What is a chiral carbon/ chiral centre/ chiral molecule
Molecule with 4 different groups around the C
What is a chiral carbon described as being?
Asymmetric, no plane of symmetry
What do compounds with one chiral centre exist as?
Two optical isomers, also known as enantiomers
What is one feature of enantiomers?
They are non superimposable, mirror images of each other
What are the chemical properties of optical isomers (enantiomers)?
Generally identical, however they interact with biological sensors in different ways
What are the physical properties of optical isomers?
They are identical, however they have a different ability to rotate the plane of polarised light.
What is the major difference between 2 enantiomers?
- One rotates plane polarised light clockwise and the other rotates it anticlockwise.
- can be + or -
How can the identity of an optical isomer (enantiomer) be determined?
By passing plane polarised light through a sample and observing the rotation.
What is a racemic mixture?
A mixture containing equal amounts of each enantiomer
Also known as a racemate.
Why is a racemic mixture optically inactive?
The enantiomers cancel out each other’s effect.
What happens to the plane of polarized light in a racemic mixture?
It does not change.
What is unpolarised light?
Light moving in all directions
Unpolarised light contains waves vibrating in multiple planes.
What is plane polarised light?
Light moving in one direction
Plane polarised light consists of waves that vibrate in a single plane.
What type of mixture is formed by SNI mechanisms?
Racemic mixture, if the carbocation has a trigonometry planar shape
A racemic mixture contains equal amounts of both enantiomers.
Why does a racemic mixture form from Sn1 mechanisms?
The Nucleophile is able attack from either side of the trigonal planar carbocation
Why is only one enantiomer formed from an Sn2 mechanism?
Steric hindrance means that the Nucleophile can only attack form the opposite side (rear-side/backside attack)
What is the optical activity of the product from a nucleophillic substitution reaction with a primary haloalkane?
Significant optical activity as it undergoes Sn2
What is the optical activity of the product from a nucleophillic substitution reaction with a secondary haloalkane?
No significant optical activity, as it can undergo Sn1 or Sn2
What is the optical activity of the product from a nucleophillic substitution reaction with a tertiary haloalkane?
No optical activity as it must undergo Sn1
What is optical activity?
the ability of a single optical isomer to rotate the plane of polarisation of plane-polarised monochromatic light in molecules containing a single chiral centre
