Stereoisomers: optical isomerism

Question 1

What is a chiral carbon atom?

Answer 1

a carbon atom attached to four different atoms/ groups

Question 2

what is optical isomerism?

Answer 2

Occurs when substances have the same molecular and structural formulas but are non-superimposable.

Question 3

How to use a polarimeter to distinguish between two enantiomers?

Answer 3

• Unpolarised light is passed through a polarising filter, which produces plane-polarised light.
• The plane-polarised light then passes through a solution containing the enantiomer.
• The plane-polarised light is rotated either clockwise or anti-clockwise.
• The analyser is used to measure the angle and direction of rotation of the plane-polarised light.
• The two enantiomers will rotate the plane-polarised light by the same angle but in opposite directions: one will rotate the plane-polarised light clockwise and the other anti-clockwise

Question 4

what is a racemic mixture?

Answer 4

a solution contains equal amounts of both enantiomers + no net rotation

Question 5

How do physical properties of stereoisomers compare?

Answer 5

identical apart from their interaction with plane-polarised light.

Question 6

How do chemical properties of stereoisomers compare?

Answer 6

similar chemical properties, except for their interaction with other chiral molecules