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Contents
Aldehydes and Ketones ........................................................................................................................ 2-3
Carbonyl Group ................................................................................................................................................................................................... 2
Oxidation of Alcohols ........................................................................................................................................................................................ 2
Reduction of Carbonyls.................................................................................................................................................................................... 2
Nucleophilic Addition ....................................................................................................................................................................................... 3
Reduction of Carbonyls ..................................................................................................................................................................................... 3
Addition of :CN- ..................................................................................................................................................................................................... 3
Esters ................................................................................................................................................... 4-6
Carboxylic Acids.................................................................................................................................................................................................. 4
Esters ....................................................................................................................................................................................................................... 4
Properties and Uses of Esters ....................................................................................................................................................................... 4
Hydrolysis of Esters .......................................................................................................................................................................................... 5
Fatty Acids and Oils ........................................................................................................................................................................................... 5
Saponification ...................................................................................................................................................................................................... 5
Biodiesel ................................................................................................................................................................................................................. 6
Carboxylic Acid Derivatives .......................................................................................................................7
Acyl Chlorides ...................................................................................................................................................................................................... 7
Acid Anhydrides.................................................................................................................................................................................................. 7
Amides .................................................................................................................................................................................................................... 7
N-Substituted Amides ...................................................................................................................................................................................... 7
Acylation Reactions ........................................................................................................................................................................................... 7
Acylation ..................................................................................................................................................8
Nucleophilic Addition-Elimination ............................................................................................................................................................. 8
With Water ............................................................................................................................................................................................................. 8
With Alcohols ........................................................................................................................................................................................................ 8
With Ammonia ...................................................................................................................................................................................................... 8
With Primary Amines ........................................................................................................................................................................................ 8
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Aldehydes and Ketones
Carbonyl Group
• Aldehydes and ketones contain a carbonyl (C=O) group, which is highly polar.
• The δ+ carbon atom can be attacked by nucleophiles and undergo addition reactions, during which
the C=O bond is broken.
Oxidation of Alcohols
1° Alcohol + [O] ! Aldehyde + Water Acidified K2Cr2O7 (heat and distil)
Aldehyde + [O] ! Carboxylic Acid Acidified K2Cr2O7 or Tollen’s Reagent or
Fehling’s Solution (heat / reflux)
1° Alcohol + 2[O] ! Carboxylic Acid + Water Acidified K2Cr2O7 (heat / reflux)
2° Alcohol + [O] ! Ketone + Water Acidified K2Cr2O7 (heat / reflux)
(The acid used is typically H2SO4)
1° Alcohols:
• To oxidise a primary alcohol into an aldehyde as opposed to a carboxylic acid, remove the aldehyde
by distillation.
• Aldehydes have lower boiling points than equivalent alcohols as aldehydes lack hydrogen bonding.
Acidified Potassium Dichromate:
• Orange Cr2O72- ions are reduced to green Cr3+ ions when they oxidise a 1° alcohol, 2° alcohol or
aldehyde.
• Oxidation state of Cr changes from +6 to +3
Tollen’s Reagent:
• Contains [Ag(NH3)2]+ ions, which are reduced to a silver mirror when they oxidise an aldehyde into
a carboxylic acid.
• Oxidation state of Ag changes from +1 to 0.
• When added to an aldehyde, forms a silver mirror; when added to a ketone, no colour change occurs.
Fehling’s Solution:
• Blue Cu2+ ions are reduced to brick-red Cu2O when they oxidise an aldehyde into a carboxylic acid.
• Oxidation state of Cu changes from +2 to +1.
• When added to an aldehyde, a colour change from blue to brick-red occurs; when added to a ketone,
no precipitate forms.
Reduction of Carbonyls
Aldehyde + 2[H] ! 1° Alcohol Acidified NaBH4
Ketone + 2[H] ! 2° Alcohol Acidified NaBH4
Reducing Agent:
• NaBH4 is typically used as the reducing agent, but alternatively LiAlH4 can be used.
• LiAlH4 is a stronger reducing agent than NaBH4 and must be stored in dry ether as it reacts with
water (H2O removed by refluxing with Na).
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Aldehydes and Ketones
Nucleophilic Addition: Reduction of Carbonyls (Aldehyde/Ketone ! 1°/2° Alcohol)
Conditions: NaBH4 with dilute acid.
Reduction of Carbonyls Vs. Alkenes:
• Carbonyls can be reduced by nucleophilic addition or hydrogenation due to the polar C=O bond.
• Alkenes can only be reduced by hydrogenation (using H2 and a nickel catalyst at 150°C).
• Alkenes cannot be reduced by nucleophilic addition as they have no positive region for a nucleophile
to attack.
Nucleophilic Addition with :CN- (Carbonyl ! Hydroxynitrile)
Conditions: KCN / NaCN in water with dilute acid.
HCN:
• HCN provides a source of H+ ions and :CN- ions, however it is a very toxic gas, so is typically not
used.
KCN / NaCN:
• KCN and NaCN are not as poisonous as HCN and can provide CN- ions
• Acid must also be used to provide H+ ions.
• KCN is an irritant and is extremely dangerous if ingested of inhaled.
Hydroxynitriles:
• Nucleophilic addition using :CN- ions is particularly useful as it increases the carbon chain length.
• The nitrile group can be converted to a more useful carboxylic acid by hydrolysis using dilute acid.
Optical Isomerism in Hydroxynitrile Products:
• Reducing an aldehyde or an unsymmetrical ketone with acidified KCN will produce a mixture of
enantiomers.
• The carbonyl bond is planar, so there is an equal chance of the nucleophile attacking the δ+ carbon
from either above or below the plane of the carbonyl group.
• This will lead to a racemic mixture being produced if the product has a chiral centre.
Contents
Aldehydes and Ketones ........................................................................................................................ 2-3
Carbonyl Group ................................................................................................................................................................................................... 2
Oxidation of Alcohols ........................................................................................................................................................................................ 2
Reduction of Carbonyls.................................................................................................................................................................................... 2
Nucleophilic Addition ....................................................................................................................................................................................... 3
Reduction of Carbonyls ..................................................................................................................................................................................... 3
Addition of :CN- ..................................................................................................................................................................................................... 3
Esters ................................................................................................................................................... 4-6
Carboxylic Acids.................................................................................................................................................................................................. 4
Esters ....................................................................................................................................................................................................................... 4
Properties and Uses of Esters ....................................................................................................................................................................... 4
Hydrolysis of Esters .......................................................................................................................................................................................... 5
Fatty Acids and Oils ........................................................................................................................................................................................... 5
Saponification ...................................................................................................................................................................................................... 5
Biodiesel ................................................................................................................................................................................................................. 6
Carboxylic Acid Derivatives .......................................................................................................................7
Acyl Chlorides ...................................................................................................................................................................................................... 7
Acid Anhydrides.................................................................................................................................................................................................. 7
Amides .................................................................................................................................................................................................................... 7
N-Substituted Amides ...................................................................................................................................................................................... 7
Acylation Reactions ........................................................................................................................................................................................... 7
Acylation ..................................................................................................................................................8
Nucleophilic Addition-Elimination ............................................................................................................................................................. 8
With Water ............................................................................................................................................................................................................. 8
With Alcohols ........................................................................................................................................................................................................ 8
With Ammonia ...................................................................................................................................................................................................... 8
With Primary Amines ........................................................................................................................................................................................ 8
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Aldehydes and Ketones
Carbonyl Group
• Aldehydes and ketones contain a carbonyl (C=O) group, which is highly polar.
• The δ+ carbon atom can be attacked by nucleophiles and undergo addition reactions, during which
the C=O bond is broken.
Oxidation of Alcohols
1° Alcohol + [O] ! Aldehyde + Water Acidified K2Cr2O7 (heat and distil)
Aldehyde + [O] ! Carboxylic Acid Acidified K2Cr2O7 or Tollen’s Reagent or
Fehling’s Solution (heat / reflux)
1° Alcohol + 2[O] ! Carboxylic Acid + Water Acidified K2Cr2O7 (heat / reflux)
2° Alcohol + [O] ! Ketone + Water Acidified K2Cr2O7 (heat / reflux)
(The acid used is typically H2SO4)
1° Alcohols:
• To oxidise a primary alcohol into an aldehyde as opposed to a carboxylic acid, remove the aldehyde
by distillation.
• Aldehydes have lower boiling points than equivalent alcohols as aldehydes lack hydrogen bonding.
Acidified Potassium Dichromate:
• Orange Cr2O72- ions are reduced to green Cr3+ ions when they oxidise a 1° alcohol, 2° alcohol or
aldehyde.
• Oxidation state of Cr changes from +6 to +3
Tollen’s Reagent:
• Contains [Ag(NH3)2]+ ions, which are reduced to a silver mirror when they oxidise an aldehyde into
a carboxylic acid.
• Oxidation state of Ag changes from +1 to 0.
• When added to an aldehyde, forms a silver mirror; when added to a ketone, no colour change occurs.
Fehling’s Solution:
• Blue Cu2+ ions are reduced to brick-red Cu2O when they oxidise an aldehyde into a carboxylic acid.
• Oxidation state of Cu changes from +2 to +1.
• When added to an aldehyde, a colour change from blue to brick-red occurs; when added to a ketone,
no precipitate forms.
Reduction of Carbonyls
Aldehyde + 2[H] ! 1° Alcohol Acidified NaBH4
Ketone + 2[H] ! 2° Alcohol Acidified NaBH4
Reducing Agent:
• NaBH4 is typically used as the reducing agent, but alternatively LiAlH4 can be used.
• LiAlH4 is a stronger reducing agent than NaBH4 and must be stored in dry ether as it reacts with
water (H2O removed by refluxing with Na).
, 3
Aldehydes and Ketones
Nucleophilic Addition: Reduction of Carbonyls (Aldehyde/Ketone ! 1°/2° Alcohol)
Conditions: NaBH4 with dilute acid.
Reduction of Carbonyls Vs. Alkenes:
• Carbonyls can be reduced by nucleophilic addition or hydrogenation due to the polar C=O bond.
• Alkenes can only be reduced by hydrogenation (using H2 and a nickel catalyst at 150°C).
• Alkenes cannot be reduced by nucleophilic addition as they have no positive region for a nucleophile
to attack.
Nucleophilic Addition with :CN- (Carbonyl ! Hydroxynitrile)
Conditions: KCN / NaCN in water with dilute acid.
HCN:
• HCN provides a source of H+ ions and :CN- ions, however it is a very toxic gas, so is typically not
used.
KCN / NaCN:
• KCN and NaCN are not as poisonous as HCN and can provide CN- ions
• Acid must also be used to provide H+ ions.
• KCN is an irritant and is extremely dangerous if ingested of inhaled.
Hydroxynitriles:
• Nucleophilic addition using :CN- ions is particularly useful as it increases the carbon chain length.
• The nitrile group can be converted to a more useful carboxylic acid by hydrolysis using dilute acid.
Optical Isomerism in Hydroxynitrile Products:
• Reducing an aldehyde or an unsymmetrical ketone with acidified KCN will produce a mixture of
enantiomers.
• The carbonyl bond is planar, so there is an equal chance of the nucleophile attacking the δ+ carbon
from either above or below the plane of the carbonyl group.
• This will lead to a racemic mixture being produced if the product has a chiral centre.
