Fischer esterification is an acid-catalyzed reaction between a carboxylic acid and an alcohol to form an ester and water. In the synthesis of ethyl acetate, acetic acid CH3COOH reacts with ethanol CH3CH2OH to form ethyl acetate CH3COOCH2CH3 and water H2O .The reaction mechanism for Fischer esterification involves several steps:1. Protonation of the carbonyl oxygen: The acid catalyst usually a strong acid like sulfuric acid, H2SO4 donates a proton H+ to the carbonyl oxygen of the carboxylic acid, making it more electrophilic. CH3COOH + H+ CH3C OH O+H2. Nucleophilic attack by the alcohol: The oxygen atom of the alcohol ethanol acts as a nucleophile and attacks the electrophilic carbonyl carbon, forming a tetrahedral intermediate. CH3C OH O+H + CH3CH2OH CH3C OH OCH2CH3 O+H3. Deprotonation of the tetrahedral intermediate: The positively charged oxygen atom in the tetrahedral intermediate loses a proton H+ to stabilize the molecule. CH3C OH OCH2CH3 O+H CH3C OH 2OCH2CH3 + H+4. Protonation of the hydroxyl group: The hydroxyl group OH in the intermediate gets protonated by the acid catalyst. CH3C OH 2OCH2CH3 + H+ CH3C OH OH2+ OCH2CH35. Elimination of water: The protonated hydroxyl group leaves as a water molecule, forming a carbocation intermediate. CH3C OH OH2+ OCH2CH3 CH3CO+OCH2CH3 + H2O6. Deprotonation of the carbocation: The carbocation intermediate loses a proton H+ to form the final ester product, ethyl acetate, and regenerates the acid catalyst. CH3CO+OCH2CH3 + H2O CH3COOCH2CH3 + H+The key intermediate in this reaction mechanism is the tetrahedral intermediate CH3C OH OCH2CH3 O+H . The reaction is in equilibrium, and the position of the equilibrium can be shifted towards the ester product by using an excess of one of the reactants usually the alcohol or by removing water from the reaction mixture.