(c) Stereo Chemistry Flashcards
What is an isomer?
Molecules with the same molecular formula but different structural formulas.
What is a structural isomer?
When atoms are bonded together in a different order in each isomer.
When do stereoisomers occur?
When the order of the bonding in the atoms is the same but the spatial arrangement ent of the atoms is different each isomer.
How many types of stereoisomers are there?
2.
What are the 2 types of stereoisomers?
Geometric and optical.
When do geometric isomers occur?
When there is restricted rotation around a carbon to carbon double bond, or a carbon to carbon single bond in a cyclical structure.
What must there be in order for geometric isomers to occur?
2 different groups attached to each of the carbon atoms that make up the bond with restricted rotation.
How can geometric isomers be labelled?
cis or trans.
What is a cis geometric isomer?
If the 2 different groups are on the same side.
What is a trans geometric isomer?
If the 2 different groups are on different sides.
How can geometric isomers differ?
Different physical properties, e.g. melting and boiling points. They can also have different chemical properties.
How do optical isomers occur?
In compounds in which 4 different groups are arranged tetrahedrally around a central carbon atom.
If a carbon is attached to 4 different functional groups what is it known as?
Chiral carbon.
Are optical isomers symmetric or asymmetric?
Asymmetric.
How do optical isomers differ from each other?
They are non-superimposable images of each other.
How can optical isomers be described?
Enantiomers.
What is different between optical isomers?
Their effect on polarised light.
What is the same about optical isomers?
Everything bearing their effect on polarised light.
What different chemical properties do optical isomers have?
None except when is a chiral environment.
What is an example of a chiral environment?
Biological systems.
How do optical isomers affect polarised light?
They rotate polarised light by the same amount, but in opposite directions.
What does their effect on polarised light mean about optical isomers activity?
They are optically active.
What happens when optical isomers are mixed in equal amounts?
Become optically inactive.
Why do optical isomers become optically inactive when mixed in an equal amount?
The rotational effect of the plane-polarised light cancels out.
What is the mixture of optical isomers mixed together evenly called?
A racemix mixture.
