Enantiomers from Carbonyl Compounds

Question 1

What reaction mixture is formed from the 2 enantiomers after reduction of carbonyl compounds with cyanide? What are its proportions in terms of ratios of enantiomers?

Answer 1

• Racemic mixture
• 50/50 since there is a 50/50 chance of the attack happening on either side

Question 2

What enantiomer is formed when cyanide ions react with carbonyls?

Answer 2

• :CN- attacks either side of the carbonyl
• The 2 different sides can cause 2 different enantiomers to be formed

Question 3

What happens in the racemic mixture in regard to plane polarised light?

Answer 3

• Enantiomers in a racemic mixture rotate plane polarised light
• But in opposite reactions
• Since there is a 50/50 mixture, the opposite rotations cancel out
• So no effect on plane polarised light in racemic mixtures
• Ie. Optical rotation is 0

Question 4

How can we test if mixtures are racemic?

Answer 4

• If there is an effect on plane polarised light, then the sample is not racemic
• If the sample contains enantiomers of chiral compounds and there is 0 effect on polarised light, then the reaction mixture must be racemic

Question 5

What is Chiral C?

Answer 5

Carbon attached to 4 different species.