7. Aldehydes & Ketones Flashcards
how can aldehydes be prepared - what reagents and reactants are needed
via PCC and primary alcohol
what are the 2 ways that ketones can be prepared
oxidation of alcohol
friedel craft acylation of aromatic ring
what reagents and reactants are needed when preparing ketones from alcohols via oxidation
H2CrO4 and secondary alcohol
what reagents and reactants are needed when preparing ketones via friedel craft acylation of aromatic ring
RXC=O/AlX3
what is tollens test in terms of reagents and reactants it involves and what it distinguishes between plus its observations
Ag(NH3)2+/heat
Ag+ ions reduced to form silver mirror for aldehydes and it produces COOH
no reaction or silver mirror for ketones - stays colourless
what is benedicts test in terms of reagents and reactants it involves and what it distinguishes between plus its observations
CuSO4/heat
blue to brick red colour change for aldehydes and COOH is produced
no colour change for ketone, stays blue
what is fehlings test in terms of reagents and reactants it involves and what it distinguishes between plus its observations
Cu2+ ions
blue to brick red precipitate for aldehydes
no reaction for ketones, stays blue
what reactants and reagents are needed when aldehydes are oxidised to COOH
H2CrO4
do ketones oxidise
no
what do you get when you oxidise aldehydes with H2CrO4
COOH
what reactants and reagents are needed when aldehydes and ketones are reduced to alcohols
NaBH4/H3O+
or
LiAlH4/H3O+
what do you get if you reduce an aldehyde with NaBH4/H3O+ or LiAlH4/H3O+
primary alcohol
what do you get if you reduce an ketone with NaBH4/H3O+ or LiAlH4/H3O+
secondary alcohol
what reagent and reactants do you need for aldehydes and ketones to react with grignards reagent
+RMgX
what do you get when methanal reacts with grignards reagent (+RMgX)
primary alcohol
what do you get when aldehyde reacts with grignards reagent (+RMgX)
secondary alcohol
what do you get when aldehydes and ketones reacts cyanide followed by H3O+
- CN- 2. H3O+
COOH
what reagents and reactants do you need to form a COOH from an aldehydes or ketone
- CN-
- H3O+
what are the 2 steps involved in nucleophillic addition of aldehydes or ketones for strong nucleophile
- +Nu-
- +H+
what are the 2 steps involved in nucleophillic addition of aldehydes or ketones for weak nucleophile
what other condition must be present for this to be possible
- +Nu-H
- -H+
must be where nucleophile is available in presence of an acid
for nucleophillic addition of aldehydes or ketones what is the rate limiting step
formation of Nu-
order these from fastest to slowest when udnergoing nucleophillic addition
aldehyde/methanal/ketone
why is there this difference in speed of reaction
methanal > aldehyde > ketone
due to increasing e- density with methanal progression to ketone (electronic and steric effects)
what reagents or reactants are needed for aldehydes and ketones to undergo addition of oxygen nucleophile to produce a hemiacetal and acetal
to form hemiacetal = +1ROH/H+
to form acetal = +2ROH/H+
what is produced when you react aldehydes or ketones with 1ROH/H+ and 2ROH/H+
1ROH/H+ = hemiacetal
2ROH/H+ = acetal
what is an acetal
has 2 OR groups on it
what is a hemiacetal
has -OR and -OH on it
what reagents are needed to produce a imine or hemiaminal when an alcohol undergoes addition of nitrogen nucleophiles
NH3 or RNH2
+RNH2 = prod hemiaminal
-H2O = prod imine
what is produced when you add NH3 or RNH2 to an alcohol
hemiaminal and then an imine
