Esterificaton

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Structure of an Ester

What is Esterification?

Esterification of Ethanoic Acid

Esterification of Ethanoyl Chloride

Uses of Esters

Synthesis of an Ester

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Formation of an Ester from Ethanoic Acid

Above shows the equation for the formation of an ester from ethanoic acid and an alcohol, this reaction also requires an acid catalyst (normally H₂SO₄ or HCl). The purpose of the acid catalyst is to increase the polarity of the C=O bond so the carbon end becomes slightly more positive, making it easier for the alcohol to attack it, leading to the formation of the ester. During the formation of an ester from an acyl chloride, no acid catalyst is need as the Cl atom is a much better leaving group (see the section on esterification of acyl chloride).

This diagram shows the mechanism for the formation of an ester from a carboxylic acid, the role of the acid catalyst can be clearly seen. Note how the H⁺ comes from H₃O⁺ not from H₂SO₄, the reasoning for this is simple - when an acid is added to water, the H⁺ will be taken on by water molecules, and SO₄^2- ions will be left in solution, if you would like to know more about this I would recommend looking on the internet or in a text book for "acid in solution"