Conformational Energy


The objective of this exercise is to calculate the strain energy incurred as a molecule moves between various conformations.


Use PM3, semi-empirical, calculations to calculate the strain energy of the following molecules. The strain energy can be calculated by subtracting the heat of formation of the more stable species from that of the less stable species. The strain energy should be a positive quantity.

Molecule Strain Energy (kJ/mol)

Explain whether of not your results agree with your "chemical intuition."
As we would expect, trans-butane is slightly more stable than its gauche counterpart. This is due to the steric interactions between methyl group hydrogens the latter. Likewise, chair-cyclohexane is significantly less strained than it boat counterpart, due again to the steric interactions of the C1-C4 axial hydrogens.

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