Types of Isomerism
Structural isomers have identical molecular formulas but different structural formulas. This happens in several ways: through different chain arrangements, positioning of functional groups (like OH groups), or even completely different functional groups (like ketones vs. aldehydes).
Stereoisomers share the same structural formula but differ in how their atoms are arranged in three-dimensional space. The most common type is geometric isomerism, which occurs around carbon-carbon double bonds. These can be named using either cis/trans (Latin) or E/Z (German) systems.
In E/Z naming, we use the Cahn-Ingold-Prelog rules based on atomic numbers to determine priority. Groups with higher atomic numbers get higher priority. When the higher-priority groups are on opposite sides of the double bond, it's an E isomer (German "entgegen" meaning opposite). When they're on the same side, it's a Z isomer (German "zusammen" meaning together).
⭐ Remember this shortcut: "Z" for "zame zide" (same side) helps you recall that Z isomers have high-priority groups on the same side of the double bond.
