COOH and esters Flashcards
How can COOH produce CO2
Carboxylic acids are weak acids but will liberate CO2 from carbonates.
This means they PARTIALLY DISSOCIATE to form a H+ ions and a carboxylate ion and so EQUILIBRIUM SHIFTS TO THE LEFT.
COOH + carbonate –> salt + co2 + water
EXAMPLE:
2CH3COOH + CO3^2- –> 2CH3COONa + CO2 + H2O
Organic Synthesis: Esterification
COOH + alcohol –> ester
(requires conc H2SO4)
to name an ester: name alcohol (eg methyl, ethyl, propyl) then the acid (eg methanoate, ethanoate, propanoate)
How are esters used commercial and industrial process
Perfumes/Food Flavourings: some esters have a sweet smell
Solvents: esters are polar so other polar molecules can DISSOLVE EASILY. Has LOW BP + evaporate easily –> used to make glues.
Plasticisers: esters used to make plastics more flexible during polymerisation (condensation polymers). They can leach out and the plastic becomes brittle.
Acid hydrolysis of esters
Add water + dilute HCl/sulfuric acid catalyst under REFLUX to produce an ALCOHOL + COOH
Adding more water shifts equilibrium to the right, SO MORE PRODUCTS.
Base hydrolysis of esters - saponification
Use a dilute base (NaOH)) under reflux
produces a carboxylate ion and an alcohol
ester + alkali
salt of carboxylate ion + alcohol
Give content about Oil/Vegetable Oil.
Oil is an ester.
Veg Oil:
*unsaturated C-H chains that ARE NOT STRAIGHT
*therefore chains can’t pack closely together.
*hence they have lower vdw forces
*has low melting points –> are liquids at room temp.
Give content about Fats/Animal Fats
*has saturated C-H chains that ARE STRAIGHT
*therefore can pack closely together
*hence they have stronger vdw forces than oils
*has higher melting points –> solids at room temp
Vegetable oils and animal fats can be hydrolysed in ALKALINE conditions to give soap + glycerol. How?
How to make biodiesel?
Biodiesel is a mixture of methyl esters of long-chain carboxylic acids.
Biodiesel is produced by reacting vegetable oils with methanol in the presence of a catalyst like KOH.
