EAS:Synergistic and Competitive Groups - Video Tutorials & Practice Problems
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When two or more substituents are already on benzene, there are multiple new factors we must take into account. These include Steric Effects, Synergistic Groups, and Competitive Groups.
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EAS with Polysubstituted Benzene
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by now. We're really good at adding e s reactions. Toe unsubs, toot benzene by itself. And we're even pretty good at figuring out where to put the second group once you have the first one on there when you act with a mono substituted benzene. But what if you have two or more groups already on that benzene? Then what happens, guys? So now there's gonna be multiple new factors you have to take into account because now you have two or more groups. So this is called Polly Substituted Benzene. Okay, so when you have those two or more substitue INTs, there's multiple new factors you have to think about of where to add that third one or that fourth one of the fifth one, the first one hysteric effects. Now that you have two or more groups, you may have some sites on that benzene that are completely un reactive due to the fact that they're in between to stare, glee hindered groups. So, for example, the group in between two ter beetles like here that position or the position between two rings like a maybe a ring that on the chain and a female group ph stands for fennel, right? That wouldn't be very reactive. So thes air sites that just would not react. They would literally be the very last sight to react in an s reaction, because all the other sites are gonna be more favored than that one. Okay, so it's something have to think about when you're using s police of student, you have to avoid those spots that air between directly 100 groups. But guys, we also have directing effects because it turns out that the groups now they have more than one. You have to consider the directing effects of all of them, not just one of them. So the first type of effect that you could see is what's called synergistic groups Synergistic directing of groups. That's when multiple directing groups. Oh, not what I meant to do. That's when multiple directing groups all point to the same position. Okay, so here you notice that I'm adding a br to over fbr three. So this is gonna be an e a S Roma nation, right? However, we've got an issue. We've got two groups already on this benzene. So we have to analyze What are the directing effects of both of those. Well, nitro we know was a strong electron withdrawing group and Oh, HC, what is that? Is that an alcohol? No, Guys, you should know this from Orga one. That is a alga hide. Okay, we know that the C h o condensed formula stands for an alga hide. So it's actually an alga hide. So it's also a strong withdrawing, not strong to moderate withdrawing group is Well, so then we would expect these to both be meta director. So the nitro group, I'm just gonna draw its effects with a circle shape. So the nitro group is going to direct towards this meta position and this meta position. Okay, see how those air both meta to the carbon that it's on. Okay. And then the alga hide is going to direct towards this meta position and this meta position. Okay, because those are the ones that are meta to the carbon that it is on notice that two of these positions aren't gonna work in both situations because they both already have occupants. This one can't work. And this one can't work right? There's only one that can work. And that's this site right here because notice that both of them are directing meta to the very bottom carbon. Okay, when you have two groups that agree with each other to arm or we call this synergistic okay, we call that synergistic because they work in synergy. That's a word to me that they're working together. They're cooperating. Okay, so they're synergistic. And that means that we're going to get a high yield off whatever. We're trying to yield whatever trying to react, because everything is pointing in the same direction. So I would expect to get a very high yield of my bro. Mean, I'll draw the alga hideout so you guys can see what it looks like. Like that, right? C h o. And you're gonna wind up getting a high yield of the bro me in adding to the bottom because meditate, both of them. Okay, so let's synergy. Okay? And that's one of the more important effects that you could get when you have multiple directing groups. But guys, we also have another situation which would be competitive groups. How? But if you have multiple directing groups that actually disagree on where to substitute, then what do you get? Well, then you're going to get a mixture of products, you're gonna get lower yields mixed products because they're not agreeing with each other. They're not synergistic. Okay, so let's look at this example. We've got once again a brahma nation and notice that I've got my same two groups my nitro and my alga hide. But now they're in different positions. Let's see what happens. Well, what we see is that the nitro group I'm gonna make it Blue is gonna direct towards this position in this position, the two circles, it's gonna direct to the to bottom carbons those air meta but the alga high since it's not the bottom is going to direct towards this position and this position. Okay, so it was that they're disagreeing. The nitro actually wanted to go here. The alga hide wanted to go here. So what do we dio? Well, sorry, I'm trying to pick green. Okay, well, the short answer is you're going to get both, so let's go ahead and draw both. We're gonna wind up getting a group or a molecule where some of the bromine added meta to the nitro. And we're also gonna get that mixed with a bending product that has the bro mean meta to the alga hide. So we're gonna get a mixture, see how one of them wins and one loses or, you know, they they're basically competing with each other. One's gonna be happy. One is gonna be sad. Okay, in this case, my Alba, Highness, sad in this case, my nitro. Sad. So the answer is, Which one's gonna be the major products? And actually, you can tell which ones, major guys, the major product is going to be determined by the strongest activator. The strongest activator will determine the major product. Will you still get a mixture? Yes, but you can determine that one's gonna be greater. And one's gonna be smaller ones major and one minor. So my question to you is based on that definition. Which one do you think is gonna form in higher yield? Um, I'm gonna get more of the blue compound making the nitro happy or more of the green compound making the alga hide happy. You can talk to the screen. No one's judging you. You've probably been doing that this whole time anyway. Okay, So maybe maybe you're right. The answer is actually gonna be that The green is major guys, and the blue is minor. Okay, so you might be thinking. But, Johnny, you said the greatest activator. I thought that n 02 is stronger. Okay, remember, we learned that no two way you remember remembered it wrong. N 02 is the strongest deactivate er it's the weakest activator C h o or alga hide. It's not an activator, but it's a little bit more active than natural. Right? Nitro is at the very bottom of my badass activity chart. And then we learned that carbon ills are moderately deactivating. So that means that in terms of absolute activity, the carbon eel is actually higher. Then the nitro groups. So the carbon Neil is gonna win. And that would happen with every single group on that chart. If you go all the way up to Anna lean, all it has to do with is the relative activity of both groups. Okay, so it's not about which one is the strongest. It's about which one is the highest up on that chart. Which one is the most active compared to the other? So that's why my green is gonna win. That's why my alcohol is gonna win Because it's higher on my activity chart on my nitro is gonna lose because it's the very lowest one. Alright, guys. So I hope that made sense. You guys know about synergistic effects and competitive effects. Okay, so let's move on to the next video.