Synthesis, structure, and exchange reactions of rhenium alkoxide and aryloxide complexes. Evidence for both proton and hydrogen atom transfer in the exchange transition state

1993 ◽  
Vol 12 (3) ◽  
pp. 781-796 ◽  
Author(s):  
Robert D. Simpson ◽  
Robert G. Bergman
Keyword(s):  
Hydrogen Atom ◽  
Transition State ◽  
Hydrogen Atom Transfer ◽  
Atom Transfer ◽  
Exchange Reactions

scholarly journals Anchimeric Assistance in Hydrogen-Atom Transfer to Bromine

2004 ◽  
Vol 57 (7) ◽  
pp. 651 ◽  
Author(s):  
Anna K. Croft ◽  
Christopher J. Easton
Keyword(s):  
Free Radical ◽  
Hydrogen Atom ◽  
Transition State ◽  
Hydrogen Atom Transfer ◽  
Atom Transfer ◽  
Rate Enhancement ◽  
Anchimeric Assistance ◽  
Electron Donation ◽  
Electron Demand

The free-radical benzylic brominations of series of phenylalanine derivatives and O-phenylalkyl benzoates and N-phenylalkylamides with N-bromosuccinimide exhibit anchimeric assistance by neighbouring ester and amido groups. Rate enhancement occurs through electron donation to the electropositive carbon centre that develops in the transition state of the hydrogen-atom transfer to bromine. The extent of the effect depends on the electron demand at the benzylic position and the electron-donating ability of the neighbouring group.

On the Role of Hydrogen Atom Transfer (HAT) in Thermal Activation of Methane by MnO+: Entropy vs. Energy

2019 ◽  
Vol 233 (6) ◽  
pp. 771-783 ◽  
Author(s):  
Brendan C. Sweeny ◽  
Hanqing Pan ◽  
Shaun G. Ard ◽  
Nicholas S. Shuman ◽  
Albert A. Viggiano
Keyword(s):  
Hydrogen Atom ◽  
Transition State ◽  
Branching Fractions ◽  
Hydrogen Atom Transfer ◽  
Atom Transfer ◽  
Temperature Dependent ◽  
Proton Coupled Electron Transfer ◽  
Selected Ion Flow Tube ◽  
Increasing Temperature

Abstract The temperature dependent kinetics and product branching fractions of first-row transition metal oxide cation MnO+ with CH4 and CD4 at temperatures between 200 and 600 K are measured using a selected-ion flow tube apparatus. Likely reaction mechanisms are determined by comparison of temperature dependent kinetics to statistical modeling along calculated reaction coordinates. The data is well-modeled with the reaction proceeding over a rate limiting four-centered transition state leading to an insertion intermediate, similar to reactions of NiO+ and FeO+, and showing characteristics of proton-coupled electron transfer (PCET). However, a more direct pathway traversing a transition state of hydrogen atom transfer (HAT) character to a hydroxyl intermediate is found to possibly be competitive, especially with increasing temperature. While uncertainties in calculated energetics limit quantitative assessment of the role of HAT at thermal energies, it is clear that this mechanism becomes increasingly prevalent in higher energy regimes.

scholarly journals Nitroxyl Radical Plus Hydroxylamine Pseudo Self-Exchange Reactions: Tunneling in Hydrogen Atom Transfer

2009 ◽  
Vol 131 (33) ◽  
pp. 11985-11997 ◽  
Author(s):  
Adam Wu ◽  
Elizabeth A. Mader ◽  
Ayan Datta ◽  
David A. Hrovat ◽  
Weston Thatcher Borden ◽  
...  
Keyword(s):  
Hydrogen Atom ◽  
Nitroxyl Radical ◽  
Hydrogen Atom Transfer ◽  
Atom Transfer ◽  
Exchange Reactions
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