for adsorption has a higher life expectancy compared to Fe (100) due to the higher CO-direct dissociation-activation energy to build carbide. Also, by changing the main route from direct to H-assisted, the activity of Fischer- Tropsch reaction is enhanced with lower activation energy versus that one on Fe (100) surface.