Conformational isomerism

“Molecules that differ from each other by rotation about single bonds are called conformational isomers or conformers. Derek H. R. Barton (…) showed that the chemical and physical properties of complicated molecules can be interpreted in terms of their specific or preferred rotational arrangements and that a knowledge of the conformations of molecules is crucial to understanding the stereochemical basis of many reaction.”

“Theoretical and computational chemistry contribute greatly to our understanding of conformational preferences of both stable molecules and transition states. Molecular mechanics methods (classical or force field) help define the conformational preferences of reactants and products. These methods are empirical, having been parameterized to reproduce experimental structures and energies and/or data provided by high-level quantum mechanical calculations.”