And that difference gives chemists something extremely valuable: selectivity. Imagine mixing an aldehyde or ketone with an amine. They can temporarily form a C=N bond—an imine or iminium species. Now add sodium cyanoborohydride.
Under carefully controlled conditions, it preferentially reduces that C=N intermediate, turning the temporary connection into a stable C-N bond. The result? Two molecular fragments become one amine.
Global Chemical Database