Base hydrolysis is a chemical reaction where a basic solution (high pH) causes a ligand to be replaced by a hydroxide (OH⁻) ion. This substitution reaction happens in the presence of a base, such as sodium hydroxide (NaOH).
Mechanisms of Base Hydrolysis
There are two primary mechanisms for base hydrolysis:
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Dissociative Mechanism: In this pathway, the leaving ligand departs before the hydroxide ion binds. This creates a transient intermediate with a reduced coordination number.
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Associative Mechanism: Here, the hydroxide ion binds to the central metal atom before the departure of the leaving ligand. This forms a higher-coordination number intermediate.
Examples of Base Hydrolysis
Base hydrolysis is common in various chemical reactions, including:
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Hydrolysis of Esters: In organic chemistry, esters undergo base hydrolysis (saponification) to produce carboxylic acids and alcohols. For example, the hydrolysis of ethyl acetate in the presence of sodium hydroxide yields acetic acid and ethanol.
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Hydrolysis of Metal Complexes: In coordination chemistry, many metal complexes undergo base hydrolysis, leading to the substitution of a ligand with a hydroxide ion. This alters the complex's properties.
The provided reference states that base hydrolysis "occurs when a reaction takes place in a basic medium, where a ligand is replaced by an OH- group. There are two mechanisms for base hydrolysis - dissociative and associative." This accurately summarizes the key aspects of this reaction type.
