Edexcel A-Level Chemistry 9CH0
Atomic Structure and the Periodic Table
Bonding and Structure
Inorganic Chemistry and the Periodic Table
Formulae, Equations and Amounts of Substance
Organic Chemistry I
Modern Analytical Techniques I
Energetics I
Kinetics I
Equilibrium I
Acid-Base Equilibria
Energetics II
Redox II
Transition Metals
Kinetics II
Organic Chemistry II
Organic Chemistry III
Organic Chemistry II
Chirality
- 3 things to know
- Papers 2 and 3
Overview
Chiral centres and optical isomers, how they rotate plane-polarised light, racemic mixtures, and using the optical activity of the product to tell an Sₙ1 mechanism through a planar carbocation from an Sₙ2 mechanism with inversion.
What you need to know
Answer each one before you reveal it.
What happens to the configuration at the chiral centre during an Sₙ2 reaction?
What molecular feature gives rise to optical isomerism?
Questions from this subtopic
Each one with the model answer underneath.
- 1
What molecular feature gives rise to optical isomerism?
Model answer
Handedness in a molecule carrying one chiral carbon
- 2
Define a chiral centre.
Model answer
An asymmetric carbon atom bonded to four different groups
- 3
What is the relationship between two optical isomers?
Model answer
They are non-superimposable mirror images of each other
- 4
What is optical activity?
Model answer
One optical isomer turns plane-polarised light of a single wavelength clockwise; its mirror image turns it by an equal angle the other way.
- 5
What is a racemic mixture?
Model answer
A mixture containing equal amounts of both optical isomers (enantiomers)
- 6
Why does a racemic mixture show no net optical activity?
Model answer
Because the rotations of the two enantiomers cancel out
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