Stereoisomerism Flashcards
What are stereoisomers?
These have the same structural formula but a different arrangement of atoms in space.
Name the two types of stereoisomerism you will need to know.
E/Z isomerism
Optical isomerism
When does E/Z isomerism occur?
It only occurs in compounds with a C=C double bond.
Why does stereoisomerism arise around double bonds?
Because rotation about the bond is restricted and the groups attached to the carbon are therefore fixed relative to each other.
What are the two conditions for E/Z isomerism?
A C=C double bond
Two different groups attached to each carbon atom of the double bond.
What is cis-trans isomerism?
A specific case of E/Z isomerism.
What are the requirements for cis-trans isomerism?
C=C double bond
Two different groups attached to each carbon.
One of the attached groups on each carbon atom of the double bond must be a hydrogen.
What type of E/Z isomer is a cis isomer?
Z isomer
What type of E/Z isomer is trans?
E isomer
What is the E/Z naming system called?
Cahn-Ingold-Prelog nomenclature
How does the Cahn-Ingold-Prelog system work?
Atoms attached directly to the carbon atoms involved in the double bond are given priority.
What is priority based on?
Their atomic number.
What happens if the groups of higher priority are on the same side of the double bond?
The compound is a Z isomer.
What happens if the groups of higher priority are diagonally placed across the double bond?
The compound is an E isomer.
What happens as the atomic number increases?
The priority increases.
