The general addition mechanism looks pretty straightforward, but what if the π-bond is asymmetrical? How can we tell which side the –X will add to?
1
concept
How to add to asymmetrical double bonds.
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3m
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So in the previous video, I gave you guys two examples of al canes that were perfectly symmetrical. That would attack electric files. But it turns out that it's usually not that easy. Most of the time are dull bonds actually gonna be asymmetrical, meaning that they're gonna have different things on different sides. In that case, how do we decide where the Carvel Catalan goes and where the H goes or or wherever the electrical goes? Okay. And for this, we're gonna have to use the prevailing rule of this whole section. And that's called Markov Niqabs rule. So let's go ahead and check it out. So, Mark Kalashnikovs rule is basically going to be the rule that we use to figure out addition for asymmetric double bonds, which, like I said, is actually the majority of the double bonds that we're going to deal with. Okay, Whenever you do have a symmetric double bonds, you're going to get the possibility of forming two different products because now you can add toe one side, or you could add to the other. Okay, Well, what Mark Omnicom's rule states is that it's going to predict that the Carvel cat ion is always gonna form on the most stable carbon of the two. Okay, now, this is actually the definition of of more carbon cultural. It states that the intermediate is always going to form in the most stable location. You might have heard your professors say it that there's other ways to describe it. For example, some professors say that Mark common cause rule is that the H goes where the other H is our I don't know what professors keep saying that because that's not the real definition of where carbon cars roll. Yes, that is a shortcut. But it's not always true, okay? And I would rather you just memorize the true definition, which is that the Carbon County is just gonna go in the most stable location possible. All right, so let's go ahead and check out this asymmetric double bond and see what our options are. Once again, I'm gonna take the electrons from my dull bond. I'm gonna attack the h. I'm gonna kick out the X, okay? There's gonna leave me with two distinct possibilities. I have the possibility, First of all, that the H forms towards the top is that HBO's on the top. That means my car will carry and is at the bottom. Okay, But there's also the possibility, since this is a symmetrical noticed that my Delavan has completely different things at the top in the bottom that I had the age of the bottom and my car broke it. And at the top, that's another possibility of this edition reaction. So which of these two is gonna be the more stable Carl Catalan? And if you guys remember, Carvel, Canadians are stabilized by our groups. Okay, so the more are groups that I compile around that car balcony, and the better so one of the is actually gonna be much, much more stable, and that's gonna be the blue one. Okay, so it turns out the red one is so unstable that it would never even formed. Okay. And that's more common cause rule for you, where Kalashnikovs rule of saying that you're only going to get the blue one or the one that has the most stable carbon kata and noted that notice that this was tertiary while this one was primary. Okay, there's a huge difference there. Tertiary Carvel candidates are much more stable. Then primary carbo candidates. So now that I know which car battalion is gonna form now, I just need to draw my final product. The X minus is now going to attack there. What that means is that my final product is gonna just be a molecule that looks like this. Okay, Now, notice that I didn't draw the age because I don't have to. Age is air always implied unless they're attached a hetero atoms. So what that means is that this is my final product. I'm not going to get a mixture of products. I'm only going to get 100% of the market knockoff product. Does that make sense? Cool.
Markovnikov’s Rule predicts that the carbocation will ALWAYS form on the more stable carbon, or the carbon that can eventually become more stable.
Note: Some professors teach that the “H will go to the side with the most H’s”. While this is usually true, I believe this misses the greater concept behind Markovnikov’s Rule, so I stay away from this explanation.
2
example
Provide the mechanism
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1m
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So let's go ahead and do an example. And for this one, once again, I want you guys to pause the video, try to draw the entire mechanism on your own and then predict the correct product. So go ahead and pause the video now. All right. I really hope you guys give this a try, because this is a very important mechanism that you need to know. So my total bond would grab the age. I would kick out the X. What I would wind up getting is Well, where is the h gonna attach to? Is it going to touch the secondary spot, which is right here, or the tertiary spot, which is right there, I hope you said secondary. When I ask it like that, it's confusing. But the H would attached to here so that my car will kata and conform their okay. The biggest difference is that my I want my car broke a tie in tertiary as much as possible. So I wanted to go right there. Okay. Now that I have it there, my ex negative is free to attack. And my final product would just look like this. It would be a metal group and an ex both coming off of that tertiary position. All right, so I hope that made sense to you guys. This isn't really hard. It's just something that you need. Thio always apply market because rule is very prevalent in this whole section. So it's very important that you understand what it is and has to do with the car. Volcanic. All right, so if you have any questions, let me know. But if not, let's move on to the next topic.