AQA A-Level Chemistry: Esters

Vocabulary practice flashcards covering ester structure, nomenclature, intermolecular forces, formation, acidic and alkaline hydrolysis, and practical uses based on the AQA A-Level Chemistry specification.

Ester

A carboxylic acid derivative with the general formula $\text{R-COO-R}'$, where the hydrogen of the carboxylic acid group is replaced by an alkyl chain.

Esterification

A reversible reaction at dynamic equilibrium where a carboxylic acid and an alcohol react in the presence of an acid catalyst to produce an ester and water.

Condensation reaction

The broader, general term for a reaction such as esterification, in which two molecules join together with the release of a small molecule like water.

Acid hydrolysis of an ester

A reversible reaction where an ester is broken down by water using a dilute $\text{HCl}$ catalyst heated under reflux to form a carboxylic acid and an alcohol.

Saponification

The alkaline hydrolysis of an ester using dilute sodium hydroxide ($\text{NaOH}$) heated under reflux, which is non-reversible and yields a carboxylate salt and an alcohol.

Carboxylate salt

A negatively charged salt (e.g., sodium ethanoate, $\text{CH}_3\text{COO}^-\text{Na}^+$) produced by alkaline hydrolysis that cannot be attacked by weak nucleophiles like alcohols, making the reaction irreversible.

Sulfuric acid ($\text{H}_2\text{SO}_4$)

The concentrated acid catalyst utilized in esterification reactions to speed up the slow rate of reaction without changing the overall product yield.

Heat under reflux

The standard reaction condition required for esterification, acid hydrolysis, and alkaline hydrolysis of esters.

Plasticizer

A substance added to rigid, pure polymers to increase flexibility by reducing the intermolecular forces between polymer chains.

Volatile

A property describing a substance that readily turns into a gas or vapor, which is an essential requirement for esters used in perfumes.

Dynamic equilibrium

A state in an esterification reaction in which the forward and reverse reactions proceed at the exact same rate.

Intermolecular forces in esters

Forces that are weaker than those in carboxylic acids and alcohols (resulting in lower boiling points) because ester molecules cannot form hydrogen bonds with each other.