optical isomerism Flashcards
what is optical isomerism?
a form of stereoisomerism and occurs as a result
of chirality in molecules
what is stereoisomerism?
same structural and displayed formulae but different
arrangement of bonds in space
what is a chiral centre/carbon?
a carbon with 4 different groups/atoms attached to it tetrahedrally
- such molecules exhibit optical isomerism as they are asymmetric
optical isomers are also called…
enantiomers - they exist as non super-imposable mirror images
optical isomers have… (properties)
the same chemical + physical properties as each other, except for their effect on plane polarised light
what do light beams consist of?
waves that vibrate in all planes
what is plane polarised light?
light in which all the waves vibrate in the
same plane
- Some substances have the ability to remove all the light waves except
those vibrating in a certain plane - producing plane polarised light
what effect do optical isomers have on plane polarised light?
they can rotate plane polarised light - they are described as being 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, and the other
rotates in an anticlockwise direction
what is a racemic mixture?
a mixture of equal amounts of enantiomers
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
what effect does a racemic mixture have on a plane of light?
a racemate will have no effect on the plane of the light - therefore it is optically inactive as the 2 enantiomers cancel out each other’s light-rotating effects
