scholarly journals The Role of (H2O)1-2 in the CH2O + ClO Gas-Phase Reaction

Molecules ◽  
2018 ◽  
Vol 23 (9) ◽  
pp. 2240 ◽  
Author(s):  
Junyao Li ◽  
Narcisse Tsona ◽  
Lin Du
Keyword(s):  
Rate Constant ◽  
Density Functional ◽  
Hydrogen Transfer ◽  
Kinetic Studies ◽  
Water Molecules ◽  
Phase Reaction ◽  
Functional Theory ◽  
Molecule Reaction ◽  
Catalytic Role

Mechanism and kinetic studies have been carried out to investigate whether one and two water molecules could play a possible catalytic role on the CH2O + ClO reaction. Density functional theory combined with the coupled cluster theory were employed to explore the potential energy surface and the thermodynamics of this radical-molecule reaction. The reaction proceeded through four different paths without water and eleven paths with water, producing H + HCO(O)Cl, Cl + HC(O)OH, HCOO + HCl, and HCO + HOCl. Results indicate that the formation of HCO + HOCl is predominant both in the water-free and water-involved cases. In the absence of water, all the reaction paths proceed through the formation of a transition state, while for some reactions in the presence of water, the products were directly formed via barrierless hydrogen transfer. The rate constant for the formation of HCO + HOCl without water is 2.6 × 10−16 cm3 molecule−1 s−1 at 298.15 K. This rate constant is decreased by 9−12 orders of magnitude in the presence of water. The current calculations hence demonstrate that the CH2O + ClO reaction is impeded by water.

A Density Functional Theory Study of the Catalytic role of Ti atoms in Reversible Hydrogen Storage in the Complex Metal Hydride, NaAlH4

2005 ◽  
Vol 884 ◽  
Author(s):  
Santanu Chaudhuri ◽  
James T Muckerman
Keyword(s):  
Density Functional Theory ◽  
First Principles ◽  
Molecular Hydrogen ◽  
Density Functional ◽  
First Principles Calculations ◽  
Density Functional Theory Study ◽  
Functional Theory ◽  
Catalytic Role ◽  
Present Part

AbstractPresence of ∼2-4 % Ti is critical for reversible hydrogenation/rehydrogenation in NaAlH4. We have investigated the probable catalytic role of Ti in this complex multi-step process. The present part of our study concentrates on the rehydrogenation reaction, i.e., the reverse reaction that forms NaAlH4 from its constituent binary hydrides. First principles calculations using density functional theory (DFT) show that a particular arrangement of Ti atoms on the surface of Al metal promotes the chemisorption of molecular hydrogen. We also present comparisons with existing experimental data (EXAFS and TEM) to support the existence of such an arrangement on the surface.

scholarly journals Two Faces of Water in the Formation and Stabilization of Multicomponent Crystals of Zwitterionic Drug-Like Compounds

Symmetry ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 425
Author(s):  
Artem O. Surov ◽  
Nikita A. Vasilev ◽  
Andrei V. Churakov ◽  
Olga D. Parashchuk ◽  
Sergei V. Artobolevskii ◽  
...  
Keyword(s):  
Density Functional ◽  
General Scheme ◽  
Density Functional Theory Calculations ◽  
Cooh Group ◽  
Water Molecules ◽  
Intermolecular Hydrogen Bonds ◽  
Functional Theory ◽  
Bader Analysis ◽  
Empirical Approaches

Two new hydrated multicomponent crystals of zwitterionic 2-aminonicotinic acid with maleic and fumaric acids have been obtained and thoroughly characterized by a variety of experimental (X-ray analysis and terahertz Raman spectroscopy) and theoretical periodic density functional theory calculations, followed by Bader analysis of the crystalline electron density) techniques. It has been found that the Raman-active band in the region of 300 cm−1 is due to the vibrations of the intramolecular O-H...O bond in the maleate anion. The energy/enthalpy of the intermolecular hydrogen bonds was estimated by several empirical approaches. An analysis of the interaction networks reflects the structure-directing role of the water molecule in the examined multicomponent crystals. A general scheme has been proposed to explain the proton transfer between the components during the formation of multicomponent crystals in water. Water molecules were found to play the key role in this process, forming a “water wire” between the COOH group of the dicarboxylic acid and the COO– group of the zwitterion and the rendering crystal lattice of the considered multicomponent crystals.

scholarly journals Critical computational analysis illuminates the reductive-elimination mechanism that activates nitrogenase for N2reduction

2018 ◽  
Vol 115 (45) ◽  
pp. E10521-E10530 ◽  
Author(s):  
Simone Raugei ◽  
Lance C. Seefeldt ◽  
Brian M. Hoffman
Keyword(s):  
Electrostatic Interactions ◽  
Density Functional ◽  
Computational Analysis ◽  
Reductive Elimination ◽  
Water Molecules ◽  
Computational Investigation ◽  
Functional Theory ◽  
Elimination Mechanism ◽  
Femo Cofactor

Recent spectroscopic, kinetic, photophysical, and thermodynamic measurements show activation of nitrogenase for N2→ 2NH3reduction involves the reductive elimination (re) of H2from two [Fe–H–Fe] bridging hydrides bound to the catalytic [7Fe–9S–Mo–C–homocitrate] FeMo-cofactor (FeMo-co). These studies rationalize the Lowe–Thorneley kinetic scheme’s proposal of mechanistically obligatory formation of one H2for each N2reduced. They also provide an overall framework for understanding the mechanism of nitrogen fixation by nitrogenase. However, they directly pose fundamental questions addressed computationally here. We here report an extensive computational investigation of the structure and energetics of possible nitrogenase intermediates using structural models for the active site with a broad range in complexity, while evaluating a diverse set of density functional theory flavors. (i) This shows that to prevent spurious disruption of FeMo-co having accumulated 4[e−/H+] it is necessary to include: all residues (and water molecules) interacting directly with FeMo-co via specific H-bond interactions; nonspecific local electrostatic interactions; and steric confinement. (ii) These calculations indicate an important role of sulfide hemilability in the overall conversion ofE0to a diazene-level intermediate. (iii) Perhaps most importantly, they explain (iiia) how the enzyme mechanistically couples exothermic H2formation to endothermic cleavage of the N≡N triple bond in a nearly thermoneutralre/oxidative-addition equilibrium, (iiib) while preventing the “futile” generation of two H2without N2reduction: hydrideregenerates an H2complex, but H2is only lost when displaced by N2, to form an end-on N2complex that proceeds to a diazene-level intermediate.

A catalytic role of surface silanol groups in CO2 capture on the amine-anchored silica support

2018 ◽  
Vol 20 (17) ◽  
pp. 12149-12156 ◽  
Author(s):  
Moses Cho ◽  
Joonho Park ◽  
Cafer T. Yavuz ◽  
Yousung Jung
Keyword(s):  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Proton Transfer Reaction ◽  
Silica Support ◽  
Functional Theory ◽  
Capture Process ◽  
Amine Functionalized ◽  
Catalytic Role ◽  
Amine Groups

A new mechanism of CO2 capture on the amine-functionalized silica support is demonstrated using density functional theory calculations, in which the silica surface not only acts as a support to anchor amines, but also can actively participate in the CO2 capture process through a facile proton transfer reaction with the amine groups.

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