O- Aldehydes & Ketones Flashcards
1
Q
Why is a racemic mixture formed in nucleophilic addition? [3]
A
- hydroxylnitriles w/ chiral C
- trigonal planar
- equal chance of attack by nucleophile from above + below plane
2
Q
Options in drug design if only one enantiomer in the racemic mixture is useful as a drug.
A
- separate 2 isomers- ❕ v. difficult + expensive
- sell drug as racemic mixture- ❕ half of drug wasted
- design synthesis only produce correct isomer- ❕ can involve ↑ expensive starting materials
3
Q
What reagents are represented by the symbol [O]?
A
oxidising agents
4
Q
Why is the reaction slow for dissociation of HCN?
A
weak acid- HCN (aq) ⇌ H+ (aq) + :CN- (aq)
- ↓ conc. of CN- ions
5
Q
Why is KCN used instead of HCN in nucleophilic addition?
A
toxic
6
Q
Why is KCN adjusted to be pH4-5 in nucleophilic addition?
A
provides H+
7
Q
Why can’t ketones be easily oxidised into carboxylic acids?
A
- C-C must be broken
- strong
- only stronger oxidising agents can break hydrocarbon chain –> shorter chain + CO2 + water
8
Q
Give an example of a reducing agent that would reduce both aldehydes and ketones.
A
- NaBH4 - sodium tetrahydridoborate
- reduced to alcohol
9
Q
Why does NaBH4 reduce C=O but not C=C?
A
- repelled by high e- density in C=C
- attracted to Cδ+ in C=O
10
Q
A
