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4.8.4Unit 4. Rates, Equilibria and Further Organic Chemistry

Acyl Chlorides and Esters — IAL Edexcel Linear (Chemistry) Revision Notes & Topical Questions

5 min read 4 parts Lesson 48 of 56 Unit quiz

📚 IAL Edexcel Linear (Chemistry) Hub / Topical Revision
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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.
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Part 1 of 4Acyl Chlorides

Acyl chlorides have the functional group –COCl and are far more reactive than carboxylic acids.

Structure
  • Structure The carbon of the –COCl group is bonded to oxygen and chlorine, making it strongly δ⁺ and easily attacked.
Naming
  • Naming Names end in -oyl chloride, for example ethanoyl chloride, CH₃COCl.
Reaction type
  • Reaction type They react by nucleophilic addition–elimination, with the nucleophile adding and HCl then being lost.
Preparation
  • Preparation Carboxylic acids are converted to acyl chlorides by PCl₅ or by SOCl₂ (thionyl chloride).
Why so reactive
  • Why so reactive Chlorine is a good leaving group and the carbonyl carbon carries a strong partial positive charge,
    • so reaction needs no catalyst or heating.

Part 2 of 4Reactions of Ethanoyl Chloride

Each reaction is vigorous and occurs at room temperature, releasing fumes of hydrogen chloride.

Reactions of Ethanoyl Chloride
Water
  • Water CH₃COCl + H₂O → CH₃COOH + HCl gives ethanoic acid and steamy fumes of HCl.
Alcohol
  • Alcohol CH₃COCl + C₂H₅OH → CH₃COOC₂H₅ + HCl forms the ester ethyl ethanoate irreversibly.
Ammonia
  • Ammonia CH₃COCl + 2NH₃ → CH₃CONH₂ + NH₄Cl gives an amide and ammonium chloride.
Primary amine
  • Primary amine CH₃COCl + 2CH₃NH₂ → CH₃CONHCH₃ + CH₃NH₃Cl forms an N-substituted amide.

Part 3 of 4Esters

1
An ester is named from the alcohol part first and the acid part second, so C₂H₅OOCCH₃ is ethyl ethanoate.
2
Esters are made from a carboxylic acid and an alcohol with an acid catalyst, but this reaction is reversible.
3
Acyl chlorides give a better yield because the reaction goes to completion and does not reach equilibrium.
4
Esters are volatile, have pleasant smells, and are used as solvents, perfumes and food flavourings.

Part 4 of 4Exam Checklist & Tips

4.8.4 – Key Points for the Exam

  • Acyl chloride Compound containing –COCl.
  • Ester Compound containing –COO– between two carbon chains.
  • Addition–elimination Nucleophilic attack followed by loss of a small molecule.
  • Amide Compound containing –CONH–.

Common Mistakes

  • Naming the esters with the acid first, such as ethanoate ethyl.
  • Writing only one mole of ammonia in the amide reaction.
  • Saying acyl chlorides are less reactive than carboxylic acids.
  • Forgetting HCl is produced in each reaction.

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