The ketone shown is stirred with methylamine and sodium cyanoborohydride at pH about 5. Which structure is the major product?

AStructure A
BStructure B
CStructure C
DStructure D

Answer: C

Pentan-3-one condenses with the primary amine methylamine to form an imine (protonated to an iminium ion at this pH). Sodium cyanoborohydride reduces the iminium ion faster than the ketone, converting C=N to C-N: this is reductive amination, giving the secondary amine N-methylpentan-3-amine.

Practice Organic Reaction Mechanisms I: Nucleophiles and Carbonyl Addition More on Acetal, imine and enamine formation

Previous questionNext question

More questions on Acetal, imine and enamine formation

The aldehyde shown reacts with a primary amine to give an imine. Select the correct statement(s) about the pH dependence of the rate. JEE Advanced level
The meso diol shown reacts with benzaldehyde under acid catalysis to give a cyclic acetal (1,3-dioxolane) whose two ring stereocentres deriv... JEE Advanced level
The hydroxy aldehyde shown is dissolved in an excess of methanol containing a catalytic amount of dry HCl. Which structure is the major prod... JEE Advanced level
The keto aldehyde shown is treated with one equivalent of ethane-1,2-diol and an acid catalyst (water removed), then with sodium borohydride... JEE Advanced level
The enamine shown is alkylated with methyl iodide and the product is then hydrolysed with dilute aqueous acid (Stork enamine sequence). Whic... JEE Advanced level