Remember this is classed as an aldehyde as the carbonyl group is on the end of the chain not between 2 carbons
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Oxidising Aldehydes and Ketones
Aldehydes Oxidised to Carboxylic Acid
H attached to carbonyl group --> OH
Ketones cannot be reduced
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Tollens Reagent
Colourless solution of silver nitrate dissolved in NH₃ (aq)
When heated with an aldehyde Ag⁺ ions oxidised to Ag forming silver mirror
No reaction with Ketones as they aren't oxidised by Tollens
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Fehling's Solution
Blue solution of copper (ii) ions in NaOH
When heated with an aldehyde copper (ii) reduced to copper (i) oxide forming brick-precipitate
No reaction with Ketones
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Reducing Aldehydes and Ketones
Reduction from 2[H] (Reducing agent usually NaBH₄) dissolved in water with methanol
Aldehydes reduced to primary alcohols
Ketones reduced to secondary alcohols
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Mechanism
C (δ+) on Carbonyl attacked by H⁻ from [H]
Electrons from double bond go to O forming single bond between C and O⁻
H⁺ from water attracted to O⁻ and forms OH
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Reaction of carbonyl with KCN
Nucleophilic addition
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Mechanism
KCN dissociates in water to form K⁺ and CN⁻
CN⁻ attacks C (δ+) on carbonyl and bonds
Electrons from double bond on carbonyl go to O forming single bond between C and O⁻
H⁺ from water attracted to O⁻ and forms OH
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Risks of KCN
Irritant and extremely dangerous if inhaled or ingested
Can react with moisture to form HCN which is highly toxic
Gloves, safety goggles and a lab coat should be worn and a fume cupboard used
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Other cards in this set
Card 2
Front
R
|
R -- C == O
-one
Back
Ketone Functional Group
Card 3
Front
Methanal
Remember this is classed as an aldehyde as the carbonyl group is on the end of the chain not between 2 carbons
Back
Card 4
Front
Aldehydes Oxidised to Carboxylic Acid
H attached to carbonyl group --> OH
Ketones cannot be reduced
Back
Card 5
Front
Colourless solution of silver nitrate dissolved in NH₃ (aq)
When heated with an aldehyde Ag⁺ ions oxidised to Ag forming silver mirror
No reaction with Ketones as they aren't oxidised by Tollens
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