Related Experiment Video
Updated: Oct 26, 2025

Novel Techniques for Observing Structural Dynamics of Photoresponsive Liquid Crystals
Published on: May 29, 2018
Femtosecond dynamics and coherence of ionic retro-Diels-Alder reactions
Shuai Li1, Bethany Jochim1, James E Jackson1
1Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, USA.
Abstract:
Ultrafast tunnel ionization enables femtosecond time-resolved dynamic measurements of the retro-Diels-Alder reactions of positively charged cyclohexene, norbornene, and dicyclopentadiene. Unlike the reaction times of 500-600 ps that are observed following UV excitation of neutral species, on the ionic potential energy surfaces, these reactions occur on a single picosecond timescale and, in some cases, exhibit vibrational coherence. In the case of norbornene, a 270 cm-1 vibrational mode is found to modulate the retro-Diels-Alder reaction.
Related Concept Videos
Diels–Alder vs Retro-Diels–Alder Reaction: Thermodynamic Factors
Diels–Alder Reaction: Characteristics of Dienes
Characteristics of the diene
Conformation
The simplest example of a diene is 1,3-butadiene, an acyclic conjugated π system. At room temperature, the molecule exists as a mixture of s-cis and s-trans conformers by virtue of rotation around the carbon–carbon single bond. Although the s-trans isomer is...
[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction
Diels–Alder Reaction Forming Cyclic Products: Stereochemistry
Diels–Alder Reaction Forming Bridged Bicyclic Products: Stereochemistry
C–C Bond Cleavage: Retro-Aldol Reaction
In the first step, as depicted in Figure 1, the base deprotonates the β-hydroxy ketone at the hydroxyl group to form an alkoxide ion.

