Optical Activity Flashcards
How do oscillations exist
In planes at right angles to the direction of travel
Transverse
What do Polaroids do
Absorb all of the oscillations except those in a single plane
Convert unpolarised light into plane-polarised light.
What does the second Polaroid sheet have and do
Horizontal lines
Only horizontally plane-polarised light can pass through
No light can pass through
What does a polarimeter do
Measure the amount of optical activity
What light source is used
A monochromatic light source
One colour
What does the plane-polarised light do
Passes through a sample tube containing some of the substance in solution
What happens if the substance is optically active
The plane of polarisation will be rotated so that is is no longer vertical
What is the second polarising filter also called
What do you do to it / how is it used
Analyser
Rotate to a position where the maximum light intensity can be seen
The angle of rotation is measured and is quoted
What do positive and negative measurements mean
If the value is positive it is clockwise
If the value is negative it is anti-clockwise
Properties of enantiomers
2 enantiomers have identical physical properties
Exception is how they react with enantiomers of other substances
How is polarised light used to identify enantiomers
They rotated the same amount but in opposite directions
Racemic definition
Mixture containing equal amounts of two enantiomers
How does optical activity provide evidence for SN1 and SN2
If a reaction occurs through SN2 or SN1 then the optical activity of the product is different from the reactant.
