scholarly journals Theoretical Study of the Effect of Water Clusters on the Enol Content of Acetone as a Model for Understanding the Effect of Water on Enolization Reaction

2021 ◽  
Author(s):  
Zahra Tohidi Nafe ◽  
Nematollah Arshadi
Keyword(s):  
Carbonyl Compounds ◽  
Density Functional ◽  
Water Clusters ◽  
Experimental Studies ◽  
Density Functional Theory Calculations ◽  
Energy Difference ◽  
Biochemical Processes ◽  
Small Water ◽  
Effect Of Water ◽  
Practical Conclusion

Abstract The enolization of simple carbonyl compounds is a key reaction for many chemical and biochemical processes. Numerous theoretical and experimental studies have been done to probe aspects of the mechanism of this reaction. In this work, the effect of small water clusters, (H2O)n: n=1-9, on the enol content of acetone is investigated by using density functional theory calculations at the M06 level of theory in the gas and solution phases. The calculations indicated that the formation of hydrogen-bonded assemblies between water clusters and both tautomers of acetone affect the enolization reaction. Among them, the trimeric water cluster has the highest binding energy difference (DEb) in the solution phase and greatly shift the equilibrium in the favor of the enol form. The results also shown that under this condition, the enol content of acetone increased by decreasing the polarity of the solvent. The practical conclusion of this study is that the enol content of carbonyl compounds can be maximized only by addition a defined amount of water.

Polarizability of Pyruvate Anion in Small Water Clusters

2021 ◽  
pp. 2150009
Author(s):  
Victor Ruan ◽  
Arun K. Sharma
Keyword(s):  
Density Functional ◽  
Water Clusters ◽  
Density Functional Theory Calculations ◽  
Basis Set ◽  
Electronic Polarizability ◽  
Dynamic Polarizability ◽  
Field Frequency ◽  
Atmospheric Reactions ◽  
Small Water ◽  
Broad Array

Pyruvate anion is important in a broad array of physicochemical processes ranging from glucose homeostasis to atmospheric reactions. However, the electronic polarizability of the moiety has not been investigated extensively. We present theoretical results from electronic structure calculations on the static and dynamic polarizability of microhydrated pyruvate anions. These investigations were carried out with the CH3COCOO[Formula: see text]n H2O clusters ([Formula: see text]–9) to mimic microhydration conditions. These density functional theory calculations were carried out at the B3LYP/aug-cc-PVTZ level to uncover the optimal geometry of the anion water cluster. Sadlej basis set functions with the B3LYP functional were used to calculate the static and dynamic polarizabilities. Multiple simulated annealing simulations were carried out to discover additional low-lying minima. It is observed that the electronic polarizability varies linearly with the size of the hydrated cluster. Expressions that describe the relationship between the dynamic polarizability and the field frequency are provided for each cluster.

scholarly journals Influence of Varying Functionalization on the Peroxidase Activity of Nickel(II)–Pyridine Macrocycle Catalysts: Mechanistic Insights from Density Functional Theory

Computation ◽  
2020 ◽  
Vol 8 (2) ◽  
pp. 52
Author(s):  
Jerwin Jay E. Taping ◽  
Junie B. Billones ◽  
Voltaire G. Organo
Keyword(s):  
Density Functional Theory ◽  
Proton Transfer ◽  
Density Functional ◽  
Experimental Studies ◽  
Density Functional Theory Calculations ◽  
Catalytic Performance ◽  
Stoichiometric Ratio ◽  
Functional Theory ◽  
Pendant Arm ◽  
Spin Singlet

Nickel(II) complexes of mono-functionalized pyridine-tetraazamacrocycles (PyMACs) are a new class of catalysts that possess promising activity similar to biological peroxidases. Experimental studies with ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid), substrate) and H2O2 (oxidant) proposed that hydrogen-bonding and proton-transfer reactions facilitated by their pendant arm were responsible for their catalytic activity. In this work, density functional theory calculations were performed to unravel the influence of pendant arm functionalization on the catalytic performance of Ni(II)–PyMACs. Generated frontier orbitals suggested that Ni(II)–PyMACs activate H2O2 by satisfying two requirements: (1) the deprotonation of H2O2 to form the highly nucleophilic HOO−, and (2) the generation of low-spin, singlet state Ni(II)–PyMACs to allow the binding of HOO−. COSMO solvation-based energies revealed that the O–O Ni(II)–hydroperoxo bond, regardless of pendant arm type, ruptures favorably via heterolysis to produce high-spin (S = 1) [(L)Ni3+–O·]2+ and HO−. Aqueous solvation was found crucial in the stabilization of charged species, thereby favoring the heterolytic process over homolytic. The redox reaction of [(L)Ni3+–O·]2+ with ABTS obeyed a 1:2 stoichiometric ratio, followed by proton transfer to produce the final intermediate. The regeneration of Ni(II)–PyMACs at the final step involved the liberation of HO−, which was highly favorable when protons were readily available or when the pKa of the pendant arm was low.

scholarly journals Theoretical and Experimental Studies of the Structural, Phase Stability and Elastic Properties of AlCrTiFeNi Multi-Principle Element Alloy

Materials ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 4353
Author(s):  
Li Liu ◽  
Ramesh Paudel ◽  
Yong Liu ◽  
Xiao-Liang Zhao ◽  
Jing-Chuan Zhu
Keyword(s):  
Structural Stability ◽  
Deformation Behavior ◽  
Density Functional ◽  
Low Cost ◽  
Structural Phase ◽  
Experimental Studies ◽  
Density Functional Theory Calculations ◽  
Mixing Enthalpy ◽  
Size Difference ◽  
Valence Electron Concentration

The fundamental challenge for creating the crystal structure model used in a multi-principle element design is the ideal combination of atom components, structural stability, and deformation behavior. However, most of the multi-principle element alloys contain expensive metallic and rare earth elements, which could limit their applicability. Here, a novel design of low-cost AlCrTiFeNi multi-principle element alloy is presented to study the relationship of structure, deformation behavior, and micro-mechanism. This structured prediction of single-phase AlCrTiFeNi by the atomic-size difference, mixing enthalpy ΔHmix and valence electron concentration (VEC), indicate that we can choose the bcc-structured solid solution to design the AlCrTiFeNi multi-principle element alloy. Structural stability prediction by density functional theory calculations (DFT) of single phases has verified that the most advantageous atom occupancy position is (FeCrNi)(AlFeTi). The experimental results showed that the structure of AlCrTiFeNi multi-principle element alloy is bcc1 + bcc2 + L12 phases, which we propose as the fundamental reason for the high strength. Our findings provide a new route by which to design and obtain multi-principle element alloys with targeted properties based on the theoretical predictions, first-principles calculations, and experimental verification.

Insights into the Adsorption of Water and Oxygen on the Cubic CsPbBr3 Surfaces: A First-Principle Study

2021 ◽  
Author(s):  
Xin Zhang ◽  
Ruge Quhe ◽  
Ming Lei
Keyword(s):  
Adsorption Energy ◽  
Density Functional ◽  
Degradation Mechanism ◽  
Perovskite Solar Cells ◽  
Density Functional Theory Calculations ◽  
Adsorbed Water ◽  
Energy Difference ◽  
Device Fabrication ◽  
Water Molecules ◽  
Inorganic Perovskite

Abstract The degradation mechanism of the all-inorganic perovskite solar cells in the ambient environment remains unclear. In this paper, water and oxygen molecule adsorptions on the all-inorganic perovskite (CsPbBr3) surface are studied by density-functional theory calculations. In terms of the adsorption energy, the water molecules are more susceptible than the oxygen molecules to be adsorbed on the CsPbBr3 surface. The water molecules can be adsorbed on both the CsBr- and PbBr-terminated surfaces, but the oxygen molecules tend to be selectively adsorbed on the CsBr-terminated surface instead of the PbBr-terminated one due to the significant adsorption energy difference. While the adsorbed water molecules only contribute deep states, the oxygen molecules introduce interfacial states inside the bandgap of the perovskite, which would significantly impact the chemical and transport properties of the perovskite. Therefore, special attention should be paid to reduce the oxygen concentration in the environment during the device fabrication process so as to improve the stability and performance of the CsPbBr3 based devices.

Rational design of a molecularly imprinted polymer for dinotefuran: theoretical and experimental studies aimed at the development of an efficient adsorbent for microextraction by packed sorbent

The Analyst ◽  
2018 ◽  
Vol 143 (1) ◽  
pp. 141-149 ◽  
Author(s):  
Camilla Fonseca Silva ◽  
Keyller Bastos Borges ◽  
Clebio Soares do Nascimento
Keyword(s):  
Molecularly Imprinted Polymer ◽  
Density Functional ◽  
Rational Design ◽  
Experimental Studies ◽  
Density Functional Theory Calculations ◽  
Imprinted Polymer ◽  
Functional Theory ◽  
Molecularly Imprinted ◽  
Functional Monomers ◽  
Packed Sorbent

In this work, we studied theoretically the formation process of a molecularly imprinted polymer (MIP) for dinotefuran (DNF), by testing distinct functional monomers (FM) in various solvents through density functional theory calculations.

scholarly journals A Facile Strategy to Prepare Small Water Clusters via Interacting with Functional Molecules

2021 ◽  
Vol 22 (15) ◽  
pp. 8250
Author(s):  
Shanmeiyu Zhang ◽  
Yanyan Zhang ◽  
Chongchong Wu ◽  
Hui Yang ◽  
Qiqi Zhang ◽  
...  
Keyword(s):  
Density Functional ◽  
Md Simulation ◽  
Water Clusters ◽  
Sodium Dodecyl ◽  
Water System ◽  
Functional Theory ◽  
Small Water ◽  
Research Fields ◽  
Simulation Calculation ◽  
Oilfield Development

Although small water clusters (SWCs) are important in many research fields, efficient methods of preparing SWCs are still rarely reported, which is mainly due to the lack of related materials and understanding of the molecular interaction mechanisms. In this study, a series of functional molecules were added in water to obtain small water cluster systems. The decreasing rate of the half-peak width in a sodium dodecyl sulfate (SDS)–water system reaches ≈20% at 0.05 mM from 17O nuclear magnetic resonance (NMR) results. Based on density functional theory (DFT) and molecular dynamics (MD) simulation calculation, it can be concluded that functional molecules with stronger negative electrostatic potential (ESP) and higher hydrophilicity have a stronger ability to destroy big water clusters. Notably, the concentrations of our selected molecule systems are one to two magnitudes lower than that of previous reports. This study provides a promising way to optimize aqueous systems in various fields such as oilfield development, protein stability, and metal anti-corrosion.

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