Quantum Chemical and Kinetic Studies of N2O Formation during Interaction between Char(N) and NO: Influence of Oxygen, Active Sites, and Nitrogen Status

2021 ◽  
Author(s):  
Shanhui Zhao ◽  
Xiaolong Bi ◽  
Miaomiao Niu ◽  
Haiming Gu ◽  
Rongyue Sun ◽  
...  
Keyword(s):  
Quantum Chemical ◽  
Active Sites ◽  
Kinetic Studies ◽  
Nitrogen Status ◽  
N2o Formation

Dimerization of Substituted Arylacetylenes—Quantum Chemical Calculations and Kinetic Studies

2018 ◽  
Vol 83 (15) ◽  
pp. 7878-7885 ◽  
Author(s):  
Sven Fabig ◽  
Alexandra Janiszewski ◽  
Martin Floß ◽  
Mathis Kreuzahler ◽  
Gebhard Haberhauer
Keyword(s):  
Quantum Chemical Calculations ◽  
Quantum Chemical ◽  
Kinetic Studies

Quantum chemical study of the nature of active sites in catalytic trimerization of isocyanates

1983 ◽  
Vol 18 (3) ◽  
pp. 292-296
Author(s):  
N. V. Kozak ◽  
Yu. N. Nizel'skii ◽  
Yu. A. Tishchenko ◽  
T. �. Lipatova
Keyword(s):  
Quantum Chemical ◽  
Active Sites ◽  
Quantum Chemical Study ◽  
Chemical Study

Hydroxylation of C–H bonds at carboxylate-bridged diiron centres

2005 ◽  
Vol 363 (1829) ◽  
pp. 861-877 ◽  
Author(s):  
Stephen J Lippard
Keyword(s):  
Active Sites ◽  
Bond Activation ◽  
Kinetic Studies ◽  
Methyl Radical ◽  
Α Subunit ◽  
Model Complexes ◽  
Soluble Methane Monooxygenase ◽  
Related Enzyme ◽  
High Valent ◽  
Rate Limiting

Nature uses carboxylate-bridged diiron centres at the active sites of enzymes that catalyse the selective hydroxylation of hydrocarbons to alcohols. The resting diiron(III) state of the hydroxylase component of soluble methane monooxygenase enzyme is converted by two-electron transfer from an NADH-requiring reductase into the active diiron(II) form, which subsequently reacts with O 2 to generate a high-valent diiron(IV) oxo species (Q) that converts CH 4 into CH 3 OH. In this step, C–H bond activation is achieved through a transition state having a linear C⋯H⋯O unit involving a bound methyl radical. Kinetic studies of the reaction of Q with substrates CH 3 X, where X=H, D, CH 3 , NO 2 , CN or OH, reveal two classes of reactivity depending upon whether binding to the enzyme or C–H bond activation is rate-limiting. Access of substrates to the carboxylate-bridged diiron active site in the hydroxylase (MMOH) occurs through a series of hydrophobic pockets. In the hydroxylase component of the closely related enzyme toluene/ o -xylene monooxygenase (ToMOH), substrates enter through a wide channel in the α-subunit of the protein that tracks a course identical to that found in the structurally homologous MMOH. Synthetic models for the carboxylate-bridged diiron centres in MMOH and ToMOH have been prepared that reproduce the stoichiometry and key geometric and physical properties of the reduced and oxidized forms of the proteins. Reactions of the diiron(II) model complexes with dioxygen similarly generate reactive intermediates, including high-valent species capable not only of hydroxylating pendant C–H bonds but also of oxidizing phosphine and sulphide groups.

The Pyrolysis of 3-Picoline: Ab Initio Quantum Chemical and Experimental (Shock Tube) Kinetic Studies

1996 ◽  
Vol 36 (3) ◽  
pp. 239-248 ◽  
Author(s):  
Jeffrey Jones ◽  
George B. Bacskay ◽  
John C. Mackie
Keyword(s):  
Shock Tube ◽  
Ab Initio ◽  
Quantum Chemical ◽  
Kinetic Studies ◽  
Experimental Shock

scholarly journals Rate-determining processes and the number of simultaneously active sites of d-glyceraldehyde 3-phosphate dehydrogenase

1971 ◽  
Vol 122 (1) ◽  
pp. 71-77 ◽  
Author(s):  
D. R. Trentham
Keyword(s):  
Oxidative Phosphorylation ◽  
Active Sites ◽  
Dissociation Constants ◽  
Kinetic Studies ◽  
Competitive Inhibitor ◽  
Low Ph ◽  
Conformation Change ◽  
High Ph ◽  
Rate Determining Step ◽  
Transient Experiments

Transient kinetic studies of the reversible oxidative phosphorylation of d-glyceraldehyde 3-phosphate catalysed by d-glyceraldehyde 3-phosphate dehydrogenase show that all four sites of the tetrameric lobster enzyme are simultaneously active, apparently with equal reactivity. The rate-determining step of the oxidative phosphorylation is NADH release at high pH and phosphorolysis of the acyl-enzyme at low pH. For the reverse reaction the rate-determining step is a process associated with NADH binding, probably a conformation change, at high pH and d-glyceraldehyde 3-phosphate release at low pH. NADH has previously been shown to be a competitive inhibitor of the enzyme with respect to d-glyceraldehyde 3-phosphate and vice versa. This is consistent with the mechanism deduced from transient experiments given the additional proviso that 1-arseno-3-phosphoglycerate has a half-life of about 1min or longer at pH7. The dissociation constants of d-glyceraldehyde 3-phosphate and 1,3-diphosphoglycerate to the NAD+-bound enzyme are too large to measure but are nevertheless consistent with the low Km values of these substrates.

scholarly journals The quantum-chemical basis of the catalytic reactivity of transition metals

1992 ◽  
Vol 341 (1661) ◽  
pp. 269-282 ◽  
Keyword(s):  
Quantum Chemical ◽  
Oxidation Reaction ◽  
Active Sites ◽  
State Of The Art ◽  
Reaction Paths ◽  
Chemical Methods ◽  
Quantum Chemical Methods ◽  
Co Dissociation ◽  
Catalytically Active ◽  
Catalytic Reactivity

State of the art computational quantum-chemical methods enable the modelling of catalytically active sites with an accuracy of relevance to chemical predictability. This opens the possibility to predict reaction paths of elementary reaction steps on catalytically active surfaces. The results of such an approach are illustrated for a few dissociation and association reactions as they occur on transition metal surfaces. Examples to be given concern CO dissociation, carbon-carbon coupling and NH 3 oxidation. Reaction paths appear to be controlled by the principle of minimum surface atom sharing.

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