Summary notes for AQA A-Level Chemistry Unit 3.3.7 - Optical isomerism (A-level only)
11 views 0 purchase
Course
Unit 3.3.7 - Optical isomerism
Institution
AQA
Book
AQA A Level Chemistry Student Book 2
Summary notes for AQA A-Level Chemistry Unit 3.3.7 - Optical isomerism (A-level only) by an Imperial College London MSci Chemistry graduate. Notes divided into the following sections: Optical Activity, Racemates
Summary notes for AQA A-Level Chemistry Unit 3.3.16 - Chromatography (A-level only)
Summary notes for AQA A-Level Chemistry Unit 3.3.15 - Nuclear magnetic resonance spectroscopy (A-level only)
Summary notes for AQA A-Level Chemistry Unit 3.3.14 - Organic synthesis (A-level only)
All for this textbook (13)
Written for
A/AS Level
AQA
A Level Chemistry
Unit 3.3.7 - Optical isomerism
All documents for this subject (16)
Seller
Follow
bookishresearcher
Content preview
Section 3 : Organic Chemistry
Optical Isomerism
• Optical isomerism is a form of stereoisomerism + occurs as a result of chirality in molecules.
- Stereoisomerism: same structural + displayed formulae but different arrangement of bonds in
space.
• Optical isomerism occurs in molecules which contain a carbon atom w/ 4 different atoms or groups
attached to it tetrahedrally. Such molecules exhibit optical isomerism as they are described as
asymmetric (i.e. they have no centre, plane or axis of symmetry).
• An asymmetric carbon atom is chiral + gives rise to optical isomers (enantiomers), which exist as
non super-imposable mirror images.
- This carbon atom is called a chiral or asymmetric centre.
Drawing optical isomers (enantiomers)
E.g. draw the two enantiomers of 2-hydroxypropanoic acid.
1. Draw the structure of 2-hydroxypropanoic acid + locate the chiral centre.
2. Draw 1 enantiomer in a tetrahedral shape.
3. Then draw its mirror image beside it.
Optical Activity
Optical isomers have the same chemical + physical properties as each other, except for their effect on
plane polarised light.
• A light beam consists of waves that vibrate in all planes at right angles to the direction in which the
beam is travelling. Some substances have the ability to remove from normal light all the light waves
except those vibrating in a certain plane - producing plane polarised light.
- Plane polarised light: light in which all the waves vibrate in the same plane.
Optical isomers can rotate the plane of plane polarised light - ∴ they are optically active.
• The 2 enantiomers of an optically active molecule will rotate the plane polarised light in opposite
directions.
- One enantiomer rotates it in a clockwise direction, + the other rotates in an anticlockwise
direction.
Racemates
A mixture of equal amounts of enantiomers is called a racemic mixture (racemate).
• Racemic mixtures are often formed when a chiral compound is synthesised in the laboratory by the
reaction between 2 compounds which are not chiral. This is because when 2 molecules react, there is
normally an equal chance of forming each of the enantiomers.
- Many drugs have optical isomers, + often complicated separation techniques are needed to
separate the mixture.
• Separation is dif cult because the optical isomers have similar physical properties.
• A racemate will have no effect on the plane of the light - ∴ it is optically inactive as the 2
enantiomers cancel out each other’s light-rotating effects.
fi
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 or Stuvia-credit 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 bookishresearcher. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $3.86. You're not tied to anything after your purchase.
