Stereoisomers Flashcards
Stereoisomers
Same structural formula but a different arrangement in space/ same group
What can’t happen in stereoisomers
Rotation of double bonds
Why can’t double bonds rotate
Carbon atoms in a c=c double bonds and the atoms bonded to these carbons all lie in the same plane (they’re planar).
C=C double bonds can’t rotate around them like they can around single bond. Double bonds are fairly rigid.
What does the restricted rotation around the c=c cause
A type of stereoisomers called E/Z rotation.
What is optical isomers
Different arrangements of the 4 different groups about a central c atom in a molecule -> non-identical mirror images.
Optical isomers are identical in every respect except
- They rotate plane polarised light in opposite directions.
- One may be biologically active, the other not.
What happens if we have a 50:50 mixture of optical isomers
It’s called a racemic mixture and its optically inactive because it cancels each other out.
What is each isomer called
Enantiomer
What does each enantiomer have
The same chemical and physical properties as each other but interact differently with polarised light
polarimetry
If you have a racemic mixture the overall affect
If you have a racemic mixture, the overall affect doesn’t change. It stays straight
“No effect on plane polarised light”. How correct is this statement
It’s wrong because there is an affect but half goes to right half goes to left so it cancels each other out due to it being a racemic mixture.
Explain which property of butan-2-ol allows it to have optical isomers
The 2nd carbon is the critical centre that have 4 different groups
What is a parent functional group
OH
Which part allows for optical isomerism
Critical centre
