Related Experiment Video
Updated: May 21, 2026
10:21
Developing Photosensitizer-Cobaloxime Hybrids for Solar-Driven H2 Production in Aqueous Aerobic Conditions
Published on: October 5, 2019
Catalysis in hydrogen-bridged radical cations.
Karl J Jobst1, Moschoula A Trikoupis
1Laboratory Services Branch, Ministry of the Environment, 125 Resources Road, Toronto, ON, Canada, M9P 3V6. karl.jobst@ontario.ca
Summary
Hydrogen-bridged radical cations (HBRCs) are stable ion-molecule intermediates. They facilitate molecular transformations through proton-transport catalysis (PTC), enabling isomerization and dissociation in various chemical reactions.
Area of Science:
- Physical Chemistry
- Chemical Physics
- Ion-Molecule Chemistry
Background:
- Hydrogen-bridged radical cations (HBRCs) are stable ion-molecule complexes.
- They function as key intermediates in ion-molecule reactions, facilitating dissociation and association.
- The H-bridge within HBRCs can induce isomerization of the ionic component via H-transfer.
Purpose of the Study:
- To review recent combined experimental and computational studies on catalysis in HBRCs.
- To explore mechanisms involving proton and H atom transfers in HBRC systems.
- To highlight the role of HBRCs in both bimolecular and unimolecular reactions.
Main Methods:
- Review of combined experimental and computational studies.
- Analysis of proposed mechanisms for proton and H atom transfer.
- Investigation of HBRC formation in unimolecular dissociation pathways.
Main Results:
- HBRCs are crucial intermediates in ion-molecule reactions.
- Proton-transport catalysis (PTC) is a key mechanism for isomerization, exemplified by water-catalyzed methanol radical cation isomerization.
- Mechanisms involving both proton and H atom transfers are proposed for various H-shift isomers.
- PTC is relevant in both bimolecular reactions and the unimolecular chemistry of heteroatom-containing ions.
Conclusions:
- HBRCs play a significant role in chemical transformations.
- Proton-transport catalysis is a versatile mechanism for ion isomerization.
- Recent studies underscore the importance of HBRCs in diverse chemical processes, including unimolecular dissociation.
Related Concept Videos
01:11Radical Reactivity: Overview
Radicals, the highly reactive species, gain stability by undergoing three different reactions. The first reaction involves a radical-radical coupling, in which a radical combines with another radical, forming a spin‐paired molecule. The second reaction is between a radical and a spin‐paired molecule, generating a new radical and a new spin‐paired molecule. The third reaction is radical decomposition in a unimolecular reaction, forming a new radical and a spin‐paired molecule. These three...
01:27Catalysis
Catalysis influences the rate of chemical reactions by providing an alternative reaction pathway with lower activation energy. A catalyst speeds up a reaction, but it is not consumed during the process. The fundamental principle of catalysis is the ability of a catalyst to alter the reaction mechanism, often introducing a more efficient pathway than the uncatalyzed process.In a catalyzed reaction, the catalyst participates directly in the reaction mechanism. It interacts with reactants to form...
02:50Catalysis
The presence of a catalyst affects the rate of a chemical reaction. A catalyst is a substance that can increase the reaction rate without being consumed during the process. A basic comprehension of a catalysts’ role during chemical reactions can be understood from the concept of reaction mechanisms and energy diagrams.
00:54Radical Formation: Homolysis
A bond is formed between two atoms by sharing two electrons. When this bond is broken by supplying sufficient energy, either two electrons can be taken up by one atom forming ions by the cleavage called heterolysis, or the two electrons are shared by two atoms, with one each creating radicals by the cleavage called homolysis.
00:47Radical Formation: Abstraction
The electron of an atom can be abstracted from a compound by a relatively unstable radical to generate a new radical of relatively greater stability. For example, an initiator which forms radicals by homolysis can abstract a suitable species like a hydrogen atom or a halogen atom from a compound to generate a new radical. This ability of radicals to propagate by abstraction is a crucial feature of radical chain reactions.
Even though homolysis produces radicals, it is different from radical...
Even though homolysis produces radicals, it is different from radical...
01:03Radical Formation: Overview
A bond can be broken either by heterolytic bond cleavage to form ions or homolytic bond cleavage to yield radicals. A fishhook arrow is used to represent the motion of a single electron in homolytic bond cleavage. There are two main sources from which radicals can be formed:
Radicals from spin-paired molecules:
Radicals can be obtained from spin-paired molecules either by homolysis or electron transfer. While two radicals are formed in the former, an electron is added in the latter, also known...
Radicals from spin-paired molecules:
Radicals can be obtained from spin-paired molecules either by homolysis or electron transfer. While two radicals are formed in the former, an electron is added in the latter, also known...