4.7.2Organic Chemistry
Practical: Preparation of Ethyl Ethanoate — Edexcel Linear - OL (Chemistry) Revision Notes & Topical Questions
5 min read 6 parts Lesson 17 of 18 Unit quiz
Curriculum Equation Key معادلة تفاعل تكوين الإستر (الأسترة) - Esterification Reaction EquationFast Exam Solution
R-COOH + R2-OH ⇌ (conc. H₂SO₄) R-COO-R2 + H₂O
Word Equation & Conditions: حمض كربوكسيلي + كحول (في وجود حمض الكبريتيك المركز كعامل حفاز ونازع للماء) ⇌ إستر + ماء
Location & Specifications: الكيمياء العضوية للثانوية العامة والتحصيلي و Edexcel Chemistry.
Part 1 of 6The Reaction
An alcohol and a carboxylic acid react to form an ester and water.
Equation
- Equation CH₃COOH + C₂H₅OH ⇌ CH₃COOC₂H₅ + H₂O, an esterification reaction.
Catalyst
- Catalyst A few drops of concentrated sulfuric acid act as the catalyst.
Reversible
- Reversible The reaction is reversible, so it does not go to completion unless the product is removed.
Ester
- Ester Ethyl ethanoate is a volatile ester with a sweet, fruity smell.
Part 2 of 6Method
Removing the ester as it forms prevents the reverse reaction.
1
Mix ethanoic acid, ethanol and a little concentrated sulfuric acid in a flask.
2
Warm the mixture gently using a water bath or electric heater, not a naked flame, because ethanol is flammable.
3
Distil the ester off as soon as it forms and collect it by condensation in a beaker.
4
Smell the distillate carefully to check for the fruity odour of an ester.
5
Add sodium carbonate solution until fizzing stops, to remove acidic impurities.
6
Add calcium chloride solution to remove leftover ethanol.
Part 3 of 6Why the Method Works
Why the Method Works
Low boiling point
- Low boiling point Esters are volatile and boil at lower temperatures than the acid, so they distil over first.
Le Chatelier
- Le Chatelier Removing the product shifts the equilibrium towards the ester, increasing yield.
Sodium carbonate
- Sodium carbonate It reacts with the acid impurities and produces carbon dioxide, so fizzing shows when they are removed.
Water bath
- Water bath A water bath avoids open flames and gives gentle, even heating.
| Substance | Role |
|---|---|
| Ethanoic acid | Carboxylic acid reactant |
| Ethanol | Alcohol reactant |
| Conc. sulfuric acid | Catalyst |
| Sodium carbonate | Neutralises acidic impurities |
Part 4 of 6Safety and Evaluation
Safety and Evaluation
Fire risk
- Fire risk Ethanol and the ester are flammable, so keep naked flames away.
Corrosive
- Corrosive Concentrated sulfuric acid and ethanoic acid are corrosive, so wear eye protection.
Yield
- Yield Percentage yield is less than 100% because of the reversible reaction and transfer losses.
Part 5 of 6Worked Example
Question
- 4.6 g of ethanol reacts with excess ethanoic acid and 5.3 g of ethyl ethanoate is obtained.
- Calculate the percentage yield.
- (Ar: C = 12, H = 1, O = 16)
- Mr of ethanol C₂H₅OH = 46, so moles = 4.6 ÷ 46 = 0.10 mol.
- One mole of ethanol gives one mole of ester, so theoretical moles of CH₃COOC₂H₅ = 0.10 mol.
- Mr of ethyl ethanoate C₄H₈O₂ = (4 × 12) + 8 + 32 = 88, so theoretical mass = 0.10 × 88 = 8.8 g.
- Percentage yield = 5.3 ÷ 8.8 × 100 = 60%.
Answer Percentage yield = 60% (to 2 s.f.)
Part 6 of 6Exam Checklist & Tips
4.7.2 – Key Points for the Exam
- Ester An organic compound with the –COO– linkage, formed from a carboxylic acid and an alcohol.
- Esterification The reaction of a carboxylic acid with an alcohol to make an ester.
- Distillation Separation of liquids by evaporation and condensation.
- Volatile Evaporating easily at low temperatures.
Common Mistakes
- Heating the flammable mixture with a Bunsen burner.
- Forgetting that the reaction is reversible and needs the ester removed.
- Using sulfuric acid as a reactant rather than as a catalyst.
- Adding sodium carbonate solution to the ester without waiting until the fizzing stops, leaving acid impurities.
Last updated:
\n