Cis-Trans Nomenclature

Cis-Trans Nomenclature names geometrical isomers by positioning similar groups on the same side (cis) or opposite sides (trans) of a double bond or ring.

When to Use:

• • Use the Cis-Trans system when each carbon in the double bond has one identical group. It is suitable for:
    • Simple alkenes with symmetrical groups,
    • Cycloalkanes, where two substituents are on the ring.

Definitions of Cis-Trans Nomenclature:

• Cis: Similar or identical groups are on the same side of the double bond or ring.
• Trans: Similar or identical groups are on opposite sides.

Example:

But-2-ene

• • In the cis isomer, the two CH₃ groups are on the same side.
  • In the trans isomer, they are on opposite sides.

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