Dynamically Bifurcating Hydride Transfer Mechanism and Origin of Inverse Isotope Effect for Heterodinuclear AgRu-Catalyzed Alkyne Semihydrogenation

ACS Catalysis ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 2657-2663 ◽  
Author(s):  
Ying Zhang ◽  
Malkanthi K. Karunananda ◽  
Hsien-Cheng Yu ◽  
Kyle J. Clark ◽  
Wendy Williams ◽  
...  
Keyword(s):  
Isotope Effect ◽  
Hydride Transfer ◽  
Transfer Mechanism ◽  
Inverse Isotope Effect

scholarly journals Nitrogen isotope effects can be used to diagnose N transformations in wastewater anammox systems

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Paul M. Magyar ◽  
Damian Hausherr ◽  
Robert Niederdorfer ◽  
Nicolas Stöcklin ◽  
Jing Wei ◽  
...  
Keyword(s):  
Isotope Effect ◽  
Isotope Composition ◽  
Isotope Effects ◽  
Nitrogen Isotope ◽  
Anammox Bacteria ◽  
Ammonium Oxidation ◽  
Experimental Conditions ◽  
N Transformations ◽  
Natural Systems ◽  
Inverse Isotope Effect

AbstractAnaerobic ammonium oxidation (anammox) plays an important role in aquatic systems as a sink of bioavailable nitrogen (N), and in engineered processes by removing ammonium from wastewater. The isotope effects anammox imparts in the N isotope signatures (15N/14N) of ammonium, nitrite, and nitrate can be used to estimate its role in environmental settings, to describe physiological and ecological variations in the anammox process, and possibly to optimize anammox-based wastewater treatment. We measured the stable N-isotope composition of ammonium, nitrite, and nitrate in wastewater cultivations of anammox bacteria. We find that the N isotope enrichment factor 15ε for the reduction of nitrite to N2 is consistent across all experimental conditions (13.5‰ ± 3.7‰), suggesting it reflects the composition of the anammox bacteria community. Values of 15ε for the oxidation of nitrite to nitrate (inverse isotope effect, − 16 to − 43‰) and for the reduction of ammonium to N2 (normal isotope effect, 19–32‰) are more variable, and likely controlled by experimental conditions. We argue that the variations in the isotope effects can be tied to the metabolism and physiology of anammox bacteria, and that the broad range of isotope effects observed for anammox introduces complications for analyzing N-isotope mass balances in natural systems.

Ruthenium catalysed oxidation of cyclohexanol

1982 ◽  
Vol 35 (6) ◽  
pp. 1245 ◽  
Author(s):  
P Becker ◽  
JK Beattie
Keyword(s):  
Aqueous Solution ◽  
Isotope Effect ◽  
Phosphate Buffer ◽  
Hydride Transfer ◽  
Deuterium Isotope Effect ◽  
Rate Law ◽  
Alkaline Aqueous Solution ◽  
Catalysed Oxidation

The oxidation of cyclohexanol by ferricyanide in alkaline aqueous solution is catalysed by micromolar concentrations of K3RuCl6. The rate law at 25.0�C in pH 11.9 phosphate buffer containing 0.50 M NaCl is -d[FeIII]/dt = [Ru](2klk2[alcohol][FeIII])/(2kl[alcohol] + k2[FeIII]) with kl 12 � 2 mol-1 1. s-1 and k2 (2.5 � 0.2) × 102 mol-1 1. s-1. A deuterium isotope effect of about 4 is observed when (D12)cyclohexanol is used. A mechanism consistent with these observations involves reduction of the RuIII catalyst by hydride transfer from the alcohol followed by reoxidation by ferricyanide to the original RulIII state.

scholarly journals Empirical Valence Bond Simulations Suggest a Direct Hydride Transfer Mechanism for Human Diamine Oxidase

ACS Omega ◽  
2018 ◽  
Vol 3 (4) ◽  
pp. 3665-3674 ◽  
Author(s):  
Aleksandra Maršavelski ◽  
Dušan Petrović ◽  
Paul Bauer ◽  
Robert Vianello ◽  
Shina Caroline Lynn Kamerlin
Keyword(s):  
Diamine Oxidase ◽  
Valence Bond ◽  
Hydride Transfer ◽  
Transfer Mechanism ◽  
Empirical Valence Bond ◽  
Human Diamine Oxidase

Mechanistic insights and computational design of half-sandwich iridium and rhodium complexes for hydrogenation of quinoline

2019 ◽  
Vol 43 (22) ◽  
pp. 8459-8464
Author(s):  
Xiuli Yan ◽  
Xinzheng Yang
Keyword(s):  
Dft Calculations ◽  
Hydride Transfer ◽  
Computational Design ◽  
Transfer Mechanism ◽  
Rhodium Complexes ◽  
Half Sandwich

DFT calculations reveal a stepwise proton and hydride transfer mechanism for the hydrogenation of quinoline to 1,2,3,4-tetrahydroquinoline catalysed by half-sandwich Cp*Ir(NHC) complexes.

Evidence Against a Hydrogen Abstraction Mechanism in the Photorearrangement of Azoxybenzene to 2-Hydroxyazobenzene

1973 ◽  
Vol 51 (23) ◽  
pp. 3827-3841 ◽  
Author(s):  
David J. W. Goon ◽  
N. G. Murray ◽  
Jean-Pierre Schoch ◽  
N. J. Bunce
Keyword(s):  
Free Radical ◽  
Quantum Yield ◽  
Isotope Effect ◽  
Polar Solvent ◽  
Hydrogen Abstraction ◽  
Fold Increase ◽  
Transfer Mechanism ◽  
Deuterium Isotope Effect ◽  
Ring Carbon

In an attempt to distinguish between ionic and free radical mechanisms for the photorearrangement of azoxybenzene to 2-hydroxyazobenzene, aromatic azoxycompounds carrying C—H functions ortho to the azoxy linkage have been prepared and irradiated. The failure of these weaker C—H bonds to divert the reaction from its normal course argues against a hydrogen abstraction–hydroxyl transfer mechanism. This conclusion is supported by the observation of a 30-fold increase in quantum yield for 2-hydroxyazobenzene formation on changing from a non-polar to a polar solvent and by the kinetic deuterium isotope effect, which is too small for the primary isotope effect required by the abstraction mechanism. It is concluded that the experimental observations to date may most easily be accommodated in the route originally proposed by Badger and Buttery, where the rearrangement is seen as a substitution by oxygen at the ortho ring carbon.

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