Esterification
Carboxylic acids react with alcohols to form esters.
- Reagents
- alcohol
- Conditions
- concentrated H2SO4, heat under reflux
- Reaction class
- esterification
- Equation
- R-CO2H + R'OH <-> R-CO2R' + H2O
Overview
Carboxylic acids react with alcohols to form esters.
Transformation
- Equation
- R-CO2H + R'OH <-> R-CO2R' + H2O
- Reagents
- alcohol
- Environment
- concentrated H2SO4, heat under reflux
- Reaction class
- esterification
- Mechanism
- acid-catalysed esterification
- Evidence level
- textbook core
Reference procedure
Microscale reference: ester formation
Ethanoic acid + ethanol → ethyl ethanoate
Materials and quantities
- Ethanoic acid — 10 drops
- Ethanol — 10 drops
- Concentrated sulfuric acid — 1 drop in the specimen tube
- Water — about 10 cm³ for the heating bath
- Sodium carbonate solution — 0.5 mol dm⁻³, half a test tube for work-up
Apparatus
- Borosilicate specimen tube
- Dropping pipettes
- 100–250 cm³ beaker for a hot-water bath
- Test tube and rack
- Tongs and eye protection
Procedure
- Add the ethanoic acid to the sulfuric acid in the specimen tube, then add the ethanol.
- Stand the tube upright in a beaker containing about 10 cm³ of water. Heat gently until the water begins to boil, then stop heating.
- Leave the reaction tube in the hot water for 1 minute, removing it briefly with tongs if the reaction mixture itself starts to boil.
- Allow the tube to cool before beginning the carbonate work-up.
Work-up and isolation
- Pour the cooled mixture into a test tube half-full of 0.5 mol dm⁻³ sodium carbonate solution.
- Mix carefully; effervescence occurs while residual acids are neutralised.
- Allow the ester layer to separate. This microscale method does not produce enough purified material for a yield or boiling-point determination.
Critical controls
- Use eye protection and handle concentrated sulfuric acid and ethanoic acid as corrosive reagents.
- Use a water bath rather than a naked flame around the flammable alcohol and ester.
- Do not smell directly from the tube; if odour is assessed, waft vapour only after the carbonate work-up.
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
- Carboxylic acids and alcohols form esters under acid-catalysed reflux.
- Limitations
- Equilibrium position and work-up are not shown in the route graph.
Related reactions
- Oxidation: Alcohols → Carboxylic acids
Full oxidation of a primary alcohol gives a carboxylic acid.
- Complete oxidation: Primary alcohols → Carboxylic acids
Full oxidation of a primary alcohol gives a carboxylic acid.
- Reduction: Carboxylic acids → Primary alcohols
Reduction of a carboxylic acid gives a primary alcohol.
- Oxidation: Aldehydes → Carboxylic acids
Oxidation of an aldehyde gives a carboxylic acid.
- Hydrolysis: Nitriles → Carboxylic acids
Nitriles can be hydrolysed to carboxylic acids, splitting the old aggregate nitrile-to-amide route into a single functional-group conversion.
- Activation for amide formation: Carboxylic acids → Amide chemistry
Carboxylic acids or activated acid derivatives connect to amide-bond formation.
- Esterification co reactant: Alcohols → Esters
Alcohols combine with carboxylic acids to form esters.
- Hydrolysis: Esters → Carboxylic acids
Hydrolysis converts esters back into carboxylic acid products.
- Hydrolysis co product: Esters → Alcohols
Hydrolysis of an ester also regenerates the alcohol component.
- Chlorination: Carboxylic acids → Acyl chlorides
PCl5 converts carboxylic acids into acyl chlorides.
- Chlorination with thionyl chloride: Carboxylic acids → Acyl chlorides
Thionyl chloride converts carboxylic acids into acyl chlorides with sulfur dioxide and hydrogen chloride as by-products.
- Hydrolysis: Acyl chlorides → Carboxylic acids
Water hydrolyses acyl chlorides to carboxylic acids, releasing hydrogen chloride.
- Acylation: Acyl chlorides → Esters
Alcohol acylation converts acyl chlorides into esters.
- Carboxylation: Grignard reagents → Carboxylic acids
Grignard carboxylation gives carboxylic acids after acidic work-up.
- Grignard carboxylation co reactant: Carbon dioxide → Carboxylic acids
Carbon dioxide plus a Grignard reagent gives a carboxylic acid after acidic work-up.
- Salt formation: Carboxylic acids → Carboxylate salts
Carboxylic acids react with bases, carbonates and reactive metals to form carboxylate salts.
References
- Pearson Edexcel Level 3 Advanced GCE in Chemistry specificationPearson Education Limited · Pearson qualifications · 2024
Supports the textbook-core organic reaction routes used for displayed route and mechanism content.
- Making esters from alcohols and acidsRoyal Society of Chemistry and Nuffield Foundation · RSC Education
Provides a microscale esterification method, quantities, hot-water heating and carbonate work-up; it is a characterisation-scale rather than yield-scale preparation.
- 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.