A unique proton coupled electron transfer pathway for electrochemical reduction of acetophenone in the ionic liquid [BMIM][BF4] under a carbon dioxide atmosphere

2011 ◽  
Vol 13 (12) ◽  
pp. 3461 ◽  
Author(s):  
Shu-Feng Zhao ◽  
La-Xia Wu ◽  
Huan Wang ◽  
Jia-Xing Lu ◽  
Alan M. Bond ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Electron Transfer ◽  
Ionic Liquid ◽  
Electrochemical Reduction ◽  
Electron Transfer Pathway ◽  
Proton Coupled Electron Transfer ◽  
Carbon Dioxide Atmosphere

The water–boryl radical as a proton-coupled electron transfer reagent for carbon dioxide, formic acid, and formaldehyde — Theoretical approach

2013 ◽  
Vol 91 (2) ◽  
pp. 155-168
Author(s):  
Waled Tantawy ◽  
Ahmed Hashem ◽  
Nabil Yousif ◽  
Eman Flefel
Keyword(s):  
Carbon Dioxide ◽  
Hydrogen Bond ◽  
Electron Transfer ◽  
Hydrogen Atom ◽  
Transfer Process ◽  
Carbonyl Compounds ◽  
Hydrogen Atom Transfer ◽  
Transfer Reactions ◽  
Atom Transfer ◽  
Proton Coupled Electron Transfer

The thermochemistry of the hydrogen atom transfer reactions from the H2O–BX2 radical system (X = H, CH3, NH2, OH, F) to carbon dioxide, formic acid, and (or) formaldehyde, which produce hydroxyformyl, dihydroxymethyl, and hydroxymethyl radicals, respectively, were investigated theoretically at ROMP2/6–311+G(3DF,2P)//UB3LYP/6–31G(D) and UG3(MP2)-RAD levels of theory. Surprisingly, in the cases of a strong Lewis acid (X = H, CH3, F), the spin transfer process from the water–boryl radical to the carbonyl compounds was barrier-free and associated with a dramatic reduction in the B–H bond dissociation energy (BDE) relative to that of isolated water–borane complexes. Examining the coordinates of these reactions revealed that the entire hydrogen atom transfer process is governed by the proton-coupled electron transfer (PCET) mechanism. Hence, the elucidated mechanism has been applied in the cases of weak Lewis acids (X = NH2, OH), and the variation in the accompanied activation energy was attributed to the stereoelectronic effect interplaying in CO2 and HCOOH compared with HCHO. We ascribed the overall mechanism as a SA-induced five-center cyclic PCET, in which the proton transfers across the so-called complexation-induced hydrogen bond (CIHB) channel, while the SOMOB–LUMOC=O′ interaction is responsible for the electron migration process. Owing to previous reports that interrelate the hydrogen-bonding and the rate of proton-coupled electron-transfer reactions, we postulated that “the rate of the PCET reaction is expected to be promoted by the covalency of the hydrogen bond, and any factor that enhances this covalency could be considered an activator of the PCET process.” This postulate could be considered a good rationale for the lack of a barrier associated with the hydrogen atom transfer from the water-boryl radical system to the carbonyl compounds. Light has been shed on the water–boryl radical reagent from the thermodynamic perspective.

The award of medals by the President, Sir George Porter, at the Anniversary Meeting, 30 November 1987

1988 ◽  
Vol 417 (1852) ◽  
pp. 1-5
Keyword(s):  
Carbon Dioxide ◽  
Electron Transfer ◽  
Chemical Analysis ◽  
Water Oxidation ◽  
Carbon Dioxide Reduction ◽  
Electron Transfer Pathway ◽  
Starting Point ◽  
Main Pathway ◽  
Isolated Chloroplasts ◽  
Detailed Chemical

The Copley Medal is awarded to Dr R. Hill, F. R. S., in recognition of his pioneering contributions to the understanding of the nature and mechanism of the main pathway of electron transport in photosynthesis. Almost fifty years ago Hill made the first important discovery that allowed detailed chemical analysis of the pathways of photosynthesis, when he demon­strated the light-driven oxidation of water by isolated chloroplasts, and this made it possible to study water oxidation separately from carbon-dioxide reduction. This was the starting point in the elucidation of the electron-transfer pathway in photosynthesis, and in 1951 Hill, with R. Scarisbrick, uncovered the first com­ponent in the chain when they discovered cytochrome and established its key properties. Subsequently, with H. E. Davenport, Hill discovered the second com­ponent of the chain, shown later by others to be ferredoxin. With F. Bendall he formulated the ‘Z-scheme’ to describe the mechanism of electron transfer in photosynthesis in chloroplasts, which showed the relation between the photochemically driven elements and conventional electron-transfer chains found in other biological systems. This proposal brought great clarity to the field and set the scene for further detailed elucidation of the mechanisms.

Electrochemical reduction of aromatic ketones in 1-butyl-3-methylimidazolium-based ionic liquids in the presence of carbon dioxide: the influence of the ketone substituent and the ionic liquid anion on bulk electrolysis product distribution

2015 ◽  
Vol 17 (29) ◽  
pp. 19247-19254 ◽  
Author(s):  
Shu-Feng Zhao ◽  
Mike Horne ◽  
Alan M. Bond ◽  
Jie Zhang
Keyword(s):  
Carbon Dioxide ◽  
Ionic Liquid ◽  
Ionic Liquids ◽  
Electrochemical Reduction ◽  
Product Distribution ◽  
Aromatic Ketone ◽  
Aromatic Ketones ◽  
Bulk Electrolysis ◽  
Electrolysis Product

The yield of electrocarboxylation of aromatic ketone depends on the imidazolium-based ionic liquid anion and the ketone substituent.

scholarly journals Mechanism of Aqueous Carbon Dioxide Reduction by the Solvated Electron

2020 ◽  
Author(s):  
Vladimir Rybkin
Keyword(s):  
Carbon Dioxide ◽  
Electron Transfer ◽  
Plasma Chemistry ◽  
Reorganization Energy ◽  
Carbon Dioxide Reduction ◽  
Solvated Electron ◽  
Intermediate Transformation ◽  
Proton Coupled Electron Transfer ◽  
Key Species ◽  
Proton Migration

Aqueous solvated electron, e<sub>aq</sub>, a key species in radiation and plasma chemistry, can effciently reduce CO<sub>2</sub> in a potential green chemistry application. Here, the mechanism of this reaction is unravelled by condensed-phase Born-Oppenheimer molecular dynamics based on the correlated wave function and accurate DFT approximation. We introduce and apply the holistic protocol for solvated electron's reactions encompassing all relevant reaction stages starting from diffusion. The carbon dioxide reduction proceeds via a cavity intermediate, which is separated from the product, CO2<sup>-</sup>, by an energy barrier due to the bending of CO<sub>2</sub> and the corresponding solvent reorganization energy. The formation of the intermediate is caused by solvated electron's diffusion, whereas the intermediate transformation to CO<sub>2</sub><sup>-</sup> is triggered by solvent fluctuations. This picture of activation-controlled e<sub>aq</sub> reaction is very different from both rapid barrierless electron transfer, and proton-coupled electron transfer, where key transformations are caused by proton migration.

Mechanistic insights into carbon dioxide utilization by superoxide ion generated electrochemically in ionic liquid electrolyte

2021 ◽  
Author(s):  
Ahmed Halilu ◽  
Maan Hayyan ◽  
Mohamed Kheireddine Aroua ◽  
Rozita Yusoff ◽  
Hanee F. Hizaddin
Keyword(s):  
Carbon Dioxide ◽  
Ionic Liquid ◽  
Reaction Mechanism ◽  
Electrochemical Reduction ◽  
Sustainable Use ◽  
Liquid Electrolyte ◽  
Superoxide Ion ◽  
Ionic Liquid Electrolyte ◽  
Carbon Dioxide Utilization ◽  
The One

Understanding the reaction mechanism that controls the one-electron electrochemical reduction of oxygen is essential for sustainable use of the superoxide ion (O2˙−) for CO2 conversion.

Electrochemical Reduction of Aqueous Imidazolium on Pt(111) by Proton Coupled Electron Transfer

2014 ◽  
Vol 58 (1) ◽  
pp. 23-29 ◽  
Author(s):  
Kuo Liao ◽  
Mikhail Askerka ◽  
Elizabeth L. Zeitler ◽  
Andrew B. Bocarsly ◽  
Victor S. Batista
Keyword(s):  
Electron Transfer ◽  
Electrochemical Reduction ◽  
Proton Coupled Electron Transfer
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