Carbonyls & Carboxylic Acids Flashcards
Difference between alkenes and carbonyls
C=O is polar ∵ O is more electronegative that C ∴ able to react with some nucleophiles whereas alkenes react with electrophiles
Carbonyl + NaBH4
= reduction to alcohols
NaBH4/H2O
Carbonyl + HCN
H2SO4/NaCN used to create HCN
= hydroxynitrile
Why can’t HCN be used directly in reactions?
Colourless, v.poisonous liquid + boils slightly over RTP ∴ hazardous
What is Brady’s reagent + what does it show?
= 2,4-DNP (dinitrophenylhydrazine)
Detects carbonyl groups - a yellow/orange precipitate is formed
Why is Brady’s reagent dissolved in methanol/H2SO4?
Solid DNP = v.hazardous ∵ friction/sudden blow = explosion
How to distinguish between aldehyde and ketone
Tollen’s reagent (AgNO3 + NH3 aq)
Aldehyde -> silver mirror
Why are some carboxylic acids more soluble than others?
The longer the chain, the less soluble it is ∵ non-polar chain has a greater effect on overall polarity of molecule
COOH + metal
Redox
= carboxylate salt + H2
How to distinguish COOH
Add carbonate (usually Na2CO3)
What’s a derivative of COOH?
A compound that can be hydrolysed to form the parent COOH
Esterification
Alcohol + COOH -> Ester + H2O
Warmed
c.H2SO4
How to make acid anhydrides
Removal of H2O between 2 COOH molecules
What is hydrolysis
Chemical breakdown of a compound in the presence of water/aq solution
Acid hydrolysis of Ester
Opposite of esterification
Heated under reflux w/dilute aq acid
= COOH + alcohol
