Summary Aldehydes and Ketones Notes - AQA Chemistry A Level

Aldehydes and Ketones
 Aldehydes contain a carbonyl group at the end of the carbon chain and are
formed from the oxidation of primary alcohols
o Readily oxidise further in the presence of acidified potassium
dichromate to form carboxylic acids
o Tested for using Tollen’s reagent or Fehling’s solution
 Ketones contain a carbonyl group within the carbon chain and are formed
from the oxidation of secondary alcohols
o No further oxidation and have no visible change with Tollen’s reagent
or Fehling’s solution

Reduction
 Aqueous NaBH4
 The NaBH4 is a source of hydride (H- ions) whilst the water provides H+ ions




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Addition of HCN
 KCN followed by dilute acid (source of H +)
 Aqueous conditions
 HCN does not disassociate easily so not a good source of CN - ions
o Is also hard to store as a gas and reacts to form dangerous byproducts
 Produces hydroxynitriles




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