Propose mechanisms for the three imine-forming reactions just ...

Question

Propose mechanisms for the three imine-forming reactions just shown.

Accepted Answer

Hi, everyone. Welcome to the next video. Let's look at our next problem, propose a suitable mechanism to show the IMing formation in the given reaction and were given a six carbon ring with a carbon group. So a ketone and it's under acidic conditions reacting with H 30 plus and fennel amine. So a fennel ring with an NH two group on it to form the mean which is a six carbon ring. But instead of our carbon eel group C double bonded to an O, it's now an M NG C double bonded to the N with that fennel group attached. So Aldo hides and ketones in acidic conditions do react with a means through a condensation reaction. So elimination of a small molecules such as water or alcohol to form, it means the C O double bond replaced with the C N double bond. So as we look at our mechanism, we're going to start with an acid catalyzed nuclear filic edition of the, aiming to the Carbondale group. So we're gonna break that C O double bond um through the addition of a proton and we're then going to have that Amin attack our residents stabilized carbon cast iron that's going to form. So let's look and see how that occurs. So we start with our ketone, there's are six carbon ring with its carbon eel bond. We know we're in an acidic environment in the presence of H 30 plus. So that's going to readily give away a proton. So one of our lone pairs on the oxygen is going to snag a proton there with the electrons from that O H bond going to form water, going over to the oxygen as a lone pair, that's going to generate a rather unstable form where our oxygen in that C O double bond now has a positive charge which doesn't like very much, but it's going to be resonance stabilized with a carbon cast iron. So let's look at those resonance structures as I mentioned, this form where we have the C O double bond or the positive charge on the oxygen after it's picked up, that proton doesn't really like that. So the electrons from this double bond can come on up to this oxygen as a lone pair, removing that positive charge and leaving the carbon. Now with a positive charge since it only has three bonds. And of course, those lone pair can pop back down and reform the double bond giving you those two resonance structures. The key form here is the second one where a carbon has a positive charge, our carbon cast iron because that's going to leave it ready for the nuclear filic attack by the animal group. So that's a resonance stabilized carbo can buy in this form here. And I'm just going to erase um these arrows here in this residence form. So we don't get confused with our reaction mechanism and look at the next step where the lone pair on our Amin are finally mean, the lone pair on the nitrogen comes over to form that bond with the carbon in the carbon cast iron. So we have the nuclear attack on the carbo cast iron. So now we'll have our alcohol group here and we now have formed our first C N bond. So we've now completed the first part of our mechanism, the acid catalyzed nuclear filic edition of the, aiming to the carbon L C. And we now see that we have our molecule with its no longer got a C O double bond. We've got a C single bonded to a hydroxy group and R C now has a new single bond to the Amin and the nitrogen as a result of that edition has a positive charge. So our next step will be the deep rotation of the nitrogen by a water molecule. So the lone pair on the oxygen of that water molecule snags the proton that's on this nitrogen and the electrons from that NH bond go to form a lone pair on the nitrogen and get rid of its positive charge. So that's going for Mark Kabbalah mean intermediate, which will be the next part of this mechanism. So we've now completed the second part of our mechanism. And now the lone pair on our hydroxy group is going to react with that H 30 plus that we know we have, it's going to grab a proton from that the electrons from that O H bond, we'll go on to the oxygen to form water. And that is going to result in a positively charged oxygen making that group a very good leaving group to lead to our final condensation reaction. So as we see, we now have this positive charge on the oxygen, not very stable situation. So the electrons in the C O bond, there will go on to the oxygen as a lone pair, which results in a molecule of water being eliminated, which is our condensation reaction. So as we go to the next step, a molecule of water has been eliminated, and we're now going to end up with another resonance stabilized carbo cast iron. And we're going to get our C N double bond that we're looking for in our next step. So the elimination of the water molecule has left a positive charge on the carbons. It now only has three bonds. So it's now carbon cast iron, but that is stabilized by resonance, the lone pair on the nitrogen can come down and form a double bond with the carbon which leaves a positive charge in the nitrogen, that's our other residents form. And of course, you can go back if the double bond, the electrons in the double bond go back onto the nitrogen. So those are two residents forms. Um Whereas in the first case, we had a reaction with the carbon cast iron. Now we see the second form where we have the C N double bond, we're almost there to our final desired product. And we will get there with one last deep protein ation of the nitrogen in that second resonance structure. So I'm gonna go ahead and erase the arrows showing the electron movement in my residence structure. So we can focus on the reaction mechanism and look at our final de protestation step here. So we have the nitrogen gets depreciated by the water molecule by a water molecule. The loan putting the oxygen comes and gets that proton on the nitrogen and the electrons from that NH bond come over to the nitrogen to give it a lone pair and give us our final product. And now we see we have our final inning here with its C N double bond and the lone pair on the nitrogen. So there's our final product. We see kind of the three major steps of this process. Uh First, the acid catalyzed nuclear filic edition of the AMI to our carbon carbon. The second being the deep rotation of the nitrogen and then formation of the car bombing intermediate and then finally in step three, the dehydration reaction and deep rotation of the nitrogen to give us the final aiming see you in the next video.

Propose mechanisms for the three imine-forming reactions just shown.

Key Concepts

Imine Formation

Mechanism of Nucleophilic Addition

Acid-Base Catalysis

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