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Imine formation using an aldehyde/ketone and primary amine is acid-catalyzed, yet the rate drops below pH 4.5. Why does the rate drop below this pH?
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The correct answer is:
Protonation of the amine decreases its nucleophilicity
Imine formation:
The reaction is possible pH 4 to 5 only. Hence, the reaction is pH dependent.
At very low pH (high conc. of ): ammonia derivative will form their respective salts due to their basic nature and at the same time will lose their nucleophilic nature.
At very high pH (high conc. of ): carbonyl group will not be able to undergo sufficient protonation.
The reaction is possible pH 4 to 5 only. Hence, the reaction is pH dependent.
At very low pH (high conc. of ): ammonia derivative will form their respective salts due to their basic nature and at the same time will lose their nucleophilic nature.
At very high pH (high conc. of ): carbonyl group will not be able to undergo sufficient protonation.
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