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Ethylene Polymerizations Using Parallel Pressure Reactors and a Kinetic Analysis of Chain Transfer Polymerization
Published on: November 27, 2015
The rotational barrier in ethane: a molecular orbital study.
Ramiro F Quijano-Quiñones1, Mariana Quesadas-Rojas, Gabriel Cuevas
1Laboratory of Pharmaceutical Chemistry, Faculty of Chemistry, Autonomous University of Yucatan, 41 No. 421 Col. Industrial, C.P. 97150, Merida, Yucatan, Mexico. ramiro.quijano@uady.mx
Molecules (Basel, Switzerland)
|April 24, 2012
Summary
Computational methods reveal how molecular orbital energies in ethane influence its C-C bond rotation. Different calculation methods alter energy changes, and removing molecular orbital contributions inverts conformational preferences, highlighting their crucial role.
Area of Science:
- Computational Chemistry
- Quantum Chemistry
- Molecular Modeling
Background:
- Ethane's conformational preferences are crucial in organic chemistry.
- Understanding rotational energy barriers requires detailed molecular orbital analysis.
Purpose of the Study:
- To investigate the energy changes of occupied molecular orbitals during C-C bond rotation in ethane.
- To analyze the impact of zero-point energy (ZPE) on ethane's rotational barrier.
- To determine the influence of different computational methods and basis sets on these energy changes.
Main Methods:
- Utilized B3LYP and mPWB95 functionals, and MP2 methods.
- Employed various basis sets for high-accuracy calculations.
- Analyzed occupied molecular orbital energy profiles as a function of the C-C bond rotation angle.
Main Results:
- Specific sigma (σ) and pi (π) molecular orbitals were identified as stabilizing or destabilizing for staggered and eclipsed conformations.
- The σ(s) orbital stabilizes the staggered conformation, while another σ orbital favors the eclipsed conformation.
- π orbitals exhibit varied effects, with π(z) stabilizing both conformations and π(v) destabilizing them.
Conclusions:
- Computational method choice significantly impacts the observed energy changes during ethane's C-C bond rotation.
- The contribution of molecular orbital energies is critical for determining conformational preference.
- Excluding molecular orbital energy contributions leads to an inversion of the preferred conformation.
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