9: Carboxylic Acids and Esters
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Describe dissociation of carboxylic acids.
Partially dissociate to H+ and carboxylate ion
Carboxylic acid + sodium carbonate produces…
Sodium carboxylate (salt) + water + CO2
Name 3 different strong acid catalysts that could be used in esterification reactions.
H2SO4 HCl H3PO4
If you heat a carboxylic acid with alcohol in the presence of a strong acid catalyst, what organic molecule is produced? What is the name of this reaction?
Ester, formed in esterification.
When reversing the reaction of carboxylic acid + alcohol = ester + water, what conditions are needed.
Reflux
How do we name esters?
Name the alcohol first, then the carboxylic acid.
How do we name benzene rings in esters?
Second in the name, benzoate
As esters smell sweet, what can they be used for?
Perfumes, food flavourings
Why are esters good solvents?
They are polar so other organic compounds will dissolve in them.
Esters can be used as plasticisers - how are they made?
Esters are added to plastics during polymerisation to make the plastic more flexible.
What is acid hydrolysis of esters?
Esters are split using a water and a dilute acid to an alcohol and carboxylic acid.
What conditions are needed for acid hydrolysis in the forward and backward reaction?
Forward - Dilute acid Backward - Reflux
Give a general equation for acid hydrolysis.
Ester + water = Carboxylic acid + alcohol
What conditions are needed for base hydrolysis?
Reflux and dilute alkali
What are the products of base hydrolysis?
Carboxylate ion and alcohol
What is the IUPAC name of glycerol?
propane-1,2,3-triol
Why are saturated fats solid at room temperature?
Saturated fats have no kinks in the chain. This allows the molecules to pack closer together increasing VDW force strength.
Why are oils liquids at room temperature?
They contain unsaturated chains, so molecules can’t pack as tightly together and therefore VDW forces are weaker.
What type of hydrolysis is used when splitting fats/oils?
Base
Base hydrolysis of fats produces what?
Glycerol and sodium salts
What are sodium salts used in?
Soaps
Give an equation for the conversion of sodium salts CH3(CH2)16COO-Na back into fatty acids CH3(CH2)16COOH
CH3(CH2)16COO-Na + H+ -> CH3(CH2)16COOH + Na+
Name the alkali usually used in base hydrolysis of fats.
NaOH
What must vegetable oils be reacted with under what conditions to produce biodiesels?
Methanol and strong alkali catalyst