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Aldehydes + Ketones - Coggle Diagram
Aldehydes + Ketones
Uses
Aldehydes
natural flavouring agents in food
- benzaldehyde (odour + flavour almonds)
- cinnamaldehyde (o+f of cinnamon)
-
propanone (acetone)
- volatile liquid
- completely miscible with water
+useful solvent for organic compounds
Structure
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carbonyl bond
POLAR
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causes
- δ+ on carbon
- δ- on oxygen
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Physical Properties
Solubility in Water
- can't H bond with each other
- A+K have highly polar molecules
- don't have H atoms directly attached to O
why? -
- they are H-bond acceptors
- but not H-bond donors
- so cannot H-bond w each other
solubility falls with chain length
- as chain increases
- long hydrocarbon chain get in way
- force themselves between water molecules
- break relatively strong H-bonds between water molecules
- solubility decreases
- can H bond with water
- between polar H of water
- and lone pair on O of carbonyl
group
Boiling Points
higher than alkanes
even though similar RMM
- VDW + permanent dipole-dipole attractions
= between the carbonyl groups on neighbouring aldehyde molecules
methanal higher than ethanal
- as length of C chain increases
- BP increases
- greater no. of electrons
- stronger VDW forces between molecules
K higher than isomeric A
- due to position of carbonyl
- carbonyl @ end (A) - gives longer
non-polar section
- more effective VDW forces
- less effective permanent DD
branched chains lower than straight chain
- less interactions between molecules
- less effective permanent DD attractions
lower than alcohols
- alcohols have hydrogen bonds
= between the hydroxyl groups on neighbouring alcohol molecules
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