Carboxylic acids Flashcards
(25 cards)
functional group of carboxylic acid
COOH
general formula of carboxylic acid
CnH2n+1COOH
two polarised groups in carboxylic acids
C=O and O-H
why is the boiling points of carboxylic acids high
presence of OH bond can exhibit hydrogen bonding, lots of energy to overcome
why can carboxylic acids soluble
H bonding
why does solubility decrease as length of hydrocarbon chain increases
hydrocarbon chains force their way between water molecules, breaking hydrogen bonds between those water molecules
formation of carboxylic acids from primary alcohols oxidation
acidified potassium dichromate and reflux
potassium dichromate goes orange to green
orange chromate ions are reduced to green Cr3+ ions
hydrolysis of nitriles to make carboxylic acids
Propane nitrile + Hcl + H2O —> propanoic acid + ammonium chloride
the HCl is hydrolysed
can also work with Hydrolysis by dilute alkali resulting in the formation of a sodium carboxylate salt and ammonia; Acidification is required to change the carboxylate ion into a carboxylic acid
why are carboxylic acids weak acids
when in an aqueous solution they are only slightly ionized - giving low concentration hydronium ions and alkanoate ions
reactions that test for the presence of a carboxylic acid
Sodium carbonate: 2RCOOH + Na2CO3 → 2RCOO-Na+ + CO2 + H2O
Ionic equation with carbonates: 2RCOOH + CO32- → 2RCOO- + CO2 + H2O
Sodium hydrogen carbonate: RCOOH + NaHCO3 → RCOO-Na+ + CO2 + H2O
Ionic equation with hydrogen carbonates: RCOOH + HCO3- → RCOO- + CO2
because although carboxylic acids are weak, the concentration of hydrogen atoms is sufficient to react with a carbonate to produce co2
reduction of carboxylic acids reaction
LiAlH4 and dry ether
carboxylic acids are only reduced to primary alcohols or aldehydes
reaction of a carboxylc acid with metal oxides
metal salt and water are produced
eg. with magnesium oxide and ethanoic acid
magnesium ethanoate will form (CH3COO)2Mg
reaction of carboxylic acids with phosphorus chloride (PCl5)
forms an acyl chloride and POCl3
CH3CH2COOH (l) + PCl5 (s) → CH3CH2COCl (l) + POCl3 (l) + HCl (g)
steamy HCl fumes formed
reaction of carboxylic acids with alcohols
produces esters (COOR)
condensation reaction
H2SO4 catalyst
how to name ester
alcohol first word acid second
what is the reverse of esterification
hydrolysis
hydrolysis of esters reaction and conditions with an acid
heat under reflux
using sulfuric acid
produces carboxylic acid and alcohol
hydrolysis of esters reaction and conditions with an alkali
2 stage proccess
carboxylic acid reacts with excess alkali to form a carboxylate salt and alcohol
then add acid to this carboxylate salt to make it carboxylic acid (this protonates the molecule)
what is an acyl chloride
instead of carboxyilc acid the O-H is replaced with a chlorine
hydrolysis of acyl chlorides
forms carboxylic acid and HCl
addition of water
nucleophilic addition
formation of esters from acyl chlorides
react with alcohols
nucleophilic addition
HCl also formed
formation of amides from acyl chlorides
only with primary amines and concentrated ammonia
nitrogen in ammonia has lone pair
lone pair attacks the carbonyl carbon atom
HCl produced
what is condensation polymerisation
polymer produced by repeated condensation reactions between monomers
how is polyester formed
the reaction between dicarboxylic acid monomers and diol monomers
ester bonds link molecules up
water expelled in the condensation
