Stereo Chemistry Flashcards
When do Structural Isomers Occur?
When the atoms are bonded together in a different order in each isomer
When do Stereoisomers occur
When the order of the bonding in atoms is the same but the spatial arrangement is different in each isomer.
What are the types of Stereoisomers?
Geometric isomers and Optical isomers.
Geometric isomers can occur when….
There is restricted rotation around a C=C double bond or a C-C Single bond in a cyclic compound.
A Geometric Isomer must have…….
Two different groups attached to each of the carbons that make up the bond with restricted rotation.
Describe a ‘Cis’ Geometric isomer
A molecule that has the same group on the same side as the bond
e.g. \__/
Describe a ‘Trans’ Geometric isomer
A molecule that has the same group on different sides as the bond
e.g. \ __
\
Geometric isomers differ in
- Physical properties (e.g. melting and boiling points)
- Chemical Properties
When do optical isomers occur?
In compounds in which 4 different groups are arranged tetrahedrally around a central/chiral carbon atom
Optical isomers are
Asymmetric, Non-superimposable Mirror Images of each other
Another name for optical isomers is
Enantiomers
Optical isomers have identical……
- Physical properties (except for their effect on plane-polarised light)
- Chemical properties (except when in a chiral environment such as that found in biological systems (only one optical isomer is usually present))
How do optical isomers rotate plane polarised light?
By the same amount but in opposite directions (and so optically active)
Describe a Racemix Mixture
When mixed in equal amounts optical isomers are optically inactive because the rotational effect of the
plane-polarised light cancels out
