3.3.8 Aldehydes and ketones Flashcards
1
Q
What do aldehydes produce when oxidised?
A
Carboxylic acids
2
Q
How do you make Tollens reagent? (3)
A
- Silver nitrate
- Drops of NaOH
- Drops of ammonia
3
Q
Tollens test + postive result
A
- Tollens + water bath.
- Silver mirror
4
Q
Fehling’s test result
A
Changes from blue to brick red precipitate
5
Q
Why does Fehling’s test work?
A
- Aldehyde can reduce Cu2+ to Cu+
6
Q
How do you get primary/secondary alcohols?
A
Reduce aldehyde/ketone using NaBH4
7
Q
Reduction of Aldehydes and Ketones mechanism name
A
Nucleophilic addition reaction (diagram)
8
Q
KCN + aldehyde/ketone mechanism
A
Same as reduction, except with CN instead of the first H+ added (diagram)
9
Q
Why is KCN used instead of HCN?
A
HCN is too toxic, and so KCN disassociates better
Remember KCN should be aqueous
10
Q
H+ H- mechanism nuance
A
- C=C = electron rich, repels H-
- H- is attracted to C+
11
Q
Dehydration of alcohols conditions
A
Concentrated H2SO4 + reflux
12
Q
How to obtain pure crystals of ketone (4)
A
- Filter
- Dissolve in small volume of hot solvent
- Leave to cool, filter
- Wash with cold water and leave to dry
