Related Concept Videos
01:26Photochemical 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
Selection Rules: Photochemical Activation
01:26Thermal 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.
00:57Cationic Chain-Growth Polymerization: Mechanism
The cationic polymerization mechanism consists of three steps: initiation, propagation, and termination. In the initiation step of the polymerization process, the π bond of a monomer gets protonated by the Lewis acid catalyst, which is formed from boron trifluoride and water. The protonation of the π bond generates a carbocation stabilized by the electron‐donating group. In the propagation step, the π bond of the second monomer acts as a nucleophile and attacks the generated carbocation,...
01:04Anionic Chain-Growth Polymerization: Mechanism
The mechanism for anionic chain-growth polymerization involves initiation, propagation, and termination steps. In the initiation step, a nucleophilic anion, such as butyl lithium, initiates the polymerization process by attacking the π bond of the vinylic monomer. As a result, a carbanion, stabilized by the electron‐withdrawing group, is generated. The resulting carbanion acts as a Michael donor in the propagation step and attacks the second vinylic monomer, which acts as a Michael acceptor.
01:17Thermal 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.
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.
01:12Cycloaddition Reactions: MO Requirements for Photochemical Activation
Some cycloaddition reactions are activated by heat, while others are initiated by light. For example, a [2 + 2] cycloaddition between two ethylene molecules occurs only in the presence of light. It is photochemically allowed but thermally forbidden.
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Related Experiment Video
Updated: Jun 11, 2026
10:21
Developing Photosensitizer-Cobaloxime Hybrids for Solar-Driven H2 Production in Aqueous Aerobic Conditions
Published on: October 5, 2019
Photoelectrocatalytic self-cross coupling enabling carbon chain elongation.
Yuye Jiao1, Zhiqiang Hu1, Yurou Song1
1State Key Laboratory of Fine Chemical, Frontiers Science Center for Smart Materials Oriented Chemical Engineering, School of Chemical Engineering, Dalian University of Technology, Dalian, P. R. China.
Nature Communications
|June 9, 2026
Summary
This study introduces a novel photoelectrocatalytic (PEC) system for green carbon chain elongation. The system efficiently upgrades small molecules into valuable long-chain chemicals using solar energy.
Area of Science:
- Green Chemistry
- Catalysis
- Sustainable Chemical Synthesis
Background:
- Conventional long-chain chemical production relies on noble-metal catalysts and harsh conditions.
- There is a need for sustainable and efficient methods for producing long-chain compounds.
Purpose of the Study:
- To develop a green and efficient photoelectrocatalytic (PEC) system for carbon chain elongation.
- To enable radical-mediated self-cross-coupling reactions for upgrading C2 molecules to C3 products.
Main Methods:
- Design and implementation of a photoelectrocatalytic (PEC) system.
- Utilizing radical-mediated self-cross-coupling reactions.
- In situ spectroscopy to analyze reaction intermediates.
Main Results:
- Achieved total selectivity exceeding 50% for C2 to C3 upgrading.
- Demonstrated a high production rate of 159.17 mmol m⁻² h⁻¹.
- Showcased universal chain-elongation capability for diverse C2-C6 polyol substrates.
Conclusions:
- The PEC system offers a sustainable pathway for producing long-chain chemicals.
- Chlorine radicals play a crucial role in enhancing radical generation rates.
- This work presents a solar-driven cross-coupling mechanism for advanced chemical synthesis.