Optical isomerism (A-level only) Revision Notes

Optical Isomerism

Optical isomerism occurs when molecules have the same molecular formula and connectivity but differ in the spatial arrangement of atoms, resulting in non-superimposable mirror images known as enantiomers. This phenomenon is primarily observed in organic compounds containing a chiral carbon atom, which is a carbon atom bonded to four different groups.

Key Concepts:

• Chiral Carbon Atoms: Identify carbon atoms that are attached to four different substituents. These are the centers of chirality in a molecule.
• Optical Isomers: Recognize pairs of enantiomers that rotate plane-polarised light in opposite directions; one isomer rotates light clockwise (dextrorotatory) and the other counterclockwise (levorotatory).
• Plane-Polarised Light: Understand how optical isomers interact with light, leading to their unique optical activities.
• Distinction from Structural Isomerism: Differentiate optical isomerism from structural isomerism, where structural isomers have different connectivity of atoms rather than just spatial arrangement.