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Thermal and Photochemical Electrocyclic Reactions: Overview

Thermal and Photochemical Electrocyclic Reactions: Overview

Electrocyclic reactions are reversible reactions. They involve an intramolecular cyclization or ring-opening of a conjugated polyene. Shown below are two examples of electrocyclic reactions. In the first reaction, the formation of the cyclic product is favored. In contrast, in the second reaction, ring-opening is favored due to the high ring strain associated with cyclobutene formation.

Thermal Electrocyclic Reactions: Stereochemistry

Thermal Electrocyclic Reactions: Stereochemistry

The stereochemistry of electrocyclic reactions is strongly influenced by the orbital symmetry of the polyene HOMO. Under thermal conditions, the reaction proceeds via the ground-state HOMO.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.

Photochemical Electrocyclic Reactions: Stereochemistry

Photochemical Electrocyclic Reactions: Stereochemistry

The absorption of UV–visible light by conjugated systems causes the promotion of an electron from the ground state to the excited state. Consequently, photochemical electrocyclic reactions proceed via the excited-state HOMO rather than the ground-state HOMO. Since the ground- and excited-state HOMOs have different symmetries, the stereochemical outcome of electrocyclic reactions depends on the mode of activation; i.e., thermal or photochemical.
Selection Rules: Photochemical Activation

Electrochemistry: Overview

Electrochemistry: Overview

Electrochemistry is the branch of chemistry that studies the relationship between electrical quantities and chemical reactions, particularly oxidation and reduction. Oxidation is the loss of electrons from a substance, whereas reduction refers to the gain of electrons. A substance with a strong electron affinity is called an oxidizing agent (oxidant), and a reducing agent (reductant) is a species that donates electrons. Oxidation and reduction processes are pivotal to electrochemical reactions,...

Reduction of Alkenes: Asymmetric Catalytic Hydrogenation

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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...

Catalysis

Catalysis

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.

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Updated: Nov 3, 2025

Synthesis and Performance Characterizations of Transition Metal Single Atom Catalyst for Electrochemical CO2 Reduction

Synthesis and Performance Characterizations of Transition Metal Single Atom Catalyst for Electrochemical CO2 Reduction

Published on: April 10, 2018

Electrocatalysis as an enabling technology for organic synthesis.

Luiz F T Novaes¹, Jinjian Liu, Yifan Shen

¹Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA. songlin@cornell.edu.

Chemical Society Reviews

|June 1, 2021

Summary

Synthetic electrocatalysis utilizes electrochemistry to enable challenging organic synthesis reactions. Recent advances focus on redox-active electrocatalysts and mediators for controlled, mild transformations, overcoming conventional limitations.

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Synthesis and Performance Characterizations of Transition Metal Single Atom Catalyst for Electrochemical CO2 Reduction

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Using Cyclic Voltammetry, UV-Vis-NIR, and EPR Spectroelectrochemistry to Analyze Organic Compounds

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Light-driven Enzymatic Decarboxylation

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Area of Science:

Organic Chemistry
Electrochemistry
Catalysis

Background:

Electrochemistry offers a versatile approach for complex organic synthesis.
It enables controlled generation of reactive intermediates under mild conditions.
Electrosynthesis is increasingly employing redox-active electrocatalysts.

Purpose of the Study:

To review key innovations in synthetic electrocatalysis over the past decade.
To emphasize the mechanisms and catalyst design principles.
To discuss various oxidative and reductive electrocatalytic methodologies.

Main Methods:

Review of recent literature in synthetic electrocatalysis.
Analysis of mechanisms and catalyst design.
Classification of methodologies by transformation type and catalyst nature.

Main Results:

Highlighting advancements in controlled generation of radical and radical ion intermediates.
Showcasing the role of electrocatalytic mediators in overcoming synthetic obstacles.
Presenting a range of oxidative and reductive electrocatalytic methods.

Conclusions:

Synthetic electrocatalysis is a rapidly advancing field with significant potential.
Electrocatalyst design and mechanistic understanding are crucial for developing new methods.
Electrocatalysis provides unique pathways distinct from traditional chemical synthesis.