Aldehydes And Ketones Flashcards
What is the functional group of an aldehyde
C=O carbonyl group on carbon 1
What is the prefix for an aldehyde
- al
What is the prefix for a ketone
- one
Why don’t ketones oxidise
There is no readily available hydrogen
What reducing agent is used to convert aldehydes/ketones to alcohols
NaBH4 in aqueous ethanol
What is the formula for Tollens reagent
(Ag (NH3)2) +
How do you differentiate between aldehydes and ketones
Tollens reagent: silver mirror forms when aldehyde is present
Fehlings solution: blue solution gores to brick red precipitate
Why does a silver mirror form
Ag+ is reduced to Ag
Why does a brick red precipitate form
Cu2+ ions are reduce to Cu2O
What forms when potassium cyanide reacts with carbonyls
Hydroxynitriles
What is the mechanism for carbonyl —> hydroxynitrile
Nucleophilic addition
What reagent is needed for mechanism carbonyl —> hydroxynitrile
KCN and dilute H2SO4
Why are KCN AND H2SO4 used as reagents for carbonyl —> hydroxynitrile mechanism
KCN provides CN- ion
H2SO4 provides H+ ion
Why can carbonyl undergo nucleophilic addition mechanisms
The carbonyl group has a dipole
What is the advantage of using KCN instead of HCN
HCN is a weak acid and will only partially ionise, so lower concentration of CN- ions
List 3 dangers of potassium cyanide
- irritant
- toxic if inhaled
- hydrogen cyanide produced if moisture’s present
Why can nucleophilic addition of HCN produce a race mate
The planar carbonyl group is attacked equally on both sides, so forms equal amount of each enantiomer
