Chemistry: Chapter 13.2 - Stereoisomerism

Stereoisomers

Same structural formula with a different arrangement of atoms in space

E/Z isomerism rules

• Must have a c=c double bond

• Must have different groups attached to each carbon atom of the double bond

Cis-trans isomerism rules

• Must have a c=c double bond

• Must have different groups attached to each carbon atom of the double bond

• One of the attached groups on each carbon atom of the double bond must be the same

Cis isomer

The matching groups are on the same side of the double bond

Trans isomer

The matching groups are opposite each other

Cahn-Ingold-Prelog rules

• The atoms attached to each carbon atom in a double bond are given a priority based on their atomic number

• If the two atoms attached to a carbon are the same then the group which has the higher atomic number at the first point of difference is given the higher priority

Z isomer

When the groups of higher priority are on the same side of the double bond

E isomer

When the groups of higher priority are diagonally placed across the double bond