6.1.2 & 6.1.3 - Carbonyls, Carboxylic acids, and Derivatives Flashcards
formula for aldehyde oxidation
aldehyde + [O] –> carboxylic acid
conditions for aldehyde oxidation
acidified potassium dichromate
heat under reflux
observations for oxidation of aldehydes
colour change: orange to green
can ketones be oxidised?
no
formula for the reduction of an aldehyde
aldehyde + 2[H] —> primary alcohol
formula for the reduction of an ketone
ketone + 2[H] –> secondary alcohol
conditions for reduction of ketones and aldehydes
H2O/NaBH4
by what mechanism do carbonyls reduce to alcohols
nucleophilic addition
examples of nucleophiles for reduction of carbonyls
H- (from NaBH4)
CN- (from HCN)
how do we make HCN
in situ with NaCN/H+
as HCN is a dangerous and poisonous liquid
2,4-DNP/ Brady’s reagent
Tests for the presence of a carbonyl group
C=O
positive test: yellow/ orange precipitate
how to identify the derivative after confirming the presence of a carbonyl group with Brady’s reagent
- purify derivative product by filtration and recrystallisation
- compare the melting point to known values to identify the compound
Tollen’s reagent
Tests for the presence of an aldehyde
positive test: silver mirror
what does tollen’s act as for an aldehyde
oxidising agent
equation for tollen’s with aldehyde
aldehyde + [O] –> carboxylic acid
Ag+(aq) + e- —> Ag(s) [reduced]
how to prepare tollen’s reagent
- CLEAN test tube
- add aqueous silver nitrate
- add aqueous sodium hydroxide until a brown precipitate (Ag2O) forms
- add dilute aqueous ammonia until the precipitate dissolves
how are carboxylic acids water soluble
contain polar C=O and O-H groups allowing them to form hydrogen bonds with water molecules
how does solubility of carboxylic acids change
longer carbon chain
less soluble carboxylic acid
test for carboxylic acids
react with a carbonate
effervescence
test the gas produced by bubbling through limewater
positive test: Turns cloudy (CO2)
esterification of COOH and alcohols
carboxylic acid + alcohol ⇌ ester + water
conditions for esterification of COOH and alcohols
concentrated strong acid catalyst (H2SO4)
heat
esterification of acid anhydride and alcohol
acid anhydride + alcohol –> ester + carboxylic acid
conditions for acid hydrolysis of esters
dilute strong acid (H2SO4)
reflux
equation for acid hydrolysis of esters
ester + water ⇌ carboxylic acid + alcohol
conditions for saponification (alkali hydrolysis)
reflux
aqueous hydroxide ions
equation for base hydrolysis of esters
ester + OH- –> carboxylate ion + alcohol
how can acyl chlorides be made from carboxylic acids
carboxylic acid + thionyl chloride –> acyl chloride + SO2(g) + HCL(g)
what is thionyl chloride
SOCl2
esterification of acyl chlorides
acyl chloride + alcohol –> ester + HCl
why doesnt the esterification of acyl chlorides and acid anhydrides require a catalyst
theyre more reactive than carboxylic acids
order of reactivity of COOH derivatives from least to most
RCOOH
acid anhydride
acyl chloride
why cant carboxylic acids undergo esterification with phenol
theyre not reactive enough
the equation for formation of carboxylic acids from acyl chlorides
acyl chloride + water –> carboxylic acid + HCl
