9701 · 33.2
Esters flashcards
Revision flashcards for Cambridge 9701 Esters (syllabus 33.2). Flip, recall, then mark a real past-paper question.
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What is the functional group of an ester?
The ester functional group is –COO–, sometimes written as –COOR where R is an alkyl group.
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What are the reactants for esterification?
A carboxylic acid and an alcohol.
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What are the conditions for laboratory esterification?
Heat under reflux with a concentrated strong acid catalyst, typically sulfuric acid (H₂SO₄).
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What is the role of concentrated H₂SO₄ in esterification?
It acts as a catalyst to speed up the reaction and as a dehydrating agent to absorb the water produced, shifting the equilibrium to the right to favour the ester.
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How do you name an ester?
The first part of the name comes from the alkyl group of the alcohol. The second part comes from the name of the carboxylic acid, with the '-oic acid' ending changed to '-oate'.
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What is hydrolysis?
The breakdown of a compound by reaction with water. For esters, this splits the ester link.
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What are the products of acid hydrolysis of an ester?
A carboxylic acid and an alcohol. The reaction is reversible.
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What is saponification?
The alkaline hydrolysis of an ester. It is an irreversible reaction.
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What are the products of alkaline hydrolysis of propyl ethanoate?
Sodium ethanoate (a carboxylate salt) and propan-1-ol (an alcohol), assuming NaOH was the alkali used.
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Why is alkaline hydrolysis of an ester irreversible?
The carboxylic acid produced reacts immediately with the excess alkali to form a carboxylate salt. The carboxylate anion is resonance-stabilised and shows no tendency to react with the alcohol.
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What is a polyester?
A condensation polymer in which the monomer units are linked by ester functional groups.
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What monomers are used to make the polyester Terylene (PET)?
Benzene-1,4-dicarboxylic acid and ethane-1,2-diol.