Stereochemistry III : Conformational Isomerism in 3D.

Introduce conformational isomerism and distinguish it from structural isomerism, explaining connectivity versus orientation and how rotation about bonds creates stereoisomerism.

Explore conformational isomerism in ethane by rotating around the carbon–carbon bond, revealing eclipsed and staggered forms and the associated van der Waals strain and energy changes.

Explore torsional and Van der Waals strain, eclipsing interactions, and Newman projections to understand how dihedral angles influence energy minima and maxima in conformations.

Describe how angle strain, torsional and eclipsing strains arise in cyclic rings, and how chair and boat cyclohexane conformations, butterfly and envelope structures reduce ring strain.

Explore intramolecular hydrogen bonding between electronegative substituents and hydrogens that stabilizes the gauche form. Note energy factors—van der waals, eclipsing, hydrogen bonding, and bulky groups—that shape gauche versus anti conformations.

Explore butane conformations around the C2-C3 bond, including gouge, anti, partially eclipsed, and fully eclipsed forms, and explain how Vanderwaals interactions shape their energy minima and stability.

illustrate branched alkanes and conformational isomerism in three-dimensional structures, using front and back views and c2c3 relationships to show how methyl and isopropyl groups influence energy.

This lecture explains cyclohexane conformations, focusing on ring strain from non-ideal angles and 1,3-diaxial repulsions. Ring flipping between chair conformations minimizes strain, yielding chair form over the boat form.

Explores cyclohexane conformations, detailing axial and equatorial hydrogens in the chair form, the chair-boat interconversion, and how hydrogen positions and 109° interactions affect stability.

The lecture analyzes cyclohexane conformations, showing chair as the most stable form, boat and twist-boat as higher energy due to eclipsing and flagpole interactions, and half-chair as least stable.

examine the stability of methyl cyclohexane by comparing axial and equatorial positions, noting 1,3-diaxial interactions and repulsions. prefer equatorial placement for bulky groups to minimize diaxial interactions.

Explore conformational isomerism in cyclohexanes, focusing on dimethyl cyclohexanes, axial and equatorial positions, and chair interconversions. Highlight bulky group effects that favor equatorial placement to minimize steric interactions.

Explore the conformation of butadiene by examining rotation around bonds and comparing different orientations, with references to propane as a comparative example.

examine conformational isomerism in propene and acetaldehyde by showing rotation around adjacent single bonds while the carbon–carbon double bond remains fixed, yielding distinct conformations.

Learn how conformations at energy minima determine cyclohexane properties like dipole moment and solubility, using weighted averages across conformers and equilibrium populations.