The rate of imine formation from an aldehyde and a primary amine is greatest at about

ApH 1
BpH 10
CpH 4 to 5
DpH 14

Answer: C

Acid is needed to catalyse dehydration of the carbinolamine, but too much acid protonates the amine and removes its nucleophilicity. The compromise is a rate maximum near pH 4 to 5.

Practice Organic Reaction Mechanisms I: Nucleophiles and Carbonyl Addition More on Formation of acetals, imines and enamines

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