Isomers (Geometric)

Geometric or Stereoisomers exist when atoms or groups of atoms are locked into a particular geometric arrangement. cis- and trans- isomers are often the result of this geometric arrangement. When the major groups being examined are are the same side of the molecule, these groups are referred to as being cis-isomers.  In contrast, if the groups are on opposite sides of the molecule, they are referred to as being trans-isomers.

A similar naming system uses a different designation system, (E) or (Z). A more in-depth presentation for the Cahn Ingold labeling rules for Geometric Isomers can be viewed online. A geometric isomer designated Z- is equivalent to a cis-isomer, meaning that the two higher priority groups are on the same side of the double-bonded molecule, whereas an E-isomer is equivalent to the trans-designation using only carbon and hydrogen molecules.