OPTICAL ISOMERISM Flashcards
(16 cards)
What are isomers? (1)
are compounds with the same molecular formula but have different molecular structure or a different arrangement of atoms in space.
what are the different types of structural isomers? (3)
-have different functional groups
-have functional groups attached to the main chain at different points
-have a different arrangement of carbon atoms in the skeleton of the molecule
what is stereoisomerism? (1)
where two (or more) compounds have the same structural formula, they differ in the arrangement of the bonds in space.
what are the types of stereoisomerism? (2)
- E-Z isomerism
- optical isomerism
how do optical isomers occur? (1)
occur when there are four different substituents attached to one carbon atom, this results in two isomers that are non-superimposable mirror images of one another but are not identical.
what are optical isomers? (1)
a pair of molecules that differ in the way they rotate the plane of polarisation of polarised light - either clockwise isomer (+) or anticlockwise isomer (-)
what are optical isomers said to be? (1)
are said to be chiral and the two isomers are called a pair of enantiomers
explain the structure of an enantiomer. (1)
the carbon bonded to the four different groups is called the chiral centre or the asymmetrical carbon atom.
how do you spot a chiral molecule? (1)
because it contains at least one carbon atom that has four different groups attached to it.
why does optical isomerism happen? (1)
because the isomers have three-dimensional structure so it can only be shown by three-dimensional representation or by models.
what does light consist of? (1)
consists of a vibrating electric and magnetic field, if a light passes through a specific filter called a polaroid all the vibrations are cut out except those in one plane.
what happens when light hits a polaroid filter? (1)
the light is now vertically polarised and it will be affected differently by different optical isomers of the same substance.
what can optical rotation be measured by? (1)
a polarimeter
what is the first stage of using a polarimeter? (1)
polarised light is passed through two solutions of the same concentration, each containing a different optical isomer of the same substance.
what is the second stage of using a polarimeter? (1)
one solution will rotate the plane of polarisation through a particular angle, clockwise. this is the (+) isomer
what is the third stage of using a polarimeter? (1)
the other will rotate the plane of polarisation by the same angle, anticlockwise, this is the (-) isomer
