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Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation

Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation

Introduction
Like alkenes, alkynes can be reduced to alkanes in the presence of transition metal catalysts such as Pt, Pd, or Ni. The reaction involves two sequential syn additions of hydrogen via a cis-alkene intermediate.

Electron Behavior

Electron Behavior

Overview
Electrons are negatively charged subatomic particles that are attracted to an orbit around the positively-charged nucleus of an atom. They reside in locations that are associated with energy levels called shells and are further organized into sub-shells and orbitals within each shell.
Electrons Orbit the Nucleus
Electrons are found in specific locations outside of the nucleus. The shell in which an electron resides indicates the general energy level of the electron: those closer to the...

Reduction of Alkenes: Catalytic Hydrogenation

Reduction of Alkenes: Catalytic Hydrogenation

Alkenes undergo reduction by the addition of molecular hydrogen to give alkanes. Because the process generally occurs in the presence of a transition-metal catalyst, the reaction is called catalytic hydrogenation.
Metals like palladium, platinum, and nickel are commonly used in their solid forms — fine powder on an inert surface. As these catalysts remain insoluble in the reaction mixture, they are referred to as heterogeneous catalysts.
The hydrogenation process takes place on the...

Reduction of Alkenes: Asymmetric Catalytic Hydrogenation

Reduction of Alkenes: Asymmetric Catalytic Hydrogenation

Catalytic hydrogenation of alkenes is a transition-metal catalyzed reduction of the double bond using molecular hydrogen to give alkanes. The mode of hydrogen addition follows syn stereochemistry.
The metal catalyst used can be either heterogeneous or homogeneous. When hydrogenation of an alkene generates a chiral center, a pair of enantiomeric products is expected to form. However, an enantiomeric excess of one of the products can be facilitated using an enantioselective reaction or an...

Reduction of Benzene to Cyclohexane: Catalytic Hydrogenation

Reduction of Benzene to Cyclohexane: Catalytic Hydrogenation

Unlike the easy catalytic hydrogenation of an alkene double bond, hydrogenation of a benzene double bond under similar reaction conditions does not take place easily. For example, in the reduction of stilbene, the benzene ring remains unaffected while the alkene bond gets reduced. Hydrogenation of an alkene double bond is exothermic and a favorable process. In contrast, to hydrogenate the first unsaturated bond of benzene, an energy input is needed; that is, the process is endothermic. This is...

Radical Formation: Homolysis

Radical 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.

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Updated: Nov 4, 2025

Single-Molecule Förster Resonance Energy Transfer Methods for Real-Time Investigation of the Holliday Junction Resolution by GEN1

Single-Molecule Förster Resonance Energy Transfer Methods for Real-Time Investigation of the Holliday Junction Resolution by GEN1

Published on: September 18, 2019

Electron-Catalyzed Dehydrogenation in a Single-Molecule Junction.

Hongliang Chen^1,2,3, Feng Jiang⁴, Chen Hu⁵

¹Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States.

Journal of the American Chemical Society

|May 27, 2021

Summary

This summary is machine-generated.

Electrons can unexpectedly trigger chemical reactions in single molecules, altering their electrical properties. This study reveals electron catalysis drives ethane-to-ethene transformation in molecular junctions, impacting conductance measurements.

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Single-Molecule Förster Resonance Energy Transfer Methods for Real-Time Investigation of the Holliday Junction Resolution by GEN1

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Published on: April 16, 2018

Area of Science:

Molecular electronics
Surface science
Catalysis

Background:

Electron transport through single molecules is a key area in molecular electronics.
Electrons can act as catalysts for radical reactions, a factor often overlooked in conductance studies.
Unexpected electron-mediated reactions can influence measurements in single-molecule junctions.

Purpose of the Study:

To investigate counterintuitive structure-property relationships in molecular conductance.
To demonstrate and understand electron catalysis in single-molecule junctions.
To explore the mechanism of electron-catalyzed ethane-to-ethene transformation.

Main Methods:

Fabrication and characterization of single-molecule junctions.
Electrochemical ensemble experiments.
Theoretical calculations (e.g., density functional theory).

Main Results:

Molecules with saturated bipyridinium-ethane backbones showed similar conductance to those with conjugated bipyridinium-ethene backbones.
An ethane-to-ethene transformation was observed in the single-molecule junction.
Electrons were found to trigger the redox process, and the electric field promoted dehydrogenation.

Conclusions:

Electron catalysis plays a critical role in interpreting single-molecule conductance data.
An ethane-to-ethene transformation occurs via electron-catalyzed dehydrogenation within the junction.
This work provides insights into electrocatalytic hydrogen production mechanisms at the single-molecule level.