Optical isomerism Flashcards
When does an optical isomer occur?
When there is a chiral centre in a molecule
What is a chiral centre?
Carbon with 4 different groups attached
How is a chiral centre marked?
With an asterisk
When does chiral apply?
If no. of C is different, regardless of same functional group
What is optical isomerism?
Th existence of 2 non-superimposable mirror images of a molecule which arises as a result of having a chiral atom in the structure
What do you need to draw optical isomers?
Wedge bonds to clearly show 3D tetrahedral arrangement
How do you draw optical isomers?
- Find the chiral caron and draw it is the central atom
- Draw the 4 bonds for a tetrahedral arrangement
- Add in the 4 different groups onto edge of bonds using structural formula
4.Draw a mirror line - Mirror the entire molecule
What is the general chemical behaviour of optical isomers?
The same, but rotate the plane of plane-polarised light in opposite direction
When does the behaviour of optical isomers change?
In chiral environments
What is an example of a chiral environment?
Human bodies
What is an example of chiral molecules having different reactions?
(+) limonene smells like orange and (-) limonene smells like lemon
What is the effect of our bodies being chiral?
Chiral molecules may have different effects
What are examples of chiral molecules having different effects?
One may be ineffective so a large dose is needed for required effects, or harmful side effects
How are molecules made?
As a mixture of optical isomers as test tubes are non-chiral so can’t control direction of approach of attacking species
How are single optica isomers produced in the body?
by enzymes are proteins are chiral and direction can e controlled
How can single optical isomers made?
Using enzymes or bacteria, using chiral starting materials, mimicking natural systems and physical separation
How can enzymes or bacteria be used to make single optical isomers?
Promotes steroselectivity
How can using chiral starting materials produce single optical isomers?
Using naturally produced amino acids or sugars for chiral pool synthesis
How can you mimic natural systems to make single optical isomers
Using chemical chiral synthesis or chiral catalysts
What is the issues with physical separation?
It is laborious, wasteful and expensive
What are advantages of single optical isomer drug production?
Reduces possible side effects and improved pharmacological activity as smaller doses needed
What is a limitation of single optical isomer drug production?
Increased costs due to difficulty of production and separation
