Mechanism of the Hydrogen Transfer from the OH Group to Oxygen‐Centered Radicals: Proton‐Coupled Electron‐Transfer versus Radical Hydrogen Abstraction

Olivella, Santiago; Anglada, Josep M.; Solé, Albert; Bofill, Josep María

doi:10.1002/chem.200305714

Cited by 65 publications

(105 citation statements)

References 77 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[29] This fact was later explained because the acidic hydrogen is abstracted through a proton-coupled electron transfer mechanism. [30,31] The complete details of the reaction mechanism of reactions 1-3 are given elsewhere [30] and Scheme 1 shows their pictorial representation. Reaction (1) can occur in two different ways, namely through a proton-coupled electron transfer mechanism (pcet, Scheme 1 a) or through a hydrogen atom transfer process (hat, Scheme 1 b).…”

mentioning

confidence: 99%

Different Catalytic Effects of a Single Water Molecule: The Gas‐Phase Reaction of Formic Acid with Hydroxyl Radical in Water Vapor

Anglada

González

2009

ChemPhysChem

Self Cite

View full text Add to dashboard Cite

The effect of a single water molecule on the reaction mechanism of the gas-phase reaction between formic acid and the hydroxyl radical was investigated with high-level quantum mechanical calculations using DFT-B3LYP, MP2 and CCSD(T) theoretical approaches in concert with the 6-311+G(2df,2p) and aug-cc-pVTZ basis sets. The reaction between HCOOH and HO has a very complex mechanism involving a proton-coupled electron transfer process (pcet), two hydrogen-atom transfer reactions (hat) and a double proton transfer process (dpt). The hydroxyl radical predominantly abstracts the acidic hydrogen of formic acid through a pcet mechanism. A single water molecule affects each one of these reaction mechanisms in different ways, depending on the way the water interacts. Very interesting is also the fact that our calculations predict that the participation of a single water molecule results in the abstraction of the formyl hydrogen of formic acid through a hydrogen atom transfer process (hat).

show abstract

mentioning

confidence: 99%

Different Catalytic Effects of a Single Water Molecule: The Gas‐Phase Reaction of Formic Acid with Hydroxyl Radical in Water Vapor

Anglada

González

2009

ChemPhysChem

Self Cite

View full text Add to dashboard Cite

show abstract

“…This interpretation of the HOMO and HOMO-1 was consistent with the PCET picture, except they are fully occupied, which is indicative of the protons and electrons transferred to different acceptor (CO 2 ) sites. [63][64][65] Analysis of the spin density, visualized in Fig. 4, demonstrated that it was concentrated at first on the boron atom (Fig.…”

Section: Resultsmentioning

confidence: 99%

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

et al. 2013

View full text Add to dashboard Cite

The thermochemistry of the hydrogen atom transfer reactions from the H 2 O-BX 2 radical system (X = H, CH 3 , NH 2 , 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, CH 3 , 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 = NH 2 , OH), and the variation in the accompanied activation energy was attributed to the stereoelectronic effect interplaying in CO 2 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 complexationinduced hydrogen bond (CIHB) channel, while the SOMO B -LUMO C=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.Key words: -boryl radical, complexation-induced hydrogen bond (CIHB), proton-coupled electron transfer (PCET), B-H bond dissociation energies (BDEs).Résumé : Faisant appel à des calculs théoriques effectués aux niveaux ROMP2/6-311+G(3DF,2P)//UB3LYP/6-31G(D) et UG3(MP2)-RAD de la théorie, on a effectué une étude de la thermochimie des réactions de transfert d'atomes d'hydrogène de systèmes radicalaires H 2 O-BX 2 vers le dioxyde de carbone, l'acide formique et (ou) le formaldéhyde qui conduisent respectivement à la formation de radicaux hydroxyformyle, dihydroxyméthyle et hydroxyméthyle. D'une façon surprenant, dans les cas d'acides de Lewis forts (X = H, CH 3 , F) les processus de transferts de spin des radicaux eau-boryle vers les composés carbonylés ne comportent aucune barrière et ils sont associés à une réduction dramatique de l'énergie de la dissociation de la liaison (EDL) B-H relative à celle des complexes eau-boranes isolés. L'examen des coordonnées de la réaction de ces réactions révèle que, le processus de transfert de l'atome d'hydrogène est gouverné par le mé...

show abstract

“…The above results revealed that there were some other factors influencing the reaction besides the redox potential of quinone. The process of electron transfer between p-BQ and NHPI should be a proton-coupled electron transfer (PCET) process because the energy of the transition structure of PCET is lower than that of the conventional radical hydrogen atom abstraction mechanism [15][16][17]. In this pathway, NHPI interacted with quinone to give a hydrogen-bond complex, and then electron proton transfer occurred.…”

Section: Catalytic Activity Of Substituted Benzoquinone In Ethylbenzementioning

confidence: 98%

Electronic Effect of Substituent of Quinones on their Catalytic Performance in Hydrocarbons Oxidation

et al. 2008

View full text Add to dashboard Cite

Quinones with electron-withdrawing F, Cl or Br groups and N-hydroxyphthalimide (NHPI) were used as catalysts in selective oxidation of hydrocarbons with molecular oxygen as oxidant. The catalytic activity in the selective oxidation of ethylbenzene to oxygenation products was in the following order: p-benzoquinone\tetrafluoro-pbenzoquinone & tetrachloro-p-benzoquinone\tetrabromo-p-benzoquinone (p-TBBQ). Moderate electron-withdrawing power of substituent was suitable for quinone abstracting hydrogen from NHPI to generate reactive phthalimido-Noxyl (PINO). The catalytic activity of p-TBBQ/NHPI, the best catalyst in our study, was also tested in the selective oxidation of alkylarenes, alkenes and alkanes.

show abstract

Mechanism of the Hydrogen Transfer from the OH Group to Oxygen‐Centered Radicals: Proton‐Coupled Electron‐Transfer versus Radical Hydrogen Abstraction

Cited by 65 publications

References 77 publications

Different Catalytic Effects of a Single Water Molecule: The Gas‐Phase Reaction of Formic Acid with Hydroxyl Radical in Water Vapor

Different Catalytic Effects of a Single Water Molecule: The Gas‐Phase Reaction of Formic Acid with Hydroxyl Radical in Water Vapor

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

Electronic Effect of Substituent of Quinones on their Catalytic Performance in Hydrocarbons Oxidation

Contact Info

Product

Resources

About