Acyl chloride + alcohol → ester template

Ethanol attacks ethanoyl chloride, the tetrahedral intermediate expels chloride and loss of H⁺ gives ethyl ethanoate and HCl.

Mechanism step by step

Nucleophilic addition–elimination: the alcohol adds, chloride leaves, HCl is lost

1. Addition – The O lone pair attacks the C=O carbon
2. Elimination – C=O re-forms and chloride leaves
3. Deprotonation – Chloride takes H⁺: HCl

Key points

• Fast and irreversible at room temperature, with steamy fumes of HCl (unlike Fischer esterification).
• Reactivity: acyl chloride > anhydride > ester > amide, following the leaving group (Cl⁻ is the best).
• Water gives the carboxylic acid, NH₃ the amide, amines N-substituted amides, by the same mechanism.
• Pyridine or Et₃N is often added to mop up HCl; phenols, which barely react with acids, give esters this way.

Drawn with 57 atoms, 10 arrows, 9 shapes – every one editable in MolDraw.

Sources

• Clayden, Greeves & Warren, Organic Chemistry, 2nd ed., OUP 2012, ch. 10 Textbook
• Smith, March's Advanced Organic Chemistry, 8th ed., Wiley 2020, ch. 16 Textbook