Ranking Acidity - Video Tutorials & Practice Problems
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Why is this section important? Because not all acid-base reactions are that easy.
When to Use Factors Affecting Acidity
1
concept
Why we need factors affecting acidity and when to use them.
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Alright, guys. So at this point, you're already pretty good at determining the equilibrium for an acid based reaction if you have the PK information. So I already taught you that you would compare the PKK of the acid and the conjugate acid. You would see which one stronger and weaker, and that will determine your equilibrium. But what if you don't have PK information? So what if you have an asset based equilibrium question and the two compounds that you just don't know the P. K s four or there's other situations to where PK information might not be that hopeful And that's when we're gonna use the factors affecting acidity. Okay, so for the next few pages, what I'm gonna do is I'm gonna introduce five factors that even without knowing PK a values, we can still tell which one's gonna be more acidic and less acidic based on these factors. So let's go ahead and get started. So, as I mentioned, there's five major factors and we're really gonna use these factors in two different situations. Okay, The first situation is that PK information is unavailable. Oops. Un available for molecules. So what that means is that Maybe you didn't memorize it. Or maybe your professor didn't give it to you. Or maybe you did memorize it, and you just forgot it. Hey, if you're at a test and you don't remember it, it's unavailable. All right, so then you might want to use factors affecting acidity. Ah, second instance would be if the PKK's of two molecules are two similar to make a determination of highest acidity. So imagine if you're comparing to carve oxalic acids. Well, they're both gonna have the PKK of around five. So how do I tell which one's more acidic and win friends less acidic? Well, with Piquet information, you wouldn't really be able to do that. So we're gonna need toe look even more in depth into these acids. Okay, So whenever we're analyzing these five different factors, what we're gonna do is, instead of looking at the acid, we're actually going to look at something else, and that's gonna be the stability of the conjugate base. Okay, how does this work? Okay, well, the reason we look at the stability of the conjugate base is because that's going to tell us how willing the molecule is to give away a proton. So the more stable the conjugate conjure gets, the more willing the acid is gonna be to donate a proton. How does that make sense? Well, remember, the conjugate base is what the acid becomes after it reacts. Okay, If the conjugate base is very, very stable, then it's going to say, Hey, I'm fine giving up a proton as an acid because if I give up a proton, I'm just gonna be this really nice, stable conjugate base. Awesome. All right. But what if the conjugate based sucks how? But if it's just like the worst conjugated life, it's not gonna want to exist very much. Okay? So instead, it's gonna say, Hey, I'd rather stay as the acid and have the proton on myself. So basically, the dissociation constant, the likelihood of me giving up a proton is gonna increase as my conjugate base becomes more and more stable. Does that make sense? And that's what these five effects have to do with. They have to fact they are going to either increase the stability or decrease the stability of the conjugate base. All right,
There are two situations in particular that making predicting equilibrium challenging:
You don’t know the pKas of the acids (so how can you tell equilibrium?)
The pKas for the acid and the conjugate acid are both the same (again, what do we do?)
No matter what, we know that the stronger acid will have the more stable conjugate base. Remember, reactivity and stability have that inverse relationship we talked about.
The Element Effect
This effect describes the way different atoms donate protons. For example C-H vs. N-H.
It consists of two trends:
Electronegativity (EN) – the stronger the EN, the more stable the conjugate base will be with extra electrons.
Size – The bigger (squishier) the atom, the less the conjugate base “feels” extra electrons.
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concept
Understanding the Element Effect.
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6m
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Let's go ahead and look at the first and easiest one. And that's the element effect. Okay, so the element effect determines how loosely or strongly a particular element bonds with hydrogen. Okay. And we can use these effects to compare different protein ated elements to each other. So, for example, a perfect example of using the element effect would be having like a nitrogen attached to an H and a sulfur attached to the age. Do we know the PK of the nitrogen? Actually? Yeah, I taught, I taught you guys that the PK of NH three should be around 38. Right. What about S. H. Two? Did he teach you? That one actually didn't teach you. So then in this case, if I were to ask you guys which one is the most the strongest acid, you would have really no clue on how to tell me, because I never gave you the P. K. Of S. H. Two. So that's why we have to use these factors. Okay, so it turns out that the element element effect is going to consist of two trends, and the first one is electro negativity. Okay, so electro negativity just says that the stronger the electro negativity, the more willing the molecule will be to accept a lone pair as the conjugate. Okay, so here's the electro negativity trend. I'm just gonna say E. N. And what that basically says, let's just put it this way we have, let's say H. F. Okay, which is an H attached to the most electro negative atom. And then let me say that we have also C. H. With also an H. Three over here. Okay, so I'm just giving you and that's a little bit off the screen. But can you see that? That's just an H. On the side. Cool. Great there. Okay, so anyway, we've got HF and we've got CH four. Alright. And what I'm wondering is after each of these molecules gives up a proton, what is it gonna look like? Well after this, this gives up one proton. H. Plus, what it's gonna look like? Is this F minus? Does that make sense? Because you always exchange a proton for a lone pair? So it's gonna turn into F minus. This is the conjugate base. Okay, now let's look at the conjugate base for the carbon, The carbon when it gives up its proton. By the way, I'm drawing this arrow wrong. This is not a mechanism. Arrow. This is just like me showing what happens next. Okay, what that would look like is like this CH three negative. Okay, so these are my two conjugate bases. My question to you is which of these conjugate bases is the most stable? Which of these is the happiest having that lone pair or that negative charge on it. And obviously the answer must be that it would be the flooring, why? Because flooring is the most electro negative. So it's the one that's happiest having electrons on it. Whereas carbon is really not electro negative. So carbon sucks. This carbon is really, really bad. That's like a terrible happy face. Sad face. This carbon is really, really bad. This flooring is like kind of happy. It's okay because it's a very electro negative. So it doesn't mind having a lone pair. So does that first trend make sense so far? Now, let's look at our, at our periodic table here, We were comparing nitrogen and sulfur. Okay, so nitrogen at the periodic table is here, sulfur is here. So just with the electro negativity trend, which of these do you think is going to be the better acid? The nature of gender? The sulfur. Hopefully you said the sulfur because even though you don't know the PK of the sulfur, you know that the sulfur is more electro negative. Is that cool so far? So it's gonna be happier with the negative charge. But now it turns out that there's another effect that we need to know another trend. That's to do with the element effect. And that one is the size trend. Okay. And what the size trend says is that the bigger or the squishier that the atom is. Okay, I'll explain what squishy means in a second. The more willing it's gonna be to accept a lone pair. So I'm gonna give you guys now two more examples still using flooring. So imagine that I have um f negative and f negative looks like this. Okay, the negative charge has to do with like a lone pair that accepted over here. Okay. Now, what I just drew was the electron cloud. Like there's a lot of electrons circulating and I just drew like the electron cloud. Now let's compare that to iodine. iodine is at the bottom down here. iodine is a much bigger atom. Okay. I mean the atomic number is like I think that's 53. So it's really, really big. It has 53 electrons. So instead iodine is gonna look like a sun compared to flooring. It's gonna look massive. Okay, so iodine is super super massive. Flooring is little and iodine also has a negative charge. Okay. And it also has a lone pair. Okay, so which of these do you think is gonna realize which of these do you think is going to be most affected by the lone pair? Okay. The answer is that flooring is more electro negative than iodine? Okay, I agree with that. But also flooring is a lot smaller. So that means that it's going to feel the effect of that negative charge way more than the iodine will. The iodine is so big. It's like I don't care like I don't mind having an extra loan pair because I'm a massive. Okay. And that's what I mean by squishy it's like really like big and squishy. It has a ton of electrons everywhere. Whereas flooring is kind of small even though it's very electro negative, it's still is way smaller. So overall it's gonna experience the effects of that negative charge more than the iodine one. Alright, the iodine honestly doesn't care. It could give up an electron, it could gain an extra electron. It doesn't it doesn't matter. All right. So the answer is that with size you also become more acidic. The further down you go, the more acidic you are. So if I work to compare H F versus H I. Okay. And I went ahead and I gave up a proton in each of these, I would I would become as F negative and I would become I negative as my conjugate base spaces. And then which one would be the most stable conjugate base the eye negative. Why? Because the eye negative, like I drew is much much bigger. So it's going to be able to distribute those electrons in a much bigger space than the flooring. Well, so it's gonna be more stable. Okay, so that means that the stronger acid is gonna be a chai Okay, cool. So hopefully that makes sense to you guys in terms of the element effect. Now, just keep in mind that the element effect only has to do with atoms that are directly hydrogen that are directly attached to different atoms. Okay, so let's go ahead and do these examples down here. So for one, I'm gonna have you guys we already did some of these. So I was just kind of working ahead but showing you guys using the element effect. So for one, go ahead and take a break and try to solve this one and predict which one is going to be more acidic. All right.
NOTE: This effect can only be used when comparing the way different atoms are attached to hydrogen. If you are comparing O-H vs. another O-H, it won’t work!
Without using pKa values, which of the following pair is more acidic?
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example
Using factors affecting acidity to rank acids
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2m
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Alright guys, so, using the element effect for number one, it was pretty obvious that S. H. Two has to be the better acid over um NH three. And the reason is because not only is S. H. Two gonna be more electro negative. Okay, because it's more to the right, Okay. As we said, that according to periodic table, sulfur is more to the right, but it's also further down on the periodic table as well, which means that it's also bigger. It has a bigger size and it has more lecture negativity. Okay, So it turns out that sht was actually much more negative than NH two. And actually just you guys know the P. K. Of S. H. Two in case you were curious is around 10. Okay. Do you have to memorize that? No, but I'm just letting you know that 10 compared to 38 is a huge difference. So, we were actually able, even though we didn't know the peak a we were able to predict the PK of this just by just by using element effect. Isn't that cool? So we were able to predict that it was a lot smaller. So let's go ahead and start on the second question. Go ahead and try to solve
Without using pKa values, which of the following pair is more acidic?
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example
Using factors affecting acidity to rank acids
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59s
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Alright guys, so for this one, what we're looking at is the atoms that are directly attached to the age. So I would have a see here that I'm looking at. I don't have Oh here that I'm looking at because both of those are directly attached. And for these, both of them are in the same row. What that means is that carbon and oxygen have the same size? So the size effect isn't gonna matter at all. Okay, but what is gonna matter is electro negativity? Remember that electro negativity gets higher as we go to the right? So that means that my water is going to be have a higher I mean going to have a higher acidity than my CH four. And remember I said, you can't use P. K values, you can just use just try to use the element effect. But if you wanted to double check, you could think about the P. K values. Remember the PK of water is 16 and the PK of CH four would be around 50. Okay, so obviously water is going to be a much better acid. Alright, so let's move on to the next question
Without using pKa values, which of the following pair is more acidic?
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example
Using factors affecting acidity to rank acids
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1m
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Alright, so for this one, what we have to look at is what are the atoms that are directly attached to the ages? Okay. So in this case I have an oxygen but there's no H. Is attached to it. So I have to look at the carbons next to it and the carbons are what have the hydrogen on them. Okay, so I would have basically CH vs. NH Those are my two bonds that I'm looking at. So then I would look at where those are on the periodic table. They happen to be right next to each other. Okay, So the size effect once again isn't really gonna come into play. But the electro negativity effect is this one is less electro negative and this one is more electric native. So that means that the N. H. Is going to be the one that is the most is the strongest asset. Okay, So that means that it would be this one and if you use P. K. Values, which again I told you not to use, but if you just wanted to confirm it, you would see that the PK of this one is around 50. Since just sp three CH and the PK of this one is about 38. Alright, so now we're gonna move on to our last one
Without using pKa values, which of the following pair is more acidic?
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example
Using factors affecting acidity to rank acids
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Alright so for this one I'm gonna take myself out of the screen so I don't cover it up. And this one we already solved. But I just wanted to point out that the reason is because the H. I. Has the higher size so it's gonna be more acidic than H. F. Even though F. Is more electro negative. All right. Um Now some of you guys might be wondering I'll come back for this part. So some of you guys might be wondering johnny, why do I have to look at the conjugate base? Can't I just look at the acid? Because so far I haven't been drawing any conjugate bases. I've just been looking at acids. Yes, you can. As long as you understand what's going on, as long as you understand the res reason why it's more stable because of the conjugate base. I'm not gonna ask you to draw the conjugate base every time. As long as you understand the reason why it's more stable is because that conjugate base is more stable. Does that make sense? That's why it's a better acid. Okay so hopefully that makes sense. Let's go on to our next factor that affects acidity.
The Inductive Effect
This effect describes the way that electronegative atoms that are NOT CONNECTED to the acidic proton make the conjugate base more stable.
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Understanding the Inductive Effect.
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Let's talk about the second factor that affects acidity, and that is inductive effects. So inductive effects describe the stabilizing properties that electro negative. Wait that down. Electro negative atoms that are not connected directly to the acidic hydrogen have on the overall acidity. Now, notice what I did to this word not connected this phrase. I made it bold. I made it underlined, and I made it all caps. So do you think that's kind of important? Yeah, right. It's very important. I need you to realize that this is kind of different from element effects. Element effects had to do with the atoms that are directly attached to the H. Okay. Whereas inductive effects have to do with atoms that are not attached to the age, that means they're on other parts of the molecules. They could be two carbons away, but they're still gonna affect the acidity of the hydrogen. Okay, so that's the difference between element and inductive. Okay, On the way that works is that whenever a charge can be de localized over more than one atom, that's that that conjugate base or that charge is gonna be more stable. Okay, so remember what's going on here. Remember that all of these acids, they're always gonna give up alone pair. I mean, they're gonna I'm sorry. Give up a proton and they're gonna get a lone parent return, and they're gonna turn negative. And that's called the conjugate base. If I can spread out that negative charge over multiple atoms, that's gonna make my molecule more stable. All right, so the way that works is that, um, by the way, the localizing all that means is spreading out. Okay, so when I d localized a charge, that means instead of it just being in one place, I let it be in two or three places. I spread it out over an entire molecule.
Any EN force that helps to pull electrons away from the conjugate is called an inductive effect. If you can spread out that negative charge over multiple atoms, that base will be more stable.
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example
Using electron clouds to understand the inductive effect.
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3m
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So let's go ahead and look at this example Here, Um, here. I have to acids. Okay, so we're gonna go ahead and draw some electron clouds in order to figure this out. But first, I just want to ask you guys, if you didn't know about this trend, could you solve this question with PKS? Which, let's say, which one is the stronger acid? Could you solve it with PKS? Actually, no, you couldn't, because we said the PK of alcohol is roughly 16. So this one is 16. And this is also an alcohol at 16. So according to my peak A rules, I cannot tell the difference of which one's more acidic and which ones less acidic. All right, so this is one of those examples where my PKK's air to similar to tell the difference. So I'm gonna need to use a factor affecting acidity. Now, check this out. Both of these have the same exact element effect because in both cases, I have an oxygen attached directly to the H. So is the element effect gonna be different at all? No. Okay. They're the same. The election negativity is the same. And the size the same because they're both oxygen. Okay, but what is different about these is that one of these has three florins, really far away. And then one of these has two florins. Really close. So let's see how that's gonna affect it. This is the part that I was talking about. Election. Negative things that are in other parts of the molecule will affect the H. So what I want to do is okay. Giveaway in each give away an age. And what we're gonna get now is the conjugal basis. Let's look at the conjugal basis. The kanji basis look like this Basically a negative charge in the O here and a negative charge in the Oh, here. The only difference is that when I draw, like, if you if I want to draw, like an electron cloud of where those electrons are for the O on the left hand side, it would just look like this pretty much. All those electrons would reside just on that. Oh, meaning that these are localized. Okay, but then check this one out over here. This one has thes two very electra Negative Adams right next to it. So what that means is that instead of all the electrons being around the oh, some of them are going to get spread out over these florins. Okay, So what that means is that I'm gonna have less of a charge around my Oh, and I'm gonna have a little bit more of a charge in other parts of the molecule. In fact, if I were to draw this again, I'd probably make this part around the even a little bit smaller. It probably looked more like this, like, more spread out like that. Okay, now you're never going to be asked to draw this. This is just my example. I'm just trying to get you guys to see how one of the contract base is gonna look different. But if you had to guess which these congregate basis is more stable, which one would it be? It would be the one on top of me. It would be this one, because this one is d localized or spread out. Okay, So what that means is that if one of these acids, if both of these assets had the same opportunity to give a proton, the one that would say Oh, me first, me first would be the one on top of me. The one on the right. Why? Because that's gonna be the one that forms the more stable conjugal based right here. Whereas the other conjugal based that one like kind of sucks because it's all just in one place. Is that Does that make sense? Guys cool.
Factors that increase inductive effects:
Strength of EN forces:-F > -Cl > -Br > -I
Number of EN forces:The more the better
Closeness of EN forces:The closer the better
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concept
The 3 factors that determine the strength of inductive effects.
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So now what I want to talk about is what are the things that increase or decrease inductive effects? And there's actually three things that we want to look out for. Okay, so first of all, the strength of the Electra negative entities. Okay, so the reason I'm using the word entities I know that's like a weird word is because it's not always going to be an atom. Sometimes it could be like a part of the molecule. Sometimes it could be like many atoms together. Okay, But anyway, the strength that means that flooring is actually the best thing that you can use. Thio have a inductive effect because Florence is the most election negative, Adam. So that means if I were to rank, the halogen is in order. It would be flooring, then chlorine, then bro Ming and then iodine. Okay, Now check this out. This is actually runs completely opposite toe the element effect. Remember that in the element effect, the best halogen was iodine, right? Because with the iodine, remember, it was really big and squishy, and it could have a lot of electrons in it. But in this case, remember that the H is never directly attached to this halogen in inductive effects in inductive effects. All I care about is which one is the most Electra negative to take the most electrons away. Okay, so what that means is that actually, it's going to be the opposite. In this case, Florian is always gonna be the best thing that you could have. Okay, then the next thing is the number. The number just means the more the better. Okay, so if you have, like, let's say that you have three florins on one of them and to Florence on the other, the three florins would win. Okay? And then finally, the proximity And that means the closer the better. The reason that proximity is important is because if you're Electra, negative things are too far away. They're just not gonna have an effect on it all. And actually, that's what happened up in this conjugate base. This conjugate base had three flooring, so you might have thought that that was gonna actually be better. But it's so far away from my oxygen that is not gonna be able to have any effect on that electron cloud. Does that make sense? And the General rule is that if you are three carbons away or more so three carbons or more or three atoms or more, then you'll have no effect. Okay, So what that means is this is this would be 123 Anything after that is not really gonna have an effect on the oxygen, because just too far away, all right. And I just realized that I was writing that off the page, so I'm just gonna move that up a little bit so I could see that I said three atoms arm or would equal no effect in terms of distance. Okay, So what that means is I want the strongest things. Florian's mawr of them as many as possible. And the closer the better. And that's gonna be what makes my acid more acidic because it's going to stabilize the conjugal based more cool. Once again, a few guys might be asking me, but, Johnny, can't I just look at the acids instead of the conjugate? Yes, you can, but I need you to understand why it's more stable. And the reason has to do with these electron clouds. Okay,
Without using pKa values, which of the following pairs is more acidic?
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example
Using Inductive Effect to determine acidity
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1m
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So now what I'm gonna do is I'm gonna give you guys this problem. That is actually really easy. But I'm still going to give it to you guys just as a free response. Go ahead and try to solve, which would be the more acidic, the right or the left. So go ahead and pause the video and tell me so the answer is Obviously this one would be more acidic. Okay, Because this one actually meets all three criteria. It has some election negative things that are not attached. She has four florins, Okay? It has a lot of them for and they're all really close. They're all exactly on the alcohol. So this is an example of just a really easy question that you could get now. So you guys might also be asking this. But, Johnny, how about if my professor gives me one, but not the other? And if he switches them up? So, for example, what if on one of them one of the acids has a bro mean? But then the other one or one has to bro means. But then the other one has one flooring. How do I know which one is better. And my answer to that is that professors are never that mean. So what they're going to do is because the only way to figure that out would actually be to do math and to actually do, like, empirical calculations. So you're never gonna have to worry about like, Oh, this one has more. But this one is closer. Stuff like that, unless it's really obvious, like the one I gave you up there was obvious because it was way too far away. But if it was like you can't really tell the difference, you wouldn't get that kind of question. It's always gonna be like just these three things. Three things Paul together. So, for example, one of them, let's say this was an alcohol. One of them could be like having one chlorine and then the other alcohol could be like having like one flooring. And then you just have to pick the difference between those two. Okay, it wouldn't be like that. You're having to pick the difference between one flooring and to chlorine because that would be way too hard. Alright, so hopefully that makes sense to you guys. Let's go ahead and move on
Resonance Effects
If a conjugate base is able to make a resonance structure, it will be more stable.
Understanding resonance effects. Which of the following –OH groups would be more acidic and why?
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concept
Understanding Resonance Effects
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3m
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the next three factors aren't quite as complex. So I went ahead and group them into a category just called others. So let's go ahead and start with that third factor that effects acidity. And that would be resonance effects. Alright, so residents effects is actually just really easy. It's just whenever the donation of a proton, least of the formation of a possible resonant structure. Okay, that conjugate base will be more stable. And the reason that the countries will be more stable because it can resonate. Remember that residents structures enable for a charge to be in multiple places. That would make sense that it's d localizing the charge. All right. And that means that if the conjugate base is more stable than the molecule will be a better acid. Okay, so check this out for this example. I've given you 20 h bonds. Okay, so I have o h. And I have Ohh. All right, so we're not gonna use PKK's to figure this out. It says which of the following appears of essence would have the lower, but I'm not asking you to remember it. I mean, even though you you should remember it, But I just want to use the factors affecting acidity to figure this out. So for both of these do they have different element effects? Remember, the element effect is the atom that's directly attached to the H. So in this case, they both have the same element effect. So I'm just gonna write that here. Same element effect. Okay. And the reason is because they both have an oxygen attached to an H. That doesn't change. All right, so besides the election, obesity is exactly the same, but it turns out that one of these is a much better acid. In fact, one of these is called carve oxalic acid, and the other one is just a alcohol. So what is it about the car oxalic acid that makes it so much better as an acid? And it's the fact that let's look at the conjugate base is the conjugate base for my car. Looks like acid. Looks like this. Oh, negative. Okay, the conjugate base. So I'm just gonna put here. This is CB conjugate base. Alright. The conjugate base for my alcohol looks like this. All right, so which of these is gonna be the one that's more stable. Well, both of them have a negative charge on the Oh, but notice that this Oh, is stuck. This one, that negative charge isn't gonna be able to go anywhere. So it's completely localized. Whereas on the other one, um, this one is actually gonna be able to resonate using the two arrow rule that I taught you guys in resident structure. So then I would make upon and there, and I would break upon there, and I would actually get a new resident structure that looks like this and sorry, it's a little bit crowded. I would get a new resident structure that looks like that. So what that means is that I'm able to distribute this negative charge over those three atoms. Isn't that interesting? So what that means is that one of them is going to be way more stable than the other. And that is why car books look. Acid has a peek a of five, whereas alcohol as a PK of 16. That's a huge difference. Really. If it worked for the carbon deal, that would still have that carbolic acid or have a PK of 16. But the Carbonell changes its silken resonate So now the PK is basically like a trillion times better, or like in terms of its it's like a trillion times more acidic, almost a trillion. Alright, so it's literally a way better acid. So that's called the residents affect. Any time you can make resident structures, it comes into play.
Hybridization Effects
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concept
Understanding hybridization effects.
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2m
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Now let's look at the hybridization effect, the hybridization effect. The definition is this that the higher the s character in an acid. Remember that we talked about s character when we were talking about hybridization, remember? We were, like saying, like, 25% s character would come from sp three, where you have like and s and you have three piece. So then 25% of the entire thing is s And that would be the s character. Okay? And the reason is because the S orbital is the one that's closest to the nucleus. Remember, it's the smallest. So the more s character you have, the closer, the lone pairs, they're gonna be held to the nucleus. And it's gonna make the content based more stable because you're gonna hold those electrons tighter. So the positive and it's gonna be a little bit more stable. So if we were to think about the acidity trend, what it would look like and by the way, just go ahead and add a stick there if you don't have one already. So for the acidity trend, would it would be is that s p okay has would have 50% as character because it's basically, um one part s one part P s P two would have 33% s character, and then SP three would have 25% s character. Now let's look at the PKK's underneath. I want you guys to draw in the PK so you guys can remember what they are and you guys can see how this trend is affected. So what was the PKK of NSP hybrid? I ch It was 25. What was the PKF sp to remember? This is Al Qaida, Al Keen and all Cane s b two b 44. And then what was, um sp three who was 50? Okay, so you can see how, as my s character gets higher as my s character is increasing, my acidity is also increasing. Does that make sense? So as you're s character is getting bigger, the amount of the whole hybrid orbital is s the more acidic you get
The higher the %s-character of the conjugate base, the more stable it will be.
Recall, %s-character = (s-orbitals)/(total hybrid orbitals) x 100.
Aka, sp3 = ¼ = 25% s-character
Which of the following hydrocarbons is the most acidic?
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example
Which of the following hydrocarbons is the most acidic?
Video duration:
16s
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So this is just a way to explain that peak a trend Which of the following hydrocarbons would be the most acidic? And you guys already know that it would be this one because this one would have an h there. And that would be SP hybridized. So it have a PK of 25. Is that cool?
Steric Effects
This rule really only applies with alcohols for now.
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Understanding steric effects.
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2m
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All right. So we get to our last one, and this is called Starik Effects. Now, I still haven't even talked to you guys, but what's Terex? Our But that will be coming shortly. But basically what Starik effects say is that particularly with alcohol. So this is really just going to deal with alcohols, The more easily solve aided. The conjugate base is okay, the more stable it will be. All right, So what the heck does that mean? Okay, solve ated. Wow, that's a huge word. It just means how easily it will dissolve in a Nyquist solution or how easy it will be mixed in an aqueous solution. All right. And what that means is that we want our alcohols to not be very bulky in order to mix. If if they are bulky, they're not gonna have this easy of a time mixing into the solution. So the rule here that you just need to know is that the smaller the art group, the more acidic the alcohol. Oops, acidic. Okay, so the smaller the art group, the more acidic the alcohol going all the way down to water. Let me show you an example. So basically, um, if I have hoh and then c h 30 h and then see, and then, let's say, just keep adding, I keep putting more and more groups. Let's say I had, like, something like that. Okay? I have these three different thes air. Not all alcohol's. These two are alcohols, and then one on top of is water. Okay, so just so you know, this first alcohol, um, that I have right here. Let's say this is gonna be, um this would be like, whatever. I'm just gonna say, this is just ch 30 h This first one have a PK of around 16. Okay, as I add our groups to it. So as I make our and our here, that Peca is going to start to go up because it's gonna be it's gonna be a little bit less acidic. So in this one, you have a PKF maybe around 17. Okay, it gets to the point where if you add enough are groups the PKK could go all the way up to about for for tribunal, which is one of the bulky ist alcohol's. Alright, then let's look at water, water instead of having an art group. It just has an H there. H is the smallest one of all. Remember I said smaller. The our group will h is really the smallest that it could get. Right? So that means that water, actually, as a Peca of 15.7, making it actually the best acid out of all of these. Why? Because the one of the smallest group next to the alcohol does that make sense. So basically the small, the bigger your group gets the worst of an acid, it gets okay, The smaller your group is the better and acid. Okay, so then the other trend is just the opposite of that. It would say the bigger that the our group is, the more basic the Alcock side. The Alcock side is just the name for the conjugate base. That would just be anything that has an O negative on it. Okay,
Particularly with alcohols, the more easily solvated the conjugate base is, the more stable it will be.
The smaller the R group, the more acidic the alcohol
The bigger the R group, the more basic the alkoxide
Which of the oxides is the most basic?
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Which of the oxides is the most basic?
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Alright, So yep, the one that would be the most basic would be this one right here on The reason is because that's called Turkey Talk Side and it's the bulky IST based out of all of these that has the most are groups sticking off of it. So would be the one that is the worst solve ated. So that means that it's gonna be the least stable conjugate base, which means it's the most basic. All right, so I know that that was a lot of like It means this, which means this. Just remember the rules. If you're confused, just memorize these rules and you'll be fine. All right, so now let's go ahead and do some practice.
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Would the following reactions go to the right or the left? Draw the products and label ALL species. Provide the full mechanism.
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Problem
Would the following reactions go to the right or the left? Draw the products and label ALL species. Provide the full mechanism.
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5m
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18
Problem
Problem
Would the following reactions go to the right or the left? Draw the products and label ALL species. Provide the full mechanism.
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6m
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19
Problem
Problem
Would the following reactions go to the right or the left? Draw the products and label ALL species. Provide the full mechanism.