How do enantiomers rotate light?
1 Answer
They only rotate light that is plane polarised.....
Explanation:
They only rotate "plane polarised" light. Plane polarised light has properties that are similar in some ways to chirality.
Light emerging from a polarising filter is in the form of a wave composed of electrical components oscillating as two vectors, one rotating left to right, and one rotating right to left. They are essentially helical.
Helixes are non-superimposable, so the light is made up of what can be envisaged as a pair of enantiomeric vectors (but if you resolve them they show as oscillating in the same plane).
It means that when plane polarised light interacts with chiral centres, one of the two helixes slows down more than the other, and therefore goes out of synchronisation with the other one. Resolving the vectors demonstrates that the light rotates either left or right after passing through the chiral centre..
