Optical Isomerism (OCR A Level Chemistry A): Flashcards
Exam code: H432
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Define stereoisomers
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Cards in this collection (14)
Define stereoisomers
Stereoisomers are molecules that have the same structural formula but have their atoms arranged differently in space.
Define chiral centre
A chiral centre is a carbon atom bonded to four different atoms or groups of atoms, giving rise to optical isomers.
What structural feature makes a carbon atom a chiral centre?
A carbon atom bonded to four different atoms or groups of atoms is a chiral centre.
How can you confirm a carbon atom is NOT a chiral centre?
If the carbon is bonded to two identical atoms or groups of atoms, it cannot be a chiral centre.
Define enantiomers
Enantiomers are the two optical isomers of a chiral molecule, which are non-superimposable mirror images of each other.
Chiral centres are commonly marked with an .......... in structural drawings.
Chiral centres are commonly marked with an asterisk in structural drawings.
A carbon atom bonded to .......... different atoms or groups of atoms is called a .......... carbon.
A carbon atom bonded to four different atoms or groups of atoms is called a chiral carbon.
When identifying chiral centres from a molecular formula, what should you do first?
Draw the molecule as a condensed structural formula or displayed formula so all bonds and groups are visible.
Why does a molecule with a chiral centre exist as two distinct optical isomers?
The four different groups on the chiral carbon can be arranged in two non-superimposable ways, producing two enantiomers that are mirror images of each other.
True or False?
A carbon atom bonded to two identical groups can be a chiral centre.
False.
A chiral centre requires four different groups; two identical groups mean the carbon cannot be a chiral centre.
True or False?
Enantiomers are superimposable mirror images of each other.
False.
Enantiomers are non-superimposable mirror images, meaning one cannot be placed on top of the other to give an identical arrangement.
In a 3D stereochemical drawing, what does a solid wedge bond represent?
A solid wedge represents a bond coming out of the plane of the paper towards the viewer.
What two types of stereoisomerism exist in organic chemistry?
Geometrical (E/Z) stereoisomerism
Optical stereoisomerism
True or False?
A dotted line in a stereochemical drawing represents a bond receding behind the plane of the paper.
True.
A dotted line (or hatched wedge) shows a bond going behind the plane of the paper, away from the viewer.
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