Question #110666

A student attempts the one-pot reductive amination of benzaldehyde ($0.10\text{ M}$) with ethanamine ($0.10\text{ M}$) in an aqueous buffer at $\text{pH} = 4.0$ and $298\text{ K}$. To this mixture, $\ce{NaBH4}$ ($0.10\text{ M}$) is immediately added.

The hydrolysis of $\ce{NaBH4}$ in acidic media follows second-order kinetics: $-\frac{d[\ce{BH4^-}]}{dt} = k[\ce{H^+}][\ce{BH4^-}]$, where $k = 1.0 \times 10^6\text{ L mol}^{-1}\text{s}^{-1}$ at $298\text{ K}$. The hydrolysis reaction proceeds as follows:

\ce{BH4^- + H^+ + 3H2O -> H3BO3 + 4H2 ^}

Assuming the rate of imine reduction is negligible compared to hydrolysis under these conditions, determine the initial rate of $\ce{H2}$ gas evolution and the major organic species isolated after 10 minutes followed by a mild basic workup.