Aldehydes and Ketones Flashcards
1
Q
What reagent is used to reduce aldehydes and ketones?
A
- NaBH₄
- sodium tetrahydrodiborate
2
Q
what are aldehydes reduced to?
A
- primary alcohols
3
Q
what are ketones reduced to?
A
- secondary alcohols
4
Q
how are reducing agents represented in equations?
A
[H]
4
Q
what mechanism occurs during reduction of aldehydes and ketones?
A
- nucleophilic addition
5
Q
what is meant by a polar bond?
A
- unequal sharing of a pair of electrons in a covalent bond due to a difference in electronegativity
6
Q
why isn’t HCN used to make hydroxynitriles instead of KCN and HCl
A
- HCN reacts to form dangerous biproducts
6
Q
what mechanism and reagents are used to form hydroxynitriles from aldehydes and ketones
A
- nucleophilic addition
- potassium cyanide and HCl
7
Q
what are optical isomers?
A
- molecules that are mirror images of each other but non-super imposable
8
Q
what is a chiral centre
A
- a single carbon atom bonded to 4 different atoms or groups
9
Q
how do you distinguish between optical isomers
A
- they rotate the plane of polarised light in opposite directions
10
Q
what is a racemic mixture and why is it optically inactive?
A
- racemic mixture = 50/50 mixture of optical isomers
- the racemic mixture contains equal amounts of each enantiomer so is optically inactive as the two enantiomers rotate the plane of polarised light in opposite directions equally
11
Q
why do optical isomers form in a 50/50 ratio (racemic mixture) ?
A
- the carbonyl group is planar
- there is equal chance of the nucleophile attacking from either side
- a racemic mixture will be formed
