What is the primary purpose of the Cahn, Ingold and Prelog rules?

The Cahn, Ingold, and Prelog rules are primarily used to assign priority to the substituents attached to a double bond in alkenes, which is essential for determining the configuration of these isomers. This system categorizes alkenes as either E (entgegen) or Z (zusammen) based on the relative positions of the highest priority substituents across the double bond. The rules consider the atomic number of the atoms directly attached to the double-bonded carbons; the substituent with the higher atomic number has higher priority.

This method allows chemists to clearly describe the spatial arrangement of groups in molecular structures, which is crucial for understanding reactivity and properties of different isomers. This coding of isomer configurations helps in discussions related to stereochemistry and reveals information about how these molecules might behave chemically in reactions.