Esters
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What is an ester?
A derivative of carboxylic acids where the hydroxyl H is replaced with an alkyl group
What is esterification?
Making esters
How do we make esters from carboxylix acids?
Carboxylic acid + alcohol <—> ester + water Need c. H2SO4 catalyst and heat Methanoic acid + propan-1-ol HCOOH + CH3CH2COOH <–> HCOOCH2CH2CH3 + H20 (propyl methanoate)
How do we make an ester from acyl chloride?
Reacting with an alcohol —> ester + hydrogen chloride Eg ethanoyl chloride + methanol CH3COCl + CH3OH —> CH3COOCH3 + HCl (methyl ethanoate)
How do we make esters from acid anhydride?
React it with alcohol —> ester + carboxylic acid (CH3CO)2O + CH3CH2OH —> CH3COOCH2CH3 + CH3COOH (ethyl ethanoate and ethanoic acid)
What can esters be hydrolysed by?
Hot AQUEOUS acid or hot AQUEOUS alkali
What bond breaks when as ester is hydrolysed?
The sigma bond between the ester carbon and oxygen
Describe the acid hydrolysis of water.
React ester with water in presence of HOT ACID (H2SO4), making carboxylic acid and alcohol
What would happen in the acid hydrolysis of an ester? Give an example
Ester hydrolysed to carboxylic acid and alcohol. The acid doesn’t feature in the equation. HCOOCH2CH2CH3 + H2O <—> HCOOH + CH3CH2CH2OH
What would happen in the alkali hydrolysis od an ester? Give an example
Ester + metal hydroxide —> carboxylate salt + alcohol E.g : NaOH(aq) and propyl methanoate HCOOCH2CH2CH3 + NaOH —> HCOO-Na+ + CH3CH2CH2OH salt = sodium methanoate