The effect of steric repulsion on the torsional potential of n-butane: a theoretical study
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The origin of the rotational barriers in n-butane and gauche conformational energy, the prototypes of steric repulsion, has been re-examined by using energy decomposition analysis. The Pauli repulsion was found to be an important factor, but not the source of the barriers and gauche/anti energy difference. Rather, it should be considered as a driving force for structural changes accompanying the rotation. The repulsion (steric) energy partly transfers into the deformation energy of ethyl fragments and also affects a decrease in electrostatic, orbital and dispersion interactions by inducing the structural changes, particularly the central CC bond lengthening, while it becomes less destabilizing during the anti-butane rotation.
Keywords:Butane / Torsional potential / Conformational analysis / Steric repulsion / Orbital interaction / Energy decomposition analysis
Source:Tetrahedron, 2015, 71, 32, 5119-5123
- Pergamon-Elsevier Science Ltd, Oxford