ester hydrolysis

Question

Base-catalyzed ester hydrolysis (saponification) proceeds by initial:

RankGuru · Accepted Answer

1. **Mechanism type**: This is an **Acyl Nucleophilic Substitution ($B_{Ac}2$)**.
2. **Step 1**: The hydroxide ion ($OH^-$), acting as a powerful nucleophile, attacks the electrophilic carbonyl Carbon atom of the ester ($R-COOR'$).
3. **Intermediate**: This forms a **tetrahedral intermediate** where the carbonyl Carbon is now $sp^3$ hybridized.
4. **Step 2**: The tetrahedral intermediate collapses, reforming the $C=O$ double bond and expelling the alkoxide ion ($OR'^-$) as the leaving group.
5. **Step 3 (Irreversible)**: The resulting carboxylic acid immediately reacts with the hydroxide/alkoxide in the basic medium to form a carboxylate salt and an alcohol. This drive the reaction to completion.

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ester hydrolysis

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