Simple aminoacetals hydrolyze quickly and easily in dilute aci...

Question

Simple aminoacetals hydrolyze quickly and easily in dilute acid. Propose a mechanism for hydrolysis of the following aminoacetal:

Mechanism of aminoacetal hydrolysis showing reactants, products, and hydronium ion in a chemical equation format.

Accepted Answer

All right. Hello everyone. So this question says that simple amino aces are hydrolyzed by dilute acids. What is the mechanism for the amino acetyl hydrolysis? Chan blo? So on the left side of the screen, here is our starting material, we have an al Coxie group and an amino group attached to the same carbon. And then when we look at the structures of the final products, we can see that both nitrogen and that amino acetal oxygen have been separated from the original carb that they were both attached to. And so that carbon has since become a carbonel to create an aldehyde in this case. And we also have an ammonium ion containing the same R groups as R amino group in the amino ace top. So here I went ahead and I briefly paused the recording just so I can go ahead and redraw the starting material. The fact that nitrogen is going to exist as a cion rather as an ammonium ion to be precise. That implies that the presence of acid in solution is going to proton, the nitrogen that we see in the amino acetal. This is because a proton nitrogen, if you recall makes for a better leaving group since it would become neutral after it detaches itself from carbon. So with this in mind, that's going to be our first step in the sequence. So here I already redrew the amino acetal. So now I am just going to go ahead and draw a hydro ion because from the hydro num ion, nitrogen is going to gain an additional proton. And so at this point, nitrogen has an additional proton and therefore a positive formal charge that makes it a better leaving group. And so now that we have a more suitable leaving group for this mechanism, it's the oxygen inside of the ring here from the amino acetal, that's going to help us detach nitrogen from carbon. And so one of the lone pairs of electrons on oxygen is going to establish a bond between oxygen aired the amino acetyl carbon. So that gives us a double bond and the nitrogen is displaced from that just to make sure that carbon doesn't have too many bonds at one time. However, in doing so, oxygen is now going to be positive, there is going to have a positive charge because of that extra bond to carbon, it only has one loan pair of electrons at this point. And so from here, the next step would be to go ahead and try and mitigate that positive charge that's on oxygen because oxygen being highly electron doesn't necessarily want to be positively charged right. So for this next step at this point, we're at step three, we have water, which is the conjugate base of the hydro of ion. So with that water in solution, water can go ahead and establish a new bond to that amino acetyl carbon that's now double bonded to the oxygen inside of the ring. And so that establishes a new bond between the oxygen of water and that carbon. And so that pi bond in between oxygen and carbon inside the ring goes back to oxygen making it neutral. Now, at this point, it's also worth mentioning that the oxygen that has now attached itself to carbon coming from that nucleic water molecule is going to be the carbon oxygen that we saw in the structures of the product. So here things are coming together. So now we have a single bond between the oxygen and carbon inside of the rings or inside of the rings singular. And now we have a proton water molecule branching off of the amino acetal carbon. And so from here, another water molecule is going to be necessary just to go ahead and detonate that oxygen. All right. So now water is going to react as a base here or an additional water molecule is going to react as a base. It's going to remove a proton from the oxygen that's currently positive. And so that gives oxygen an extra low impair to go ahead and make it neutral. And so at this point, our intermediate is no longer an amino acetal. At this point, we have a hemi aal because we have a hydroxy group and an oxy group attached to the same carbon. And so now our hay acetyl must break. Now, specifically the bond between carbon and the alcoy carbon, excuse me, carbon and the oxy oxygen must break. So these next few steps are going to do precisely that first, the alcoy oxygen is going to be pronated by an additional equivalent of hydro num. So here we have an extra hydro num ion and the oxy oxygen is going to take a proton from hydro. This means that the oxy oxygen is going to have a positive charge because of that additional bond to the new proton. And so that makes the oxy oxygen have a positive charge and therefore becomes a more suitable leaving group to break the bond between carbon and the oxy oxygen. And so, from here, in order to go ahead and encourage the separation of that bond between carbon and D oxy oxygen, the hydroxy oxygen from the oh group is going to establish a new double bond between itself and carbon by loaning a loan pair of electrons. This is what's going to break the bond between carbon and the oxy oxygen once again to make sure that carbon doesn't have too many bonds at one time. And so at this point, we have a proton needed car bono intermediate and we now have the neutral hydroxy group that we saw in the structures of the products at the very beginning of this video. And so the last step is just going to be a depot nation of that pronated car bono intermediate. So here we have an another water molecule behaving as a base and creating that neutral aldehyde group. And there you have it, this completes our total mechanism. And so with that being said, if you watch this video all the way through to the end, thank you so very much. And I hope you found this helpful.

Simple aminoacetals hydrolyze quickly and easily in dilute acid. Propose a mechanism for hydrolysis of the following aminoacetal:

Key Concepts

Aminoacetals

Hydrolysis Mechanism

Acid-Base Catalysis

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