8: Carbonyl Compounds Flashcards
(23 cards)
What is a carbonyl group
C=O
What does the term carbonyl compound refer to
Aldehydes and ketones
What is the oxidising agent for oxidising primary and secondary alcohols
Hot, aqueous, acidic potassium dichromate
What does oxidation of a primary alcohol form
Aldehyde
What does extended oxidation of a primary alcohol produce
Carboxylic acid
What does oxidation of a secondary alcohol form
Ketones
What is the main difference between a C=C bond and a C=O
C=O is polar as oxygen is much more electronegative than carbon
Why are carbonyl compounds polar
Because the oxygen is very electronegative
Why do carbonyl compounds have a higher melting point than alkanes and alkenes of similar size
They can form permanent dipole-dipole bonds due to the dipole
Can carbonyl compounds form hydrogen bonds with more of the same carbonyl compound
No, there is no H bonded to the O
Can carbonyl compounds form hydrogen bonds with other compounds such as water
Yes
What is formed when aldehydes or ketones react with 2,4 DNP
Yellow or orange precipitate
How to use 2,4-DNP to identify a specific aldehyde or ketone
- Add 2,4-DNP and collect precipitate by filtration.
- Purify the solid by recrystallisation
- Measure the melting point of the crystals
- Compare m.p. with batabase - to identity the original aldehyde/ ketone
What is the process of Recrystallisation
- Dissolve the solid in a minimum amount of hot solvent
- cool the solution: major product crystallises, impurities stay in solution
- collect the crystals by filltration
- Wash crystals with cold solvent
- leave to dry
How to distuingish between aldehydes and ketones with aqueous acidic potassium dichromate
Aldehydes will be oxidised
Ketones won’t
What is the result of Tollen’s reagent being added to an aldehyde
The aldehyde is oxidised to a carboxylic acid
The silver ions are reduced to metallic silver which is deposited on the side of the container as a shiny silver mirror
What does the reduction of a carbonyl form
An alcohol
What type of reaction is reduction of carbonyls
Nucleophillic addition
What does H^- act as in the reduction of a carbonyl
A nucleophile
What does the intermediate in the reduction of a carbonyl act as
Acts as a base as it takes a H^+ from the aqueous solvent water to complete the reaction
What is the product of HCN and an aldehyde or ketone
A hydroxynitrile
What is the reagent for the reaction of addition of HCN
Acidified aqueous sodium cyanide solution
How does CN^- act as a catalyst in the addition of HCN to and aldehyde or ketone
It is used up in the first step but regenerated in the second
