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Updated: May 30, 2026

Isolating Free Carbenes, their Mixed Dimers and Organic Radicals
Published on: April 19, 2019
Interconversion study in 1,4-substituted six-membered cyclohexane-type rings. Structure and dynamics of
Alex D Bain1, Maximo Baron, Steven K Burger
1Department of Chemistry and Chemical Biology, McMaster University, Hamilton, Ontario L8S 4M1, Canada. bain@mcmaster.ca
The study investigates the dynamic interconversion between cyclohexane conformations in trans-1,4-dibromo-1,4-dicyanocyclohexane. Variable-temperature NMR and computational methods reveal the activation enthalpy for this dynamic process.
Area of Science:
- Organic Chemistry
- Physical Chemistry
- Computational Chemistry
Background:
- Cyclohexane exhibits conformational flexibility, interconverting between chair forms.
- 1,4-disubstituted cyclohexanes present unique conformational dynamics and potential for unusual behavior.
- trans-1,4-dibromo-1,4-dicyanocyclohexane serves as a model for studying these dynamics.
Purpose of the Study:
- To investigate the conformational interconversion in trans-1,4-dibromo-1,4-dicyanocyclohexane.
- To understand the influence of 1,4-disubstitution on cyclohexane ring dynamics.
- To determine the kinetic and thermodynamic parameters of the conformational exchange.
Main Methods:
- Variable-temperature proton Nuclear Magnetic Resonance (NMR) spectroscopy.
- X-ray diffraction studies on crystalline solids.
- Computational chemistry methods for potential energy surface calculations.
Main Results:
- The molecule exhibits a significant dipole moment in solution despite a centrosymmetric crystal structure.
- Low-field NMR spectra show a single line at room temperature, indicating fast exchange between conformations.
- Variable-temperature studies yielded an activation enthalpy of 62 kJ/mol for the interconversion process.
Conclusions:
- Conformational dynamics in 1,4-disubstituted cyclohexanes are significant and influence molecular properties.
- The observed NMR behavior is attributed to rapid interconversion between axial and equatorial bromine conformations.
- Computational methods provide detailed insights into the chair-chair interconversion mechanism.
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