Water-gas shift catalysis: kinetic isotope effect identifies surface formates in rate limiting step for Pt/ceria catalysts

2004 ◽  
Vol 268 (1-2) ◽  
pp. 255-266 ◽  
Author(s):  
G JACOBS
Keyword(s):  
Isotope Effect ◽  
Kinetic Isotope Effect ◽  
Water Gas Shift ◽  
Kinetic Isotope ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Ceria Catalysts ◽  
Water Gas ◽  
Rate Limiting

Low temperature water-gas shift: kinetic isotope effect observed for decomposition of surface formates for Pt/ceria catalysts

2004 ◽  
Vol 269 (1-2) ◽  
pp. 63-73 ◽  
Author(s):  
Gary Jacobs ◽  
Patricia M. Patterson ◽  
Uschi M. Graham ◽  
Dennis E. Sparks ◽  
Burtron H. Davis
Keyword(s):  
Low Temperature ◽  
Isotope Effect ◽  
Kinetic Isotope Effect ◽  
Water Gas Shift ◽  
Kinetic Isotope ◽  
Ceria Catalysts ◽  
Water Gas ◽  
Temperature Water

scholarly journals Path Integral Calculation of the Hydrogen/Deuterium Kinetic Isotope Effect in Monoamine Oxidase A-Catalyzed Decomposition of Benzylamine

Molecules ◽  
2019 ◽  
Vol 24 (23) ◽  
pp. 4359 ◽  
Author(s):  
Mateusz Z. Brela ◽  
Alja Prah ◽  
Marek Boczar ◽  
Jernej Stare ◽  
Janez Mavri
Keyword(s):  
Monoamine Oxidase ◽  
Isotope Effect ◽  
Path Integral ◽  
Kinetic Isotope Effect ◽  
Monoamine Oxidase A ◽  
Kinetic Isotope ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Hydrogen Deuterium ◽  
Rate Limiting

Monoamine oxidase A (MAO A) is a well-known enzyme responsible for the oxidative deamination of several important monoaminergic neurotransmitters. The rate-limiting step of amine decomposition is hydride anion transfer from the substrate α–CH2 group to the N5 atom of the flavin cofactor moiety. In this work, we focus on MAO A-catalyzed benzylamine decomposition in order to elucidate nuclear quantum effects through the calculation of the hydrogen/deuterium (H/D) kinetic isotope effect. The rate-limiting step of the reaction was simulated using a multiscale approach at the empirical valence bond (EVB) level. We applied path integral quantization using the quantum classical path method (QCP) for the substrate benzylamine as well as the MAO cofactor flavin adenine dinucleotide. The calculated H/D kinetic isotope effect of 6.5 ± 1.4 is in reasonable agreement with the available experimental values.

scholarly journals How Do Aromatic Nitro Compounds React with Nucleophiles? Theoretical Description Using Aromaticity, Nucleophilicity and Electrophilicity Indices

Molecules ◽  
2020 ◽  
Vol 25 (20) ◽  
pp. 4819
Author(s):  
Kacper Błaziak ◽  
Witold Danikiewicz ◽  
Mieczysław Mąkosza
Keyword(s):  
Kinetic Isotope Effect ◽  
Theoretical Description ◽  
Reaction Conditions ◽  
Kinetic Isotope ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Leaving Group ◽  
Aromatic Nitro ◽  
Rate Limiting ◽  
Reaction Direction

In this study, we present a complete description of the addition of a model nucleophile to the nitroaromatic ring in positions occupied either by hydrogen (the first step of the SNAr-H reaction) or a leaving group (SNAr-X reaction) using theoretical parameters including aromaticity (HOMA), electrophilicity and nucleophilicity indices. It was shown both experimentally and by our calculations, including kinetic isotope effect modeling, that the addition of a nucleophile to the electron-deficient aromatic ring is the rate limiting step of both SNAr-X and SNAr-H reactions when the fast transformation of σH-adduct into the products is possible due to the specific reaction conditions, so this is the most important step of the entire reaction. The results described in this paper are helpful for better understanding of the subtle factors controlling the reaction direction and rate.

Determination of the Isotope Effect of the Enzymatic Oxidation of (R)Carnitine by Displacement of the Equilibrium via Mass Action

1975 ◽  
Vol 30 (7-8) ◽  
pp. 438-441
Author(s):  
Klaus Brendel ◽  
Rubin Bressler ◽  
Miguel A. Alizade
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Isotope Effect ◽  
Mass Action ◽  
Enzymatic Oxidation ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Different Temperatures ◽  
Acid Hydrochloride ◽  
Rate Limiting

Abstract An isotope effect of the dehydrogenation of (R) Carnitine [(R) 3-hydroxy-4-trimethylamino-butyric acid hydrochloride] catalyzed by (R) carnitine dehydrogenase [(R) carnitine: NAD oxido-reductase E.C. 1.1.1.108] from Pseudomonas aeruginosa was measured at different temperatures. It was found that k1H/k3H does not vary greatly with changes of temperature. The value of 3 for k1H/k3H measured at small initial conversions strongly indicated that the rate limiting step of the oxidation of (R) carnitine is the cleavage of the C-H bond at C3.

Ligand-Accelerated Non-Directed C–H Cyanation of Arenes

2018 ◽  
Author(s):  
Luoyan Liu ◽  
Kap-Sun Yeung ◽  
jin-quan yu
Keyword(s):  
Natural Products ◽  
Bond Cleavage ◽  
Drug Molecules ◽  
Kinetic Isotope ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Broad Scope ◽  
Synthetic Utility ◽  
Rate Limiting

<p>We herein report the first example of a 2-pyridone accelerated non-directed C−H cyanation with an arene as the limiting reagent. This protocol is compatible with a broad scope of arenes, including advanced intermediates, drug molecules, and natural products. A kinetic isotope experiment (k<sub>H</sub>/k<sub>D</sub> = 4.40) indicates that the C–H bond cleavage is the rate-limiting step. Also, the reaction is readily scalable, further showcasing the synthetic utility of this method.<i></i></p>

Isotope effect studies of the decomposition of 2-propanol on hafnium(IV) oxide

1977 ◽  
Vol 55 (1) ◽  
pp. 153-157
Author(s):  
Ian M. Hoodless
Keyword(s):  
Hydrogen Bond ◽  
Isotope Effect ◽  
Catalytic Decomposition ◽  
Hafnium Dioxide ◽  
Small Extent ◽  
Dehydrogenation Reaction ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Major Reaction ◽  
Rate Limiting

The catalytic decomposition of 2-propanol on hafnium dioxide has been investigated over the temperature range 355–397 °C by a micropulse reactor technique. The major reaction is one of dehydration to propene but dehydrogenation also occurs to a small extent. Isotope effect measurements with deuterio-2-propanols indicate that the rate-limiting step in dehydration involves cleavage of the β-carbon-hydrogen while in the dehydrogenation reaction it is cleavage of the α-carbon-hydrogen bond.

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