Summarised information from topic 3.3.9 for AQA A-Level Chemistry, including key terms and diagrams to help you understand the subject in a concise and accurate way.
3.3.7 Optical Isomerism
Stereoisomerism and Chirality
Stereoisomers have the same formula, and the atoms are joined in the same order. However, they have
different special arrangements. Optical isomerism is a form of stereoisomerism.
Optical isomers are formed when a molecule (in this case, organic) contains a chiral carbon. A carbon atom
is chiral if it is bonded to four different molecules or groups. In this case, the four atoms could be arranged
in two different ways within the 3D structure, and no rotation of either molecule will make the structures
identical – they are non-superimposable (mirror images).
This can also be described using chirality. A molecule with a plane of symmetry is achiral, and a molecule
with no plane of symmetry is chiral. The central carbon atom that causes this lack of symmetry is the
chiral centre.
Enantiomers
Optical isomers are named because of their effect non plane polarised light. Simple substances which
display optical isomerism exist as two isomers known as enantiomers.
• A solution of one enantiomer rotates the plane of polarisation in the clockwise direction.
• A solution of the other enantiomer rotates the plane of polarisation in the anti-clockwise direction.
Racemic Mixtures
If a solution contains an exact 50/50 split of enantiomers, then the plane will appear not to rotate, as the
two opposites cancel each other out. This solution is known as a racemic mixture or racemate.
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller hannahthompson. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for £3.99. You're not tied to anything after your purchase.