Optical Isomerism

Question 1

How to calculate partial pressure?

Answer 1

mole fraction X total pressure

Question 2

How to calculate mole fraction?

Answer 2

no. of moles of a gas/total no. of moles

Question 3

What are the different types of stereoisomerism?

Answer 3

• Geometric Isomers (E/Z)
• Optical

Question 4

Definition of a structural isomer?

Answer 4

Same molecular formula but different structural formula

Question 5

Definition of a stereoisomer?

Answer 5

Same structural formula but different arrangement of atoms in space

Question 6

What is optical isomerism?

Answer 6

they rotate the plane of polarised light when enantiomerically pure (only contains 1 optical isomer)

Question 7

Definition of an Enantiomer

Answer 7

Each optical isomer

Question 8

Definition of a racemic mixture

Answer 8

Mixture which contains equal quantities of enantiomers/optical isomers

Question 9

Mechanism for the reduction of propanal?
Equation?

Answer 9

Question 10

Reagent used for reduction of aldehydes + ketones?
Type of Mechanism?
Conditions?

Answer 10

NaBH4
Nucleophilic addition
Acidic Solvent

Question 11

Mechanism for the reduction of butanone?
Equation?

Answer 11

Question 12

Reagent used for reaction of aldehydes + ketones with CN?
Type of Mechanism?
Conditions?

Answer 12

KCN
Nucleophilic addition
Acidic Solvent

Question 13

Mechanism for the reaction of propanal with KCN?
Equation?

Answer 13

Question 14

Mechanism for the reaction of butanone with KCN?
Equation?

Answer 14

Question 15

Why can nucleophilic addition to aldehydes + asymmetrical ketones result in a racemic mixture of optical isomers?

LOOK AT QUESTION ON SHEET DID ON FRIDAY

Answer 15

• The C=O bond is planar
• So a 50:50 chance of nucleotide attacking from one side or the other
• Results in equal proportions of each isomer

Question 16

State and explain how you could distinguish between two enantiomers?

Answer 16

• Plane polarised light
• Rotated in opposite directions