Optical Isomerism & Aldehydes and Ketones Flashcards
1
Q
Explain why a racemate has no optical activity
A
- both enantiomers rotate plane polarised light in opposite directions to the same extent
- therefore cancels out, and overall no optical activity
1
Q
What is a racemic mixture?
A
50:50 of both enantiomers
2
Q
Why do carbonyl compounds undergo nucleophilic addition?
A
- unsaturated
- good leaving group not present
3
Q
Why don’t carbonyl compounds have optical activity?
A
- carbonyl compound is trigonal planar, therefore nucleophile attacks equally from both sides
- resulting in a racemic mixture (50:50 of both enantiomers)
- both enantiomers rotate plane polarised light in opposite directions to the same extent
- therefore cancels out, and overall no optical activity
4
Q
A
5
Q
Why is HCN alone not sufficient / disadvantages of using HCN to form hydroxynitriles
A
- HCN is a weak acid; it only partially disassociates, and it provides insufficient source of CN- ions
- HCN is poisonous gas
