Upper secondary · 15 min

Esterification: making ethyl acetate

Follow the atom-level rearrangement as acetic acid and ethanol form ethyl acetate and water in an acid-catalysed equilibrium.

Goal

Relate functional groups and bond changes to the Fischer esterification equation; understand that conversion is reversible and limited by equilibrium.

Apparatus and reagents

Acetic acid and ethanol, a few drops of concentrated sulfuric acid catalyst, reflux condenser, heating mantle or bath, boiling chips and goggles.

Procedure

Rotate the reactant arrangement at ξ = 0 and identify the carbonyl carbon, acid hydroxyl oxygen and ethanol oxygen.
Increase ξ in small increments. Track the alcohol oxygen forming a bond to the acyl carbon and the acid hydroxyl group becoming part of water.
At ξ = 1, check that the net products are ethyl acetate and water and that the atoms are conserved.
In a supervised real reflux experiment, compare equilibrium yield after changing reactant ratio or removing water; do not infer a rate or transition state from this interpolated animation.

What to observe

At ξ = 0 the acid C–OH bond is intact; as ξ increases the alcohol oxygen approaches the carbonyl carbon and a new C–O bond grows.
At ξ = 1 the acid OH and the alcohol H have combined into a separate water molecule; the ester C–O–C linkage remains.

Explanation

Fischer esterification is an equilibrium (K ≈ 4): acid loses OH, alcohol loses H (¹⁸O-labelling, Roberts & Urey 1938). Yield is pushed by excess alcohol or by removing water; the animation interpolates the net change — it is not a computed mechanism.

History of the experiment

The reaction was already described by Genth in 1848, but it was Emil Fischer who in 1895, with Arthur Speier, established the practical recipe: reflux the acid with excess alcohol in the presence of a strong acid catalyst. 'Fischer esterification' remains a first-year organic staple, and the equilibrium concept behind it fed directly into the nineteenth-century study of reversibility by Berthelot and Péan de Saint-Gilles.

Chemists behind it

Emil Fischer