Chapter 4: 4.6 Stereoisomers IIIb - Optical Isomers Flashcards
What are optical isomers?
Two different molecules with one or more stereocentres or a molecule with two or more stereocentres within itself
Why are they called optical isomers?
We use something called optical activity to “quantify” chirality
If a molecule is chiral, in optics, it will…
Rotate plane polarized light
Define:
Enantiomers
Non-superimposible mirror images
In order to have enantiomers, a molecule must have…
One or more chiral centres
True or False:
Enantiomers differ at all chiral centers
True
How do enantiomers of each other rotate light?
Rotate plane polarized light with equal magnitude by opposite sign
Define:
Diastereomers
Not mirror images at all
In order to have diastereomers, a molecule must have…
Two or more chiral centres
True or False:
Diastereomers differ at all chiral centres
False, diastereomers differ at some but not all chiral centres
Is there a relationship for optical activity and diastereomers?
No there is not
Define:
Meso Compounds
A molecule with two or more chiral centres and an internal plane of symmetry
True or False:
A meso compound rotates plane polarized light
False, they do not rotate plane polarized light
What is a good method to check if a molecular is a meso compound?
Assign R/S nomenclature for the chiral centres
* A meso compound will have opposite configurations (one R and one S)
