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"Constitutional isomers are molecules that have the same molecular formula but a different arrangement of atoms. Stereoisomers have the same connectivity but a different stereochemistry—the spatial orientation of atoms. Alkenes and cycloalkanes can have the cis- or trans- configuration, with functional groups either on the same (cis) side of the molecule or opposite (trans) side. Tetrahedral carbon atoms with various attachments can have chirality, two enantiomers that form non-superimposable mirror images. These can be identified by looking for planes of symmetry and differentiated using the Cahn-Ingold-Prelog Rules for nomenclature. Fischer projections can make it easier to draw different stereoisomers. The lecture concludes by discussing the physical properties of diastereomers, optical separation of enantiomers, and racemic mixtures (1:1 ratio of enantiomers) of chiral compounds. Stereochemistry. Isomers. Alkenes. Cycloalkanes. Tetrahedral Carbon: Superimposable (Identical). Tetrahedral Carbon: Non-Superimposable (Stereoisomers). Chirality. Stereoisomers. Chiral. Achiral. Superimposable, Non-Superimposable, Chiral, and Achiral. Nomenclature. Cahn-Ingold-Prelog Rules. Drawing Stereoisomers. Drawing (S)-2-bromopentane. Drawing the Enantiomer of (S)-2-bromopentane: Method 1. Drawing the Enantiomer of (S)-2-bromopentane: Method 2. Fischer Projections. Drawing Fischer Projection. Use of Fisher Projection: Assigning Configuration. Molecules with Two Chiral Carbons. Fischer Projection of A. Diastereomers. Draw All Stereoisomers of 2,3-dichlorobutane. Molecules with Two Chiral Centers. Optical Activity. Chiral Molecules. Angle of Rotation. Achiral Species. Physical Properties of Stereoisomers. Enantiomers. When Do Enantiomers Behave Differently?. Racemic Mixtures. Resolution. Unequal Mixtures of Enantiomers. Enantiomeric Excess (ee). Unequal Mixture of Enantiomers. "
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