Unit 4.4 Aldehydes and Ketones
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What can oxidising primary/secondary alcohols give u?
Aldehydes or ketones
What’s the oxidising agent used for the oxidisation of primary/secondary alcohols? (Either one)
• Acidified potassium dichromate (VI) • Acidified potassium manganate (VII)
Which alcohol being oxidised creates the formation of an aldehyde?
Primary alcohols
Show me the equation of the formation of an aldehyde from the oxidisation of primary alcohols (Whiteboard needed)
Where’s your whiteboard?
Which alcohol being oxidised creates the formation of a ketone?
Secondary alcohols
Show me the equation of the formation of a ketone from the oxidisation of secondary alcohols (Whiteboard needed)
Where’s your whiteboard?
What are the 2 reagents used to distinguish between aldehydes and ketones
• Tollen’s reagent • Fehling’s reagent
What consists of Tollen’s reagent? (2 things + 1 what?)
• Mild oxidising agents such as Ag+ • Usually an ammoniacal solution of silver nitrate • contains diamminesilver(I) ion, [(NH302Ag]+)
What does Tollen’s reagent oxidise?
The aldehyde
What observations are there from aldehyde with Tollen’s reagent? and how?
• Silver mirror forms • Oxidised further
What does Tollen’s reagent not oxidise?
The ketone
What observations are there from ketone with Tollen’s reagent? and how?
• No observable change or goes black • Cannot be oxidised further
Equation for aldehyde with Tollen’s reagent?
Get your whiteboard Carboxylic acid formed i think
Equation for ketone with Tollen’s reagent?
It don’t work
What is step 1 of Tollen’s reagent experiment (Method)
• Add 1cm (depth) of silver nitrate to a boiling tube
What is step 2 of Tollen’s reagent experiment (Method) (2-way)
• Add sodium hydroxide dropwise • until a brown ppt appears
What is step 3 of Tollen’s reagent experiment (Method) (2-way)
• Add ammonia (ammonium hydroxide) • until the brown ppt disappears
What is step 4 of Tollen’s reagent experiment (Method) (2-way)
• Add a squirt of glucose (aldehyde substitute) • to the mixture and warm in water bath
What consists of Fehling’s reagent?
2 solutions
What is solution A of Fehling’s reagent?
Aqueous copper(II) sulfate
What is solution B of Fehling’s reagent?
Sodium potassium tartrate (dissolved aq sodium hydroxide don’t listen to that part it’s wrong lol)
What does Fehling’s reagent oxidise?
The aldehyde
What observations are there from aldehyde with Fehling’s reagent?
Blue to brick-red
What does Fehling’s reagent not oxidise?
The ketone