Reductive Amination - Video Tutorials & Practice Problems

Reductive Amination

Hey guys. In this video, we're going to cook up a really important reaction called reductive amination. So guys, recall back to your ketones and aldehydes section of the text that ketones and aldehydes when reacted with a primary amine in an acidic environment, what would you get? You would get the functional group called an imine. Now what was an imine? Well, remember that an imine is just a carbonyl carbon but instead of the O being attached to the C, you're going to replace that O with an N. That N could be attached to up to 1 R groups. The reason that it can't be 2 R groups is because that would be called an enamine and the double bond would be in a different spot. We're not going to be talking about enamines here. We're only talking about imines. Well, guys, this mechanism was a reversible reaction. Remember that you have your double-sided equilibrium arrows showing that you can go from the carbonyl to the imine and then back to the carbonyl. But regardless of which direction y

Provide the Major Product

Alright, guys. So you might not have noticed, but this is one of the most famous applications of reductive amination. This is the Walter White special. This is how he made his millions. Remember that he didn't want to be making meth from pseudoephedrine anymore and he was looking for a more efficient type of cook. He really needed to find methylamine. Methylamine was his limiting reagent. Well, that's because he needed to do a reductive amination of methylamine, a primary amine source, with phenylacetone, which is a precursor for methamphetamine. Then all we need is methylamine at the top in an acidic environment. And then we need a mild reducing agent such as our sodium borohydride with the cyano group. That would work perfectly. Now he might have used some kind of H₂ gas with a catalyst, whatever. As long as you have some kind of mild reducing agent, you can reduce the iminium cation to the amine. So let's go ahead and draw both steps. I'm not going t