Optical Isomerism And Polarised Light

Question 1

What is a racemic mixture

Answer 1

Mixture of equal amounts of the two mirror-image forms of a chiral compound, mixture does not rotate polarised light because the two optical isomers have equal and opposite effects so they cancel each other out

Question 2

How does a light beam become polarised and why

Answer 2

After passing through a sheet of polaroid, polaroid prevents vibrations of the light waves in all but one plane so all the waves are vibrating in the same plane

Question 3

When does all the polarised beam pass through second Polaroid sheet and when does it not

Answer 3

Does if second sheet aligned in same way as first, does not if second sheet rotated through 90 degrees relative to the first

Question 4

What happens when polarised light passes through a solution of just one of a pair of optical isomers

Answer 4

It rotates the plane of polarisation

Question 5

What is the + isomer

Answer 5

Rotates the plane of plane-polarised light clockwise

Question 6

What is the - isomer

Answer 6

Rotates the plane of plane-polarised light anticlockwise

Question 7

How are the rotations measured

Answer 7

Using monochromatic light in polarimeter