When reacting LiAlH4 with an amide, which should be used instead of the other in the final part of the reaction?

In the reaction of lithium aluminum hydride (LiAlH4) with an amide, the reduction of the amide typically produces either an amine or a different reduced product depending on the conditions. The reduction process first involves the formation of an intermediate, which then must be quenched to prevent further reaction.

Using H2O and H3O+ as the quenching agents is essential because, after the reaction with LiAlH4, you want to stabilize the product formed and also neutralize any remaining LiAlH4. LiAlH4 is a very strong reducing agent that can react with water, so using H2O to quench the reaction provides the necessary protons to neutralize LiAlH4, forming lithium hydroxide and ensuring that all the reducing agent is consumed before the final product is isolated.

The use of H3O+ specifically helps in protonating species in solution, thus ensuring that the final product is an amine rather than remaining as a less stable intermediate. This approach also allows for the solubility of the product in the aqueous phase and makes the work-up procedure straightforward.

In summary, H2O and H3O+ provide a safe and effective way to neutralize and stabilize the reaction