AC8: Carbonyl compounds Flashcards
List the carbonyl compounds
aldehydes and ketones NOT carboxylic acids
What is the carbonyl group
C=O
What is the C=O group called
carbonyl group
Describe the bonding of a carbonyl group
sideways overlap of p-orbitals between C-O resulting in a localised π - bond and so a double bond
What does an aldehyde oxidise to
carboxylic acid
What does a ketone oxidise to
No reaction
what reagents and conditions are needed to oxidise an aldehyde
hot, aqueous, acidified potassium dichromate
How can aldehydes/ketones be reduced, state reagents and conditions
NaBH4 - hydride
2 [H]
and H2O
What do aldehydes/ketones reduce to
their corresponding alcohol
By what mechanism do aldehydes/ketones reduce to alcohols
nucleophilic addition
what is formed when HCN reacts with carbonyl compounds, and what reagents and conditions are required for this
hydroxynitrile is formed
acidified NaCN (aqueous H2SO4 and aqueous NaCN) are the reagents, provides a potent nucleophile CN-
By what mechanism does HCN react with carbonyl compounds
nucleophilic addition
How do you test for carbonyl compounds
1- add one drop of suspected aldehyde/ketone to 2 cm depth of 2,4-DNPH (pale orange solution) in a test tube
2 - a yellow/orange precipitate forms in the presence of a carbonyl compound
3 - filter, wash and recrystallise the ppt. Measure the mpt and compare with those of known 2,4-DNPH (Brady’s reagent) derivatives of known carbonyl compounds to help identify the carbonyl compound
How do you test for aldehydes
1 - Add one drop of suspected aldehyde to the Tollens’ reagent [O] and then warm in a water bath
2 - a silver mirror forms on the inside surface of the test tube, if an aldehyde is present
What is Tollens’ reagent
ammoniacal silver nitrate
(silver nitrate dissolved in ammonia)
