Symmetry and Conformation of the Cycloalkanes

The conformations of the cycloalkanes and related molecules are expressed in terms of a symmetry-adapted set of coordinates. The coordinates measure the deviation of the molecule from a planar regular structure. Use of these coordinates leads to relatively simple expressions for the conformational energy and to a method for finding possible paths for free pseudorotation. We conclude that conformations with low symmetry are more likely to pseudorotate with low energy barriers than are conformations with high symmetry. Selection rules for electric dipole transitions among the energy levels characteristic of pseudorotation are derived. The conformational energy surface is discussed in detail for a number of the smaller cycloalkanes. Description of the conformation of very large rings in terms of our coordinates is expected to be incomplete and our method will consequently not be applicable to these rings.