Isotopic 18O/16O substitution study on the direct partial oxidation of CH4 to dimethyl ether over a Pt/Y2O3 catalyst using NO/O2 as an oxidant

2021 ◽  
Vol 11 (8) ◽  
pp. 2708-2712
Author(s):  
I. Tyrone Ghampson ◽  
Sean-Thomas B. Lundin ◽  
Tetsuya Shishido ◽  
S. Ted Oyama
Keyword(s):  
Isotope Effect ◽  
Dimethyl Ether ◽  
Partial Oxidation ◽  
Kinetic Isotope Effect ◽  
Kinetic Isotope ◽  
Direct Partial Oxidation

Dimethyl ether (DME) is produced by partial oxidation of CH4 with NO/O2 on Pt/Y2O3. Isotopic oxygen (18O2) is used to confirm molecular O2 as the ultimate oxidant and a kinetic isotope effect for 18O/16O is observed.

Reaction of Dimethyl Ether with Hydroxyl Radicals: Kinetic Isotope Effect and Prereactive Complex Formation

2013 ◽  
Vol 117 (35) ◽  
pp. 8343-8351 ◽  
Author(s):  
Cornelie Bänsch ◽  
Johannes Kiecherer ◽  
Milan Szöri ◽  
Matthias Olzmann
Keyword(s):  
Complex Formation ◽  
Isotope Effect ◽  
Dimethyl Ether ◽  
Hydroxyl Radicals ◽  
Kinetic Isotope Effect ◽  
Kinetic Isotope

Quantum electrocatalysts: theoretical picture, electrochemical kinetic isotope effect analysis, and conjecture to understand microscopic mechanisms

2020 ◽  
Vol 22 (20) ◽  
pp. 11219-11243 ◽  
Author(s):  
Ken Sakaushi
Keyword(s):  
Isotope Effect ◽  
Kinetic Isotope Effect ◽  
Effect Analysis ◽  
Kinetic Isotope

The fundamental aspects of quantum electrocatalysts are discussed together with the newly developed electrochemical kinetic isotope effect (EC-KIE) approach.

scholarly journals l-mandelate dehydrogenase from Rhodotorula graminis: comparisons with the l-lactate dehydrogenase (flavocytochrome b2) from Saccharomyces cerevisiae

1993 ◽  
Vol 290 (1) ◽  
pp. 103-107 ◽  
Author(s):  
O Smékal ◽  
M Yasin ◽  
C A Fewson ◽  
G A Reid ◽  
S K Chapman
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Lactate Dehydrogenase ◽  
Isotope Effect ◽  
Kinetic Isotope Effect ◽  
Dimensional Structure ◽  
Striking Difference ◽  
Kinetic Properties ◽  
Proton Abstraction ◽  
Rate Determining Step ◽  
Kinetic Isotope

L-Lactate dehydrogenase (L-LDH) from Saccharomyces cerevisiae and L-mandelate dehydrogenase (L-MDH) from Rhodotorula graminis are both flavocytochromes b2. The kinetic properties of these enzymes have been compared using steady-state kinetic methods. The most striking difference between the two enzymes is found by comparing their substrate specificities. L-LDH and L-MDH have mutually exclusive primary substrates, i.e. the substrate for one enzyme is a potent competitive inhibitor for the other. Molecular-modelling studies on the known three-dimensional structure of S. cerevisiae L-LDH suggest that this enzyme is unable to catalyse the oxidation of L-mandelate because productive binding is impeded by steric interference, particularly between the side chain of Leu-230 and the phenyl ring of mandelate. Another major difference between L-LDH and L-MDH lies in the rate-determining step. For S. cerevisiae L-LDH, the major rate-determining step is proton abstraction at C-2 of lactate, as previously shown by the 2H kinetic-isotope effect. However, in R. graminis L-MDH the kinetic-isotope effect seen with DL-[2-2H]mandelate is only 1.1 +/- 0.1, clearly showing that proton abstraction at C-2 of mandelate is not rate-limiting. The fact that the rate-determining step is different indicates that the transition states in each of these enzymes must also be different.

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