aldehydes and ketones 3.3.8 in papers 2 + 3
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what are carbonyls?
• a molecule with a c=o bond • either a ketone or aldehyde
how can you tell a molecule is an aldehyde or ketone?
• aldehydes c=o bond would be at the start or end of the molecule whereas in a ketone the bond would be somewhere in the middle
what do ketones and aldehydes oxidise to and what is the oxidising agent called?
• aldehydes oxidise to carboxylic acids • ketones dont oxidise • the oxidising agent is called pottasium dichromate (k2Cr2O7)
what are the functional group tests for aldehydes and their results?
• tollens reagent [Ag(NH3)2]+ silver mirror • fehlings solution (Cu2+) blue to red percipitate
what is the reducing agent for carbonyls and what are they reduced to?
• sodium tetrahydridoborate (NaBH4) • aldehyes reduce to primary alcohols • ketones reduce to secondary alcohols
why is NaBH4 attracted to the c=o bond?
contains :H-
what are the hazards of using KCN?
its toxic, due to the prescence of cynaide
what is formed when aldehydes and unsymetrical ketones react with KCN followed by a dilute acid?
• enantiomers, forming a racemate as it has a 50% chance of attacking both sides • hydroxy nitrile