Geometric Isomers E-Z Notation

Edexcel AS-level ChemistryIntroduction to Organic ChemistryLesson 13 of 13

The cis-trans names only work when the same group is on both carbons of the C=C. The E-Z system names every geometric isomer, using the Cahn-Ingold-Prelog (CIP) priority rules.

Step 1: look at one carbon of the double bond. Of its two groups, the one whose directly attached atom has the higher atomic number has the higher priority.
Step 2: do the same for the other carbon.
Step 3: if the two higher-priority groups are on the same side, the isomer is Z (German zusammen, together). If they are on opposite sides, it is E (entgegen, opposite).

More in Introduction to Organic Chemistry

• Functional Groups
• Homologous Series
• Naming Organic Compounds
• Practice Question - 1
• Practice Question - 2
• Practice Question - 3
• Structural Isomerism
• Stereoisomerism

All 13 lessons in Introduction to Organic Chemistry · All Edexcel AS-level Chemistry topics