Aldehydes and Ketones Flashcards
What reagent is used to reduce aldehydes and ketones?
- NaBH₄
- sodium tetrahydrodiborate
what are aldehydes reduced to?
- primary alcohols
what are ketones reduced to?
- secondary alcohols
what mechanism occurs during reduction of aldehydes and ketones?
- nucleophilic addition
what is meant by a polar bond?
- unequal sharing of a pair of electrons in a covalent bond due to a difference in electronegativity
what mechanism and reagents are used to form hydroxynitriles from aldehydes and ketones
- nucleophilic addition
- potassium cyanide and HCl
what are optical isomers?
- molecules that are mirror images of each other but non-super imposable
what is a chiral centre
- a single carbon atom bonded to 4 different atoms or groups
how do you distinguish between optical isomers
- they rotate the plane of polarised light in opposite directions
what is a racemic mixture and why is it optically inactive?
- 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
why do optical isomers form in a 50/50 ratio (racemic mixture) ?
- the carbonyl group is planar
- there is equal chance of the nucleophile attacking from either side
- a racemic mixture will be formed
why isn’t HCN used to make hydroxynitriles instead of KCN and HCl
- HCN reacts to form dangerous biproducts
how are reducing agents represented in equations?
[H]
Describe how to test for an Aldehyde or Ketone
Tollens reagent- If aldehyde is present, silver mirror forms
Fehlings Solution - If aldehyde is present colour change from blue to brick red
