Molecular Structure Parameters Research Articles

Phase equilibrium and separation process of byproduct vinyl acrylate in the ethylene vapor phase method producing vinyl acetate

Vinyl acrylate is one of the byproducts in the ethylene vapor phase method for the production of vinyl acetate (VAc), which not only has a toxic effect on the catalyst but also affects the purity of the product. Currently, phase equilibrium data for vinyl acrylate with water are missing, making the destination of vinyl acrylate in the distillation process uncertain. This has led to a lack of effective removal means, which restricts the optimization of the ethylene vapor phase method. This paper uses a method combining quantum chemistry and molecular dynamics simulation (MD) to investigate the existential form of the water molecule. And based on the ab initio calculation of the first principle, the force field parameters of the special water molecular structure are calculated, and the TIP4P-P force field that can describe the special water structure is established. Using the Gibbs Ensemble Monte Carlo (GEMC) method, the reliability of the improved water molecule force field for modeling the phase equilibrium of a binary system is first verified. Further, vapor–liquid phase equilibrium data for the vinyl acrylate-water binary system at 110 kPa and 150 kPa are calculated and the corresponding x-y and T-x-y phase diagrams are plotted. After performing the thermodynamic consistency test, the phase equilibrium data are fitted to obtain the binary interaction parameters of vinyl acrylate with water. The fitted parameters are applied to the process simulation of the VAc refining process to optimize the conditions and obtain an effective separation scheme for vinyl acrylate. The concentration distribution of vinyl acrylate in the distillation column is investigated, thus clarifying the destination of vinyl acrylate in the distillation process and facilitating the optimization of the ethylene vapor phase method.

Vibrational Spectra and Computational Study of Amyl Acetate: MEP, AIM, RDG, NCI, ELF and LOL Analysis

This work is focused on biologically active neat amyl acetate and its solutions in ethanol/heptane. According to the experimental results, when the concentration of amyl acetate in the amyl acetate-ethanol solution decreases, the additional band appears on the low-frequency side. The primary reason for the formation of such additional band is the intermolecular hydrogen bonding between amyl acetate and ethanol. In the amyl acetate-heptane solution, as the concentration of amyl acetate in the solution decreases, the band corresponding to the C=O stretching vibrations shifted to a higher frequency. This is explained by the fact that heptane breaks intermolecular interactions in solution, resulting in a simpler spectral band corresponding to the C=O stretching vibrations. Calculations are also used to study interactions in amyl acetateethanol complexes and their spectral manifestations. When the complex formation energies are calculated, this energy increases with the number of molecules, but the average hydrogen bond energy per one bond remains unchanged. The density functional theory (DFT) method is used to analyze molecular structural parameters: Mulliken atomic charge distribution; thermodynamic parameters; molecular electrostatic potential (MEP) surface; atoms in molecules (AIM) analysis; quantum chemical parameters such as reduced density gradient (RDG) and noncovalent interaction (NCI) analysis; electron localization functions (ELF) analysis; and localized orbital locator (LOL) analysis.

Mesoporous, high surface area and microrod-shaped cobalt (II) coordination polymer for assessment of molecular structure, thermolysis and non-isothermal kinetics parameters

This study is significant as it presents the assessment of molecular identification, thermal degradation, and non-isothermal kinetics of a cobalt (II) coordination polymer [Co (II) CPs] synthesized from suberoyl bis (2-ethoxybenzamide) (sbebz) and cobalt acetate through the condensation process. The condensation product sbebz was obtained from suberoyl chloride and 2-ethoxybenzamide. The XRD, FT-IR, Raman, and XPS investigated as aspects to identify its structure, purity, and chemical state. The morphological facet was confirmed by SEM and TEM. The morphology data revealed a microrod-shaped morphology of Co (II) CPs with an average particle size 0.7 µm to 1 µm. The pore size, and surface properties were examined by Brunauer-Emmett-Teller (BET) and atomic force microscopy (AFM), revealing a highly large surface area (1076 m2/g), mesoporous and monodisperse nature. The molecular interaction of ligand was estimated using protein molecule. The thermal-decomposition behavior and non-isothermal kinetics of Co (II) CPs were estimated at different heating rates (5 °C/min, 10 °C/min, 15 °C/min, and 20 °C/min) under nitrogen atmosphere by thermogravimetry/Derivative thermogravimetry (TG/DTG). As-synthesized Co (II) CPs show enhanced thermal stability compared to the ligand (sbebz). The multiple heating TG/DTG curve exhibits a more or less identical degradation profile/pattern. The kinetic parameters like order of reaction (n), pre-exponential Arrhenius factor (A), activation entropy (∆s), activation energy (Ea), activation free-energy (∆G), and activation enthalpy (∆H) were calculated using Coats-Redfern (CR) method.

Molecular insights into 5-hydroxymethylfurfural: a computational, spectroscopic, and docking investigation

The quantum chemical properties of 5-hydroxymethylfurfural were investigated using Density Functional Theory alongside vibrational spectroscopy. Key outcomes included optimizing molecular structure, vibrational frequencies, and various molecular parameters. By comparing DFT results with experimental infrared spectra, molecular motion was clarified. Reactive sites were identified through Molecular Electrostatic Potential and Fukui function analyses. Hirshfeld surface analysis revealed insights into the crystal structure’s intermolecular interactions and hydrogen bonding. Time-dependent Density Functional Theory combined with the Polarizable Continuum Model provided Ultraviolet spectra, highlighting charge transfer between the highest occupied and lowest unoccupied molecular orbitals. The compound’s electronegativity (4.7239) and electron affinity were assessed. Biological studies, including drug-likeness evaluations and molecular docking, also demonstrated potential physiological benefits, mainly through the compound’s low binding energy. A 100-nanosecond molecular dynamics simulation of the 5-HMF-4LB4 complex revealed its stability and dynamic behavior through analyses of Root Mean Square Deviation, Root Mean Square Fluctuation, hydrogen bonding, Solvent Accessible Surface Area, and radius of gyration.

Nitroxide Spin Labels for Exploring Relationships Between Molecular Structure, Microenvironment and EPR Parameters: A Mini-review Dedicated to Carlo Corvaja

AbstractThis mini-review is dedicated to Carlo Corvaja (University of Padova) in recognition of his important contributions to the study of biomimetic donor–acceptor model dyads and triads and to the understanding of spin exchange in excited fullerene–nitroxide derivatives. We report on attractive examples of multi-frequency and multi-resonance EPR spectroscopy, highlighting recent work in Padova and Berlin/Mülheim. The examples selected include TR-EPR, ENDOR, and EDNMR experiments on photoexcited spin-labeled macromolecules, such as fullerene–nitroxide complexes or photosynthetic bacterial reaction centers, which were optionally NO spin-labeled. From the spin interaction parameters measured, detailed information about structure and dynamics of macromolecules embedded in liquid-solution or solid-state microenvironments could be extracted.

Molecular docking and DFT study of antiproliferative ribofuranose nucleoside derivatives targeting EGFR and VEGFR2in cancer cells

Antimetabolites are the most effective chemotherapeutics for treating cancer. They have exerted their anticancer effects by interfering with DNA synthesis. Recently, interest in modified nucleoside analogues has grown due to their superior efficiency. Nucleoside analogue derivatives have emerged as crucial candidates for cancer treatment due to their ability to target the cells responsible for cancer within the body specifically. The ability of nucleoside analogues derivatives to target specific molecular pathways has reduced toxicity and increased efficiency compared to traditional chemotherapy drugs. Nucleoside analogues have interfered with physiological nucleosides and induced cytotoxicity in cancerous cells. In this investigation, derivatives of ribofuranose nucleoside analogues have been designed. Density functional theory (DFT) calculations have been performed at the B3LYP/6–311 G(d,p) level. The designed molecules have been characterized by UV/Vis spectroscopy using the CPCM model in DMSO solvent, and molecular structural parameters, such as HOMO/LUMO and MEPS, have been determined. Derivative d1m has exhibited a high energy gap and low absorption energy compared to the other derivatives. Molecular docking of the designed molecules (d1o-d2m) has been performed with the EGFR and VEGFR2 proteins. d2o has shown good binding energy with the EGFR protein, while d1o has shown good results with VEGFR2. Global chemical parameters and NBO analysis have been conducted to investigate the derivatives charge transfer properties and chemical reactivity. NBO analysis has provided information about the donor and acceptor parts within a molecule, while global chemical parameters have given insights into the reactivity, stability, and solubility of the molecules. It has been found that the derivatives are more chemically reactive, thermodynamically stable, and have better binding affinity than the parent molecule. Based on the analysis, the drug interaction with the cancer-causing protein makes it more effective for cancer treatment.

Solubility behavior and solvation effect of a photomechanical molecular crystal trans-4-chlorocinnamic acid in twelve neat solvents at temperatures from 283.15 to 323.15 K

Solubility of trans-4-chlorocinnamic acid as a photomechanical molecular crystal material in twelve pure solvents (water, ethanol, methanol, n-propanol, isopropanol, n-butanol, isobutanol, acetonitrile, 1,4-dioxane, acetone, methyl acetate and ethyl acetate) were measured from 283.15 to 325.15 K at 101.2 kPa. The results showed that the trans-4-chlorocinnamic acid solubility increased with the temperature, the order is: 1,4-dioxane > acetone > n-butanol > ethanol > n-propanol > isopropanol > isobutanol > methanol > methyl acetate > ethyl acetate > acetonitrile > water. Powder X-ray diffraction pattern (PXRD) and differential scanning calorimetry (DSC) were used to identify and characterize the equilibrated solid phase samples. The solubility behavior and the solute–solvent interaction of trans-4-chlorocinnamic acid in each selected mono-solvent were explored by the empirical solvents polarity parameter (ET(30)), hydrogen bonding, cohesive energy density, molecular structure, and Hansen solubility parameters (HSPs). In addition, the experimental solubility data were correlated by the modified Apelblat model and Yaws model, and the fitting results of this models were all satisfactory. The intermolecular forces were determined through molecular simulations, including Hirshfeld surface (HS) and Molecular Electrostatic Potential Surface (MEPS) analysis. The results showed that hydrogen bond can be formed between trans-4-chlorocinnamic acid and the selected solvents, which can help to further explain the dissolution behavior of trans-4-chlorocinnamic acid in the solvents.

The prediction of donor number and acceptor number of electrolyte solvent molecules based on machine learning

Electrolyte solvents have a critical impact on the design of high performance and safe batteries. Gutmann’s donor number (DN) and acceptor number (AN) values are two important parameters to screen and design superior electrolyte solvents. However, it is more time-consuming and expensive to obtain DN and AN values through experimental measurements. Therefore, it is essential to develop a method to predict DN and AN values. This paper presented the prediction models for DN and AN based on molecular structure descriptors of solvents, using four machine learning algorithms such as CatBoost (Categorical Boosting), GBRT (Gradient Boosting Regression Tree), RF (Random Forest) and RR (Ridge Regression). The results showed that the DN and AN prediction models based on CatBoost algorithm possesses satisfactory prediction ability, with R2 values of the testing set are 0.860 and 0.96. Moreover, the study analyzed the molecular structure parameters that impact DN and AN. The results indicated that TDB02m (3D Topological distance based descriptors−lag 2 weighted by mass) had a significant effect on DN, while HATS1s (leverage-weighted autocorrelation of lag 1/weighted by I-state) plays an important role in AN. The work provided an efficient approach for accurately predicting DN and AN values, which is useful for screening and designing electrolyte solvents.

Effect of mixing rate on molecular structure parameters of polybutadiene rubber based on rheology

Effect of mixing rate on molecular structure parameters of polybutadiene rubber based on rheology

New bounds for variable topological indices and applications

One of the most important information related to molecular graphs is given by the determination (when possible) of upper and lower bounds for their corresponding topological indices. Such bounds allow to establish the approximate range of the topological indices in terms of molecular structural parameters. The purpose of this paper is to provide new inequalities relating several classes of variable topological indices including the first and second general Zagreb indices, the general sum-connectivity index, and the variable inverse sum deg index. Also, upper and lower bounds on the inverse degree in terms of the first general Zagreb are found. Moreover, the characterization of extremal graphs with respect to many of these inequalities is obtained. Finally, some applications are given.

Pressure effects on molecular evolution: Differences between vitrinite and inertinite in coal

The difference between vitrinite and inertinite in coal has been regarded as the starting point, and the vitrinite and inertinite stripped from a coal sample were conducted by high-temperature (600 °C and 900 °C) and high-pressure (1.0, 1.5, and 2.0 GPa) experiments. The samples' molecular structure was examined with element analysis, Fourier-transform infrared spectroscopy, and X-ray diffraction. The results reveal that pressure has an inhibitory effect on the evolution of molecular structure at 600 °C, and the vitrinite shows a lower molecular structure evolution degree than inertinite. For the two macerals at 900 °C, with increasing pressure, the molecular structure parameters exhibit opposite regularities to those at 600 °C, and the vitrinite shows a higher molecular structure evolution degree than inertinite. The evolution rate of molecular structures caused by pressure in vitrinite remains consistent under different temperature conditions, whereas that in inertinite exhibits jumping changes. There must be a transition interval between 600 °C and 900 °C that can change the pressure from inhibiting coalification to promoting coalification. When the temperature exceeds the transition interval, pressure can accelerate the molecular structure evolution in vitrinite, causing it to catch up with and surpass the evolution degree of inertinite's molecular structure.

Magnetic Circular Dichroism Elucidates Molecular Interactions in Aggregated Chiral Organic Materials.

Chiral materials formed by aggregated organic compounds play a fundamental role in chiral optoelectronics, photonics and spintronics. Nonetheless, a precise understanding of the molecular interactions involved remains an open problem. Here we introduce magnetic circular dichroism (MCD) as a new tool to elucidate molecular interactions and structural parameters of a supramolecular system. A detailed analysis of MCD together with electronic circular dichroism spectra combined to ab initio calculations unveils essential information on the geometry and energy levels of a self-assembled thin film made of a carbazole di-bithiophene chiral molecule. This approach can be extended to a generality of chiral organic materials and can help rationalizing the fundamental interactions leading to supramolecular order. This in turn could enable a better understanding of structure-property relationships, resulting in a more efficient material design.

Magnetic Circular Dichroism Elucidates Molecular Interactions in Aggregated Chiral Organic Materials

AbstractChiral materials formed by aggregated organic compounds play a fundamental role in chiral optoelectronics, photonics and spintronics. Nonetheless, a precise understanding of the molecular interactions involved remains an open problem. Here we introduce magnetic circular dichroism (MCD) as a new tool to elucidate molecular interactions and structural parameters of a supramolecular system. A detailed analysis of MCD together with electronic circular dichroism spectra combined to ab initio calculations unveils essential information on the geometry and energy levels of a self‐assembled thin film made of a carbazole di‐bithiophene chiral molecule. This approach can be extended to a generality of chiral organic materials and can help rationalizing the fundamental interactions leading to supramolecular order. This in turn could enable a better understanding of structure–property relationships, resulting in a more efficient material design.

Insight into the crystal structure analysis, vibrational studies, reactivities (MESP, HOMO-LUMO, NBO), and the anticancer activities of ruthenium diazide [Ru(POP)(PPh3)(N3)2] complex by molecular docking approach

This present work employs experimental and density functional theory (DFT) computations methods to investigate the structural, electronic, molecular interactions, and molecular docking of a ruthenium diazide [Ru(POP)(PPh3)(N3)2] complex with potential applications in apoptosis regulation. Crystallography analysis was conducted using Hirshfeld surface analysis which illustrated diverse intermolecular and intramolecular interactions, such as C H…O and CC….H respectively. Also, the following interactions and their percentage abundance existed in the complex O…H 1.5 %, C…H 19.9 %, H…H 68.8 %, C…N 0.2 % and N…H 9.9 %. With H…H interaction showcasing as dominant interaction in the complex. The molecular structure, vibrational analysis, and quantum chemical parameters were investigated within the framework of density functional theory at the ωB97XD/def2svp method. Molecular docking of the Ru-complex with receptor proteins involved in apoptosis regulation, including Death Receptor DR5, Estrogen Receptor Alpha (ERα), and Fas receptor, was performed. Results indicate potential interactions with these proteins, suggesting the Ru-complex's role in caspase-mediated apoptosis, particularly in colon and breast cancer cell lines. The investigation provides valuable insights into the reactivity and potential applications of the Ru-complex in cancer treatment.

Computational Analysis of Excited State Intramolecular Hydrogen Atom Transfer and Microsolvation Studies on 8-Acetyl-7-hydroxy-4-methylcoumarin using DFT and TDDFT

The computational calculations were carried out on 8-acetyl-7-hydroxy-4-methyl coumarin (AHM) and its water complex AHM+(H2O)4- [AHMH] at ground and excited states by employing density functional theory (DFT)/specific state time-dependent density functional theory (SS-TDDFT). In AHM and AHMH molecules, there is an intramolecular hydrogen bond between hydroxyl group and acetyl group along with inter-molecular hydrogen bonds in the hydrated molecule. The computational studies of molecular structural parameters, molecular electrostatic potential, natural bond orbital (NBO) analysis, the molecular orbital’s and UV-Vis spectra of both the molecules under polar solvents were explored by B3LYP/cc-pVDZ/PCM/EFP1 method. The intramolecular hydrogen atom transpired between hydroxyl to acetyl group in AHM/AHMH molecules from S0→S1 state but not in S0→S3/S0→S2 states even though the S3/S2 states have significant oscillation strengths. This indicates that intramolecular chage transfer (ICT) occurs within the molecules and it confirmed using potential energy surface (PES) scan studies.

Atomistic Construction of Silicon Nitride Ceramic Fiber Molecular Model and Investigation of Its Mechanical Properties Based on Molecular Dynamics Simulations.

Molecular simulations are currently receiving significant attention for their ability to offer a microscopic perspective that explains macroscopic phenomena. An essential aspect is the accurate characterization of molecular structural parameters and the development of realistic numerical models. This study investigates the surface morphology and elemental distribution of silicon nitride fibers through TEM and EDS, and SEM and EDS analyses. Utilizing a customized molecular dynamics approach, molecular models of amorphous and multi-interface silicon nitride fibers with complex structures were constructed. Tensile simulations were conducted to explore correlations between performance and molecular structural composition. The results demonstrate successful construction of molecular models with amorphous, amorphous-crystalline interface, and mixed crystalline structures. Mechanical property characterization reveal the following findings: (1) The nonuniform and irregular amorphous structure causes stress concentration and crack formation under applied stress. Increased density enhances material strength but leads to higher crack sensitivity. (2) Incorporating a crystalline reinforcement phase without interfacial crosslinking increases free volume and relative tensile strength, improving toughness and reducing crack susceptibility. (3) Crosslinked interfaces effectively enhance load transfer in transitional regions, strengthening the material's tensile strength, while increased density simultaneously reduces crack propagation.

Comparing molecular representations, e-nose signals, and other featurization, for learning to smell aroma molecules.

Recent research has attempted to predict our perception of odorants using Machine Learning models. The featurization of the olfactory stimuli usually represents the odorants using molecular structure parameters, molecular fingerprints, mass spectra, or e-nose signals. However, the impact of the choice of featurization on predictive performance remains poorly reported in direct comparative studies. This paper experiments with different sensory features for several olfactory perception tasks. We investigate the multilabel classification of aroma molecules in odor descriptors. We investigate single-label classification not only in fine-grained odor descriptors ('orange', 'waxy', etc.), but also in odor descriptor groups. We created a database of odor vectors for 114 aroma molecules to conduct our experiments using a QCM (Quartz Crystal Microbalance) type smell sensor module (Aroma Coder®V2 Set). We compare these smell features with different baseline features to evaluate the cluster composition, considering the frequencies of the top odor descriptors carried by the aroma molecules. Experimental results suggest a statistically significant better performance of the QCM type smell sensor module compared with other baseline features with F1 evaluation metric.

De novo unified robust antidiabetic pharmacophores based on biopotent hybrid material: DFT‐assisted design, optimized molecular structure, and understanding mechanism of antidiabetic bioassay

De novo unified robust antidiabetic pharmacophores based on hybrid material were rationally designed, generated, and characterized by spectroscopic evidences and DFT (B3LYP method). These hybrid pharmacophores demonstrated robust antidiabetic activity. Semicarbazones were used for the generation of these hybrid pharmacophores. Semicarbazones of heterocyclic β‐diketones were synthesized by conventional heating as well by green approach (microwave heating). The results obtained from both the approaches have been summarized and compared. Incorporation of dimethyltin(IV) moiety into some semicarbazones of heterocyclic β‐diketones resulted in the formation of biopotent dimethyltin(IV) formulations of the type Me2SnLA where LH2 = , R = −CH3, L(1)H2, Complex 1; R = −CH2CH3, L(2)H2, Complex 2; R = −C6H5, L(3)H2, Complex 3; and R = p‐ClC6H4−, L(4)H2, Complex 4. One representative semicarbazone of heterocyclic β‐diketone (L(4)H2) and its corresponding dimethyltin(IV) complex Me2SnL(4) (Complex 4) were also studied using computational method (DFT‐B3LYP). Optimized molecular structure, bond lengths, bond angles, EHOMO, ELUMO, dipole moment, polarizability, and other global reactivity parameters were calculated. Energy gap (ΔE) of the ligand L(4)H2 and its corresponding complex has also been compared. Optimized molecular structure–antidiabetic activity relationship of two representative ligands and the corresponding complexes has also been studied. The unified hybrid pharmacophores exhibited robust antidiabetic activity.

Effect of Anaerobic Calcium Oxide Alkalization on the Carbohydrate Molecular Structures, Chemical Profiles, and Ruminal Degradability of Rape Straw.

To improve the utilization efficiency of rape straw, anaerobic calcium oxide (CaO) alkalization was conducted, and advanced molecular spectroscopy was applied, to detect the internal molecular structural changes. Rape straw was treated with different combinations of CaO (3%, 5%, and 7%) and moisture levels (50% and 60%) and stored under anaerobic conditions. We investigated the carbohydrate chemical constituents, the ruminal neutral detergent fiber (aNDF) and acid detergent fiber (ADF) degradation kinetics, and the carbohydrate molecular structural features. CaO-treated groups were higher (p < 0.05) for ash, Ca, non-fiber carbohydrate, soluble fiber, and the ruminal degradability of aNDF and ADF. In contrast, they were lower (p < 0.05) for the contents of aNDF, ADF, and indigestible fiber. With CaO levels rising from 3% to 7%, the content of aNDF and ADF linearly decreased (p < 0.05). CaO treatment and anaerobic storage changed the molecular characteristics, including structural parameters related to total carbohydrates (TC), cellulosic compounds (CEC), and structural carbohydrates (STC). Alterations in cellulosic compounds' spectral regions were highly correlated with the differences in carbohydrate chemical constituents and the ruminal digestibility of rape straw. In summary, CaO treatment and anaerobic storage altered the molecular structural parameters of carbohydrates, leading to an enhancement in the effective degradability (ED) of aNDF and ADF in rape straw. From the perspective of processing cost and effectiveness, 5% CaO + 60% moisture could be suggested as a recommended treatment combination.

SARA Characterization and Comparison for the Ultra-Heavy Oil via Combined Analyses

Abstract Structure characterization and comparison of the ultra-heavy oil and its four components are fundamental and crucial. In this work, nuclear magnetic resonance analyses were employed to quantitatively investigate carbon and hydrogen atom distributions. Combined with the gel permeation chromatography, elemental analysis, and X-ray diffraction results, average molecular structure parameters were determined for four components. Besides, an improved Brown–Ladner method was adopted to identify and adjust corresponding structural parameters, which considered influences of both heteroatoms (O, S, and N), and katacondensed and/or pericondensed system assumption on aromatic structures, compared with conventional methods. Moreover, molecular architectures of four components were, respectively, speculated and reconstructed based on this improved method, and the specific comparison reflected a higher accuracy. From this study, it could provide updated understandings of specific component structural information for the ultra-heavy oil to facilitate subsequent oil reactivity and simulation studies.