Phenol Acidity - Video Tutorials & Practice Problems
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1
concept
Donating vs Withdrawing Groups
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Hey, guys. In this set of videos, I want to talk about predicting acidity for females. So, guys, females are alcohol's right, but they're substantially more acidic than a regular alcohol due to the resonance effect. Okay, remember that you had these effects in your asset base chapter way back in the day that told you when something was gonna be a better asset. And it said that if you're able to stabilize the con, you get base. Then your acid will be more acidic. We'll think about funeral guys. Fennel after it gives up its proton because becomes Phan Oxide. Okay, fine oxide. You know, it's a negative charge. Negative charges aren't that happy, but fine oxide can resonate. Notice that it could make resonance structures inside the ring so we would be able to resonate the negative charge to here, here and here. What that means is that normally, the PKK oven alcohol is about same, same as water, pretty much. But the Peca of fennel is closer to 10. Okay, That's because of these residents stabilized. Um, this resident stabilized conflict base that you can make. Okay, it's more stable, and therefore the female is gonna be more willing to give up its proton. Okay, well, it turns out that we need to also understand how electron withdrawing groups and electron donating groups play into this situation as well. So, guys, in this example, when I have d that just means stands for E D group, right on electron donating group when I have w That's an electron withdrawing group. Okay, so in general, guys, we can say that if you're pushing electrons into the ring, do you think that's going to make it more acidic or less acidic? If you're a donating group, guys, that's gonna make it less acidic because of the fact that you're destabilizing the country of base. The country based already has a full negative charge. Do you think it wants more electrons being jammed up into that benzene? No. Whereas what do you What do you think about electron withdrawing groups? Absolutely. That's gonna make it more acidic. The Mawr electron withdrawing groups. We have the better because it's gonna pull more electron density out of the ring, and it's going to stabilize that conjugal face. Got it so really quick. Let's just do a quick example already. Go ahead and look at these four females and tell me which one you think is gonna be the most acidic female.
2
example
Identify the most acidic phenol
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So this questions asking us to identify the most acidic phenol, which is going to be a simple as identifying withdrawing groups and donating groups, remember that withdrawing groups are going to increase the acidity. So we're just looking for the strongest withdrawing group to be there. So let's go ahead, and I'm actually gonna start in reverse order. I'll start at D and then we'll work our way backwards. So look it. Let's just identify what are substitutes are. So I'm dealing with in our group. I'm dealing with a nitrogen. I'm dealing with an oxygen and a chlorine. Okay, quote. So it's identify each of these. So ch three. Is that a withdrawing group or a donating group? Well, since that's in our group, that's gonna be a donating group, right? So are it's not the strongest donating, but its weekly donating. Cool. Moving on. We have toe identify all of them nitrogen. It's got a lone pair. Okay, so we know that for sure. Pretty much any atom that has a lone pair, um, is going to be donating right? There's one exception of that, but almost all of them are donating, so it turns out that Normally, nitrogen would be strong donating group. But since it has this Carbonell next to it, it's just a moderate donating group. Cool, moderate. Donating. Um, that's gonna That's getting worse. Now, this next one is O with a lone pair. Uh, this is gonna be a strong donating group. So so far donating group on DWhite. I mean, by donating guys again, is electron donating group? So these air all in the E d g category are donating groups. Good for acidity? No chlorine. Chlorine is a halogen. Remember? Halogen kind of the black sheep of the family different than the rest Halogen is going to be, ah, withdrawing group. Okay, it's It's weekly. Withdrawing weekly, withdrawing our weekly e w g. So which one's gonna win? Well, I know that for sure. I've got three donating groups, which just sucks, because that's gonna make it less stable. But I do have one group that's gonna pull a little bit of electrons out and stabilize a little bit more. So this is gonna be an easy choice. My most acidic fennel is definitely a all right cool guys. So let's flip to the next page.
3
concept
O,P-positions vs. Meta-Positions
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so, guys, it turns out that not all positions are created equal, and it turns out that some positions are gonna have more effect on acidity than others. In fact, the meta position is gonna have a much lesser effect on acidity than the Ortho and pair of positions. Okay, meaning that whatever type of group is on there, it just means it just matters less. If it's on the meta and it matters more if it's on a north or pere, why is that? Think about the resonance structures that occur when you make a fin oxide. Remember that I told you guys that where would that negative charge resonate you? It would resonate to the top, to the side and to the side notice. What are those positions called respective to the O. Those are the Ortho pair of positions, right? So that means the negative charge will rest directly on Ortho pair positions and it will never rest on a meta position. Okay, So with that logic, what that means is that we know that a donator is gonna make it less acidic because it's going to destabilize the negative. And we know that it withdrawing group is going to make it more acidic. Okay, but if those same exact groups are in the meta position So these air meta and these are Ortho, right? I'm looking at Orthodox vs Meta. If I have a donating group in the Met a position, it is gonna be a little less acidic, but only slightly less acidic than normal. Why? Because this donating effect doesn't really matter that much. Because it's on the meta position. The negative charge never goes there. Same thing goes with a withdrawing group. Withdrawing group. You think this is great? It's gonna make it really acidic. But it's on Lee slightly more acidic if you rest on the meta position. Why? Because once again, the meta position doesn't really matter, right? Because the negative charge never actually sits on it. Okay, so in terms of acidity, that brings us to the following acronym. Okay, So if you're looking for an acidic fennel, what you're gonna be looking for is ah, what? Okay. And what a whop stands for is a withdrawing group in the Ortho and pair of positions. Okay, so you don't care about the metal positions? The metal positions aren't helpful for us. We're looking mostly at those having withdrawing groups in the Ortho and pair of positions. Okay, so that being said, why don't we take Ah stabat this question and tell me which one you think is gonna be the most acidic female?
4
example
Identify the most acidic phenol
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Alright guys. So notice that my groups are identical for all four finals. The only difference is the positions that they're in. Okay, So what I have for the first one is that I haven't Ortho a meta Anna pere. Okay, these air, all withdrawing groups. Very strong withdrawing groups. Okay, What I have for the second one is an or thel a meta and a meta would have for the third one is an Ortho a pere on a meta And then finally would have for the fourth one is an Ortho pere and Ortho surgeons gonna win. Which one's gonna have the most stabilizing effects on that thin oxide? And guys, it's obviously gonna be D because D is the whop de has withdrawing groups on the Ortho in pere. Now, does that mean the other ones aren't acidic? No, they're very acidic. They're doing great, But this one's a little bit better because all of the groups happen to be in those Ortho one pair of positions, so it's gonna be able to stabilize the negative charge in every position that it goes. Got it with the withdrawing group. Makes sense. Cool, guys, Let's turn the page
5
example
Identify the most acidic phenol
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Alright, guys. So which one was the most acidic female in this case? Well, actually, guys, I'm just gonna tell you right now. The answer was a Did you pick a Yikes? I'm sensing that a lot of you did not pick a but that's because maybe you forgot about withdrawing and donating groups. What kind of group is N M? Me too. Well, this is going to be in a mean derivative and an Allene derivative because you've got ah, lone pair right there. That means that this is a strong donating group, right? Electron donating group. So what did we learn about electron donating groups? Do they make a molecule or final? More acidic or less acidic? They make it less acidic. Okay, so we found out that, you know, if we're going to have a withdrawing group, then we want it to be in the Ortho one pair of position. Okay, But if all you're given is donating groups, then you wanna minimize the effect that they have, because donated groups actually destabilize. You're, um, your anti on. So then you want it to be in the meta position because the meta position is gonna have the smallest effect. So when you don't have any withdrawing groups, then you go to donating groups and you look for them in the meta position. Okay, so in this case, what I have is to donating groups that one's immediately gonna lose because they don't want to of them. They're already bad as they as bad as they are. I don't want to things that are destabilizing my funeral. So that's terrible. And then I have Ortho. Oh, um, then I have, um, donating group. That's Ortho versus Dining group That's meta on the dining group That's meta is gonna win because the Dorian Group that's Ortho is gonna be significantly destabilized when my negative charge goes there. But my donating group, that's meta will be fine because the negative charge never actually hits that carbon. So it's not gonna be as destabilized, and it's gonna continue to remain acidic. So So we have to think kind of backwards here. Since we weren't given any withdrawing groups, you have to go with the donated group that has the lowest effect on the final. All right, so the answer's a So guys, here's another one. It's gonna be tricky. Try your hardest, and then I'll tell you the answer
6
example
Identify the most acidic phenol
Video duration:
52s
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Alright. So to find the most acidic fennel again we're looking for what? Ops? Looking for withdrawing in the Ortho Pere. Do I have withdrawing groups or donating groups? So, guys, iodine is a withdrawing group. Okay, so thankfully, that means that we're This is gonna be more simple. We're just gonna look for the one that has the most withdrawing groups in Ortho. One pair of positions. So this one is? Oh, this one is Mm. This one is PM, and this one is M O. So the best one is gonna be a once again because A has all of my withdrawing groups in the Ortho positions which stabilizes the radical. I mean, not radical, the anti an awesome guys. So I hope that made sense. Let's move on to the next topic.
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Problem
Problem
Rank the following phenols in order of increasing acidity.
