Related Experiment Video
Updated: Sep 20, 2025

Photogeneration of N-Heterocyclic Carbenes: Application in Photoinduced Ring-Opening Metathesis Polymerization
Published on: November 29, 2018
Photochemically Induced 1,3-Butadiene Ring-Closure from the Topological Analysis of the Electron Localization
Cristian Guerra1,2, Leandro Ayarde-Henríquez1, Mario Duque-Noreña1
1Universidad Andrés Bello, Facultad de Ciencias Exactas, Departamento de Ciencias Químicas. Avenida, República 275, 8370146, Santiago de Chile, Chile.
Abstract:
The electronic rearrangement featuring the photochemically-induced 1,3-cis-butadiene is discussed within a bonding evolution theory (BET) perspective based on the topological analysis of the electron localization function and Thom's catastrophe theory. The process involves the vertical singlet-singlet excitation S0 →S2 , and the subsequent deactivation implying the S2 /S1 and S1 /S0 conical intersection regions. BET results reveal that the new CC bond is finally formed on the S0 surface, as also recently found in the photochemical addition of two ethylenes [Phys. Chem. Chem. Phys. 23, 20598, (2021)].
Related Concept Videos
π Molecular Orbitals of 1,3-Butadiene
The simplest conjugated diene is 1,3-butadiene: a four-carbon system where each carbon is sp2-hybridized and has an unhybridized p orbital that contains an unpaired electron. According to molecular orbital theory, atomic orbitals combine to form molecular orbitals such that the number...
Photochemical Electrocyclic Reactions: Stereochemistry
Selection Rules: Photochemical Activation
Electrophilic 1,2- and 1,4-Addition of X2 to 1,3-Butadiene
Thermal and Photochemical Electrocyclic Reactions: Overview
Thermal Electrocyclic Reactions: Stereochemistry
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.
Electrophilic 1,2- and 1,4-Addition of HX to 1,3-Butadiene

