The reaction between a carboxylic acid and an alcohol to form an ester is called esterification. In this case, we will discuss the Fischer esterification mechanism, which involves the reaction between acetic acid and ethanol to form ethyl acetate. A catalyst, usually a strong acid like sulfuric acid H2SO4 , is used to facilitate the reaction.Here is a step-by-step explanation of the mechanism:1. Protonation of the carbonyl oxygen: The carbonyl oxygen of the acetic acid is protonated by the strong acid catalyst H2SO4 , making it more electrophilic and susceptible to nucleophilic attack. O=C-OH + H2SO4 O=C + -OH + HSO4 - 2. Nucleophilic attack: The lone pair of electrons on the oxygen of the alcohol ethanol attacks the electrophilic carbonyl carbon, forming a tetrahedral intermediate. O=C + -OH + CH3CH2OH O - -C + -OH + CH3CH2O-H3. Proton transfer: A proton from the protonated alcohol is transferred to one of the hydroxyl groups in the tetrahedral intermediate. O - -C + -OH + CH3CH2O-H O - -C-OH + CH3CH2O + -H4. Elimination of water: The hydroxyl group in the tetrahedral intermediate acts as a leaving group, and the electrons from the oxygen-carbon bond reform the carbonyl double bond, resulting in the elimination of water. O - -C-OH + CH3CH2O + -H O=C-O-CH2CH3 + H2O5. Deprotonation of the ester: The ester is deprotonated by the conjugate base of the acid catalyst HSO4- , regenerating the acid catalyst and forming the final ester product, ethyl acetate. O=C-O-CH2CH3 + HSO4 - O=C-O-CH2CH3 + H2SO4Overall reaction: CH3COOH acetic acid + CH3CH2OH ethanol CH3COOCH2CH3 ethyl acetate + H2O water The Fischer esterification mechanism is an equilibrium process, and the reaction can be driven to completion by using an excess of one of the reactants or by removing one of the products usually water from the reaction mixture.