Conformational analysis

Conformational analysis studies the shapes a molecule can adopt through rotation around single bonds and compares their energies and populations.

Dihedral angle: The angle between two planes defined by four atoms connected in sequence. It measures rotation around a bond and identifies a molecule’s conformation.
Conformation: A spatial arrangement of atoms in a molecule that can change without breaking covalent bonds. It is the kind of molecular shape that conformational analysis compares.
Ethane: The simplest alkane with a carbon–carbon single bond and formula C₂H₆. Its staggered and eclipsed forms provide the simplest model of bond rotation.
Curtin–Hammett principle: A principle relating product ratios to transition-state free energies when rapidly interconverting reactants form products irreversibly. It explains why the most populated conformer need not yield the major product.
Conformational isomerism: The existence of distinct molecular conformations that interconvert through rotations or other low-energy motions. It names the phenomenon whose structures and energetic relationships the analysis describes.
Torsional strain: An increase in molecular energy caused by unfavorable interactions between bonds on adjacent atoms. It makes some rotations less favorable, especially in staggered and eclipsed comparisons.
Newman projection: A drawing that represents a molecule viewed along a selected bond. It makes rotation around a bond and substituent relationships easy to inspect.
Butane: A four-carbon alkane whose central bond rotation produces distinct staggered conformations. Its anti and gauche forms show how steric interactions affect conformer energies.
Conformational selection: A binding mechanism in which a ligand binds a pre-existing protein conformation from an ensemble. Protein conformer populations can influence which structures bind a ligand.
Atropisomerism: Stereoisomerism caused by hindered rotation about a single bond, producing isolable or slowly interconverting forms. It marks cases where bond rotation is restricted enough to preserve distinct conformers.

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