Esterification
Acid activation allows ethanol to add to benzoic acid; proton transfers and water loss produce ethyl benzoate. The aromatic ring stays intact throughout the acyl substitution.
- Reagents
- Ethanol; H2SO4 catalyst
- Conditions
- Warm with acid catalyst; the linked microscale procedure uses a water bath
- Reaction class
- Esterification
- Equation
- C6H5COOH + CH3CH2OH <=> C6H5COOCH2CH3 + H2O
Overview
Acid activation allows ethanol to add to benzoic acid; proton transfers and water loss produce ethyl benzoate. The aromatic ring stays intact throughout the acyl substitution.
Transformation
- Equation
- C6H5COOH + CH3CH2OH <=> C6H5COOCH2CH3 + H2O
- Reactants
- Benzoic acid + Ethanol
- Products
- Ethyl benzoate + Water
- Reagents
- Ethanol; H2SO4 catalyst
- Environment
- Warm with acid catalyst; the linked microscale procedure uses a water bath
- Reaction class
- Esterification
- Mechanism
- acid-catalysed nucleophilic acyl substitution
- Evidence level
- source-backed molecular example
Reference procedure
Microscale ethyl-benzoate formation
Benzoic acid + ethanol ⇌ ethyl benzoate + water
Materials and quantities
- Benzoic acid
- Ethanol
- Sulfuric-acid catalyst as specified in the source
Apparatus
- Reference microscale pipette apparatus
- Controlled water bath
Procedure
- Use the source’s benzoic-acid/ethanol mixture and catalyst in its prescribed microscale apparatus.
- Warm in the controlled water bath and cool before assessment.
Work-up and isolation
- This reference demonstrates ester formation without an isolation sequence or a validated percentage yield.
- For product identification, obtain chromatographic or spectroscopic evidence from a separately validated isolation method.
Critical controls
- The starting acyl compound is benzoic acid, not benzoyl chloride.
- Identify the product using its analytical measurements.
- Do not generalise the source’s small apparatus to a larger scale or an improvised sealed vessel.
Practical techniques
Controlled heating
Apply the stated temperature deliberately, using a heat source and vessel suited to the solvent, scale and required temperature rather than treating ‘heat’ as a complete procedure.
Setup
- Select the bath from the cited temperature: a water bath is limited to temperatures near 100 °C, while higher temperatures require an appropriate oil or sand bath or another specified heater.
- Clamp the vessel securely and position the temperature probe so it measures the reaction or bath consistently without touching the heater.
- Use a vented arrangement unless the cited method explicitly specifies pressure-rated equipment; ordinary glassware must not be improvised as a sealed reactor.
- Bring the mixture to the stated temperature gradually and start timing only after the working temperature is reached.
Operating checks
- Use electric heating rather than a naked flame for flammable organic solvents.
- Add anti-bumping granules before heating, not to a hot liquid.
- Do not infer a temperature, duration or scale when the source gives only the word ‘heat’; obtain the substrate-specific procedure first.
Scope and limitations
- Scope
- Benzoic acid supplies the aromatic acyl group; ethanol supplies the ethoxy group.
- Limitations
- This direct acid/alcohol equilibrium differs from benzoyl-chloride alcoholysis. Isolation and purity belong to the linked practical record.
Related reactions
- Side chain oxidation: Toluene → Benzoic acid
Toluene gives benzoic acid through side-chain oxidation.
- Complete oxidation: Benzyl alcohol → Benzoic acid
Oxidation first changes the benzylic CH2OH group into an aldehyde and then into carboxylate under the alkaline conditions. Acid work-up gives benzoic acid; the ring is retained while the side-chain carbon becomes more oxidised.
- Aldehyde oxidation: Benzaldehyde → Benzoic acid
Water reversibly adds to the aldehyde to form a hydrate, which can then be oxidised. The aldehyde carbon becomes the acid carbonyl carbon; acid work-up converts the initially formed benzoate into benzoic acid.
- Acyl chloride preparation: Benzoic acid → Benzoyl chloride
Reaction with phosphorus(V) chloride replaces the carboxyl OH group with chlorine, retaining the acyl carbon and aromatic ring. The new acyl chloride is more susceptible to nucleophilic substitution, while POCl3 and HCl account for the remaining atoms.
- Ester formation: Benzoyl chloride → Ethyl benzoate
Ethanol oxygen attacks the acyl carbonyl carbon. Loss of chloride and proton transfer restore C=O and form the ester, with ethanol contributing the ethoxy group and HCl produced in the overall equation.
References
- Microscale preparation of ethyl benzoateRoyal Society of Chemistry · RSC Education
Verified 2026-09-16 alongside the practical catalog. Supports benzoic acid and ethanol esterification; this is a different starting material from benzoyl chloride.
- Pearson Edexcel International Advanced Level Chemistry Student Practical GuidePearson Education Limited · Pearson qualifications · 2018
Supports the practical distinctions between reflux, distillation, liquid-liquid separation, washing and drying in organic preparations.