Bondline / Reactions

Ester hydrolysis (saponification)

Hydroxide adds to the ester C=O to form a tetrahedral intermediate, which collapses and expels the alkoxide. The final proton transfer makes the reaction irreversible.

Acyl substitution · 3 steps

Conditions

NaOH(aq), heat, then acidify to obtain the carboxylic acid.

Mechanism in 3 steps

Red curly arrows show where each pair of electrons moves.

HO−OOOO−OH+
Step 1Hydroxide adds to the carbonyl carbon, forming a tetrahedral intermediate.
OO−OHOHOO−+
Step 2The C=O reforms and methoxide is expelled.
OHOO−OO−OH++
Step 3Methoxide removes the acidic proton: carboxylate and methanol. This step is irreversible.

About acyl substitution reactions

Carboxylic acid derivatives react by nucleophilic addition followed by elimination: the nucleophile adds to C=O, then the leaving group is expelled and the C=O reforms.

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