3.7- Naming and isomerism

Question 1

What is the definition of a structural isomer

Answer 1

Same molecular formula but a different structure

Question 2

Give the definition of optical isomerism

Answer 2

Occurs in a carbon with 4 different groups of atoms attached to a carbon that is called a chiral carbon

Question 3

What occurs when the amount of each enantiomers are 50/50

Answer 3

They are called a racemate, each enantiomer rotates light by the same amount in the opposite direction however they both cancel eachother out in a racemate, hence a racemate will not rotate plane polarised light

Question 4

How is a racemate formed

Answer 4

Will be formed in a reaction when a reactant or intermediate has a trigonal planar group in the molecule is approached from both sides by an attacking species

Question 5

Give an example of a reaction where a racemate is formed

Answer 5

The nucleophillic addition of HCN to aldeydes and ketones
The electrophillic addition of HBr to an alkene that is unsymmetrical

Question 6

Give the example of differing drug action in the molecule of thalidomide due to its enantiomers

Answer 6

One enantiomer of thalidomide causes birth defects in unborn children whilst the other had useful sedative problems.