Flashcards in 26 Deck (18):
How to oxidise an aldehyde?
Aldehyde + [O] = carboxylic acid
K2Cr2O7/H2SO4 catalyst, reflux
Why can't ketones undergo oxidation?
Lack of hydrogen
What reaction do ketones and aldehydes undergo?
Nucleophilic addition (polar C=O)
How to distinguish between an aldehyde and a ketone? (Reaction)
Tollen's reagent (silver nitrate solution in aqueous NH3) Ag+(aq) + e- = Ag(s)
An aldehyde would form a silver mirror
A ketone would not react because they cannot be oxidised
How to test for the carbonyl group?
Brady's reagent (2,4-dinitrophenylhydrazine)
Aldehyde/ketone + Brady's reagent = 2,4-dinitrophenylhydrazone
How to reduce an aldehyde?
Aldehyde + 2[H] = primary alcohol
How to reduce a ketone?
Ketone + 2[H] = secondary alcohol
Which carbonyl group has a higher boiling point?
Solubility of carboxylic acids
Soluble in water, C=O and O-H bonds are polar which forms hydrogen bonds (up to 4)
Solubility decreases as carbon chain increases
Carboxylic acid + metal
Carboxylate salt + H2
Carboxylic acid + base
Carboxylate salt + H2O (+ CO2 if carbonate base)
How to test for the carboxylate group?
React with a carbonate, observe effervescence
How to form an ester?
Carboxylic acid + alcohol = ester + H2O (esterification)
Acyl chloride + alcohol = ester + Hal
Acid anhydride + alcohol = ester + carboxylic acid
What is acid hydrolysis?
Reverse of esterification (heated under reflux)
Ester + H2O = carboxylic acid + alcohol
Dilute acid catalyst
What is alkaline hydrolysis?
Ester + OH- = carboxylate ion + alcohol (irreversible)
Preparation of acyl chlorides
Carboxylic acid + SOCl2 (thionyl chloride) = acyl chloride + SO2(g) + HCl(g)
Carried out in a fume cupboard
Forming carboxylic acids from acyl chlorides
Acyl chloride + H2O = carboxylic acid + HCl