- [Instructor] Hi there, welcome to the second half of what should've been today's lecture. I had to speed things along, I think I talked about IR a little too much, but I think it's really important to talk to you about chemical equivalency and predicting where proton NMR absorptions are expected, how many there are, and what they're worth. So, first I'd like to say that I hope the audio turns out good. I used to have a really nice microphone that was connected to some headphones, but unfortunately, there is a monster in our midst, and this poor little guy decided that he would chomp on my nice headphones. Anyways, this is what, this is the version that I wanted to go over in class today, you got the short version, here is the slightly longer version. So here are some simple examples of compounds that have only one type of proton, which means they're only going to have one signal in their NMR spectrum and we wanna have an idea of why there's only one signal, how many protons each signal is worth, which may be obvious and then what's its chemical environment because that's going to tell us where it shows up on the x-axis or in more technical terms, what is the compound's chemical shift in the proton NMR spectrum? So, the reason I left a lot of space is 'cause there's kind of a specific way to go over, determine whether each of these protons are actually the same or if they are different, now these are examples that may be obvious that those could be considered to have the same chemical environment and that they're equivalent, but I'm gonna start with simple examples, and I hope that you pick up on this quickly. So, what we do is we look at the Lewis structure of each atom, or each molecule. I'm gonna do this twice, so I'm gonna kinda, highlight this, I think I can do a little copy and paste okay, so the question is, if we were to take any two protons, let's say like this proton and that proton, the question is, are they the same? Do they have the same chemical environment? And the way that you can do that is to replace this proton with some other group, just say like an X, I don't even wanna give it an actual atom so let's say that group is an X, and we wanted to know if this proton is the same or not, so we would replace, on a separate drawing of that structure that molecule with an X, and we would figure out, are they the same compound or not? And in this case, they are the same. Notice that it's still, the X group is attached to a, so it's attached to a carbon, which has two hydrogens and that carbon is attached to another carbon which has three hydrogens, so again, the X group is attached to a carbon, which is attached to another carbon which has three hydrogens, so small molecule, but that's the way you do it, if you're not sure if any two hydrogens are the same or different, you replace one group at a time, one hydrogen at a time with, in this case, an X, just something else. And you could do that very same thing with this example of cyclohexane, I'm sorry, let me back up, that means that they are all equivalent, here, these are all equivalent, all equivalent protons and that's why you had only one signal. So now we can do the same thing, we have all these different protons in cyclohexane, so we have the two up there, any hydrogens that are attached to the same carbon are going to be equivalent, I hope you can see that they do have the same chemical environment, but you can use the same trick that we had down there before, to figure out that they are definitely the same or not. So let's say we're gonna draw our cyclohexane molecule, we'll draw it twice, and you're trying to figure out if the two hydrogens on that top carbon are the same or not, so if we were to draw one where it's like a X group here and then a hydrogen, versus another where this is an X group here, and that's a hydrogen, I hope you can see that these two are the same, which explains why those two protons are equivalent. I'm gonna do same idea, let's say we're not sure if the proton on the top and the proton on the bottom are the same or not, so let's say, you know, we're trying to figure out, is that guy the same as the one that's up on top? You would replace the one on the top with an X and the one on the bottom with an X, and once again you see that those two compounds are back the same. Great so now we move on to this methyl ether example, just write that, methyl ether so I don't keep saying it wrong. This is methyl ether, or dimethyl ether, same deal, and we'll draw its Lewis structure. All of the hydrogens in the whole molecule are equivalent to each other, we can use our, not really a trick, it's just the way to really do it to figure out if any two protons are the same or different so here's two drawings of the same molecule, so let's ask ourselves the question, are these two the same? They're connected to the same carbon so the answer should be yes, but I wanna teach you this technique, 'cause it's going to apply to more complicated examples. So let's replace that hydrogen and that hydrogen with X groups, here and here, and you see that those two protons are the same because those two, if that were an X group, that would be the same molecule. You could go ahead and do same thing, if you were trying to figure out if that hydrogen and that hydrogen are the same or different, so we're gonna replace that hydrogen with an X and that hydrogen with an X. Okay, so let's put an X group here, and an X group there. Those two are once again, the same molecule, if you rotate one, it looks like the other. And that's what helps us determine that all of the hydrogens in methyl ether are all equivalent, they're all the same chemical environment, so there's one signal in an NMR spectrum. So then we will go down to the next question, how many protons is each signal worth? And that's just asking the same question, because there's only one signal, how many hydrogens are in the compound? Here we have six hydrogens in ethane, we have 12 hydrogens in cyclohexane, and we have six hydrogens in methyl ether, so 12 hydrogens, (mutters). So one signal could be worth a lot of different hydrogens, you need some other information to figure out that, just from an NMR spectrum. But, cool thing that you can get is its chemical environment, we did this in class, but I think this is important, so just gonna help us understand where we actually can expect them on the x axis. For the example of ethane up above, you have a hydrogen attached to a carbon, which is attached to another carbon, and that functional group is actually not a functional group really, it's just an alkane, nice and boring alkane. The next one would be the same actually, any hydrogen on cyclohexane is just bound to a carbon which is bound to another carbon and there's nothing interesting going on, it's just an alkane. The last example is an ether, it's dimethyl ether, and for each of those, we have a hydrogen attached to a carbon, and that carbon is attached to an oxygen, so again, that's an ether, so this is the kind of formula that I'm using because that's gonna be what we see in our table of values to figure out where it actually lies on the NMR spectrum, so I'm gonna take you there so we all know where to find these things, so I'm just gonna, switch apps here and go to the class website, this is at the very bottom of the CHEM8M website, and here are the NMR intro tables, so there's a couple little figures in the front that could go over what resonance frequency actually is, how it kind of like flips the spin of the atom. We talked a little bit about that, and I had some pictures here, really just so you could see some of the inner workings of the instrument. Mainly what we care about is what you see on the printer display. What actually the peaks are. So that's there if you're interested, there's a couple little reminders here, of what downfield and upfield are with regards to shielding and deshielding. Here you see some examples I'm actually gonna go over a little bit later in this video, just some examples of what NMR spectra look like, what I really wanted to get to here is page three, but I wanted to take you there, where you can see where different protons show up on the x-axis, depending on what functional groups they're bound to. And we have two different pictures, I like this one here because it gives you a relative idea of where the functional groups show up with kind like little snapshot pictures of the simple version of the functional group. But down here, you have that same exact information, but it's just given in table format, so we could actually look up, for example, where ethane or cyclohexane would show up, we already noted that they were alkanes, where you have a hydrogen bound to a carbon, which is then bound to another carbon, and we can see that little area between .8 and 1.9 is where we would expect both of those compounds to show up, so I'm gonna switch back. Both of these, once again, would show up between .8 and 1.9 parts per million, and within this video, I'm going to also explain those units as well. So a bit different for the ether, let's go back, we're looking for a hydrogen connected to a carbon that's connected to an oxygen, so we're looking for an ether functional group. I can't actually draw on this 'cause it's a webpage, it's not my annotating thing, but right there, like in the middle-ish, bottom, we see a section on alcohols, esters, and ethers, where there's a hydrogen that's in bold bound to carbon bound to an oxygen. And that's gonna show up between 3.2 and 5.3. 'Kay, so that's where we'd expect diethyl ether to show up, dimethyl ether and I have that on the second page, and you guys can see all that, what's happened before, page three in the lecture webcast. So now we're kinda caught up, this is what I did, sorry, this is the section of the notes that I went over in lecture, but as you can see, this is a really different, at least for the top, it's kind of a different approach in terms of replacing one hydrogen with the X or not. But I wanna apply that to a more complicated example and that's this guy down here, which has a lot of interesting functional groups on it, and we wanna figure out how many proton NMR absorptions are expected below. Now the reason I have multiple drawings of the same molecule should be a little bit more clear now, because I wanna give you the opportunity to actually draw these structures with different groups on them to see if certain protons are equivalent or not. So the first thing that we did, we kinda categorize 'em, we looked for CH three groups, so we had two different CH three groups, and we just kinda made that known to start off, but we could get a little bit more into it since I have this time, we have two CH three groups, and in order to actually use that thing (laughs) above or the technique, we would replace one of the groups, so let's say that both of those just have two hydrogens now, we replace one of them, one of the hydrogens with an X group sorry I did that wrong, so this is supposed to, stay, this one's supposed to stay a CH three, and then let's say this one over here, is now a CH two X, so I hope that you can look at these two compounds and see that they are for sure different compounds, think it's important to see the examples where they're different 'cause up above they were all the same. So up above, all the times that I did that was the same. But now those are very different compounds, which further confirms that those two CH three groups are non-equivalent, they are different, easier way of going about that might just be to say that hey, this methyl group right there, or maybe let's do it over here, this methyl group right here has an oxygen near it, this methyl group right there does not, so those are different. Okay, great, so I'm just gonna call those, on this cleaner version over here, I'm gonna call that signal one, and signal two, only because those are the first two that we identified, this has nothing to do with where they actually lie on the spectrum, I just wanna keep track of how many there are, okay, so let's restart. Okay, so just clean those up, now let's go to the CH twos, the methylenes. We have only one, so see how many CH twos, there's actually one CH two group, this guy right here has two hydrogens, since those are attached to the same carbon, they should be equivalent, but the way that we figure that out is by replacing one hydrogen at a time with a different group. So let's say, on this first example, we're gonna replace the hydrogen with X group, and then the second one, we'll replace the other hydrogen with an X group. So those two are the same which means that those two hydrogens are equivalent, and that here, this accounts for just a third signal as opposed to being a third and a fourth signal for the two hydrogens. Actually, what I should be doing here is making a little note that blue signals I call it is a two hydrogen signal, let me get rid of the apostrophe S, it's a two hydrogen signal, each of the ones that were in red, those were three hydrogen signals, okay, so we have three signals, and then I'm kind of keeping track of the ratio of peak areas. That maybe should be something I do more towards the bottom, but it will be already answered for us, so that's what I'm doing here, this is gonna give us the ratio of peak areas once we integrate them, but we can kinda do this all at the same time. Alright so the fun really begins when we look for all the different CH groups, so now I'm gonna add in one hydrogen at a time, so the rest of the carbons in the molecule have only one hydrogen attached, with the exception, before I get into it too much, of these two, these two carbons have no hydrogens, so we would expect no signal for them because there are no hydrogens. That's kind of all there is to it. Anywhos, so we're tryin' to figure out if these two hydrogens are the same or different. We can do the same thing for all of these, but I'm gonna start one at a time. I'm gonna first compare if those two are the same or not, and we do that by replacing one hydrogen with an X group, let's say one of 'em, yeah it'll be an X group here. X group here, in order for this to actually make sense, I need to remove these and I'm trying to figure out if those two are the same compound. Because you can do some rotation. And there's symmetry in the molecule so even better, we see that there is symmetry here, boop boop boop boop boop boop boop boop boop, through the molecule, so we find the same thing happening on either side, because of the substitution of that ring, so these two are drawn, if they're Xs, are the same compound which means that those two CH groups that are right next to that ether group are actually the same hydrogens or rather, they would account for one signal. So this would be our fourth signal, and this account for two hydrogens because we had two equivalent protons. So that's important, I wanna make sure that's clear that the two hydrogens that are next to that methoxy group, are equivalent. This guy and this guy, these are equivalent protons. Now we move onto the next set of CH twos, we have these two hydrogens here and here, and these two hydrogens have the same relationship to the other groups on the ring, and once again, we have this plane of symmetry, so they're both right next door to that alkyne substituent, and then two carbons away from the methoxy substituent so those are are actually equivalent protons, and once again, the way that we work that out, is we replace, one at a time, with an X group, I'm gonna clean up the rest of this stuff here, one second. Here we go, replacing, one at a time, with X and X, and we see that those two are the same compound, and then we have some rotation around the molecule here where you can see that like you can flip the molecule and you can see that these two, once again, are the same compound. So those two hydrogens that I had labeled in blue, those are equivalent signals, or equivalent protons. There it is, hooray, they're equivalent protons. Now we wanna make sure the relationship between those protons and the ones we have labeled in green. And it turns out, these sets of protons, these two, are non-equivalent, they are different. Now that may be something that's clear just by looking at the structure itself, but the reason that I'm putting this video together is so you can actually use that technique to figure out, unequivocally, whether or not they are the same, so here we're gonna clean this up, one second. So I just simplify, letting me replace, we'll call it the blue line, we'll replace with an X, whereas over here, we'll replace the green line with an X. And I hope that you can see that these are different compounds, these are different compounds, because here, we have the X group, it's two carbons away from that ether group, whereas here, the X group is now one carbon away. Because those two are different, we then call this set of CHs a new non-equivalent signal, it accounts for two hydrogens because we do have equivalent hydrogens, right, so these guys are equivalent to each other, but these two hydrogens, we know, these two sets of hydrogens are non-equivalent, meaning they do not have the same chemical environment, so they'll be showing their own unique signals in the NMR spectrum. So that takes care of two CH signals, but there are still two more carbons, two more sets of hydrogens we have yet to explore, and those are the vinylic protons so I'll write that down, those are vinylic protons, they are hydrogens connected to carbons that are involved in an alkene. So the question is, are they the same? And so what we do is we replace one hydrogen at a time, mirror and mirror, so in different examples, we'll place an X here, and an X here, we ask ourselves, are they different compounds or the same, I hope we all agree that these are, indeed, different compounds, we have the X group here, right next to the aryne group, whereas this one is two carbons away. So we do have two additional CH two signals, so we'll call this signal six. Signal six accounts for only one hydrogen, and then finally we have signal seven, so there's seven signals total, that's actually the answer to this main question that there are seven signals and signal seven here accounts for one hydrogen. So that's a lot of different things that we have there, seven signals, each signal is worth a certain number of hydrogens, and so that's what we mean by the ratio of peak areas. So how many hydrogens is each signal worth? What's going to be the relative ratio of each of the signals on the proton NMR spectrum. And it goes like this, three, to two, to two, those are the aromatic protons, we have one to one for these vinylic protons, we have the CH two group, so two hydrogens, and then that last methyl group, so you're gonna have seven signals and when we integrate those peaks, or rather when the instrument integrates the peaks for you, that's the ratio that you'll get, and because you have one hydrogen signals, those actually equate to three hydrogens, two hydrogens, two hydrogens, one hydrogen, and so on. Great, so that's what I wanna say about that. Now, we fill in this last thing, so this is the other way to get to seven hydrogens, or seven types of hydrogens. We said that there were four CHs, and that was the way that we did this in lecture that we got a total of seven signals. Now it's time to approximate the chemical shift for each type of proton, and which means we need to figure out the chemical environment for each signal. And we're gonna do that one at a time, so we have this set of protons right here, those are hydrogens connected to a carbon, connected to an oxygen, and that functional group is an ether. We don't go so far as to say that that oxygen is then connected to an aryne group, 'cause then we start to get too far away from the hydrogens, notice we've gone like two bonds away, these proximity effects are important, we'll see the limitations of that. So we're looking for the ether, we actually, I'm just gonna save some time, we already had the range for the ether there in the top right it is 3.2 to 5.3, so that's about where you'd expect this to show up, 3.2 to 5.3 on the x-axis, and I'll explain parts per million on the next page, I know you can't wait. Next we have all of these hydrogens, all of those red hydrogens there in the aromatic range to be a little more specific, these guys are hydrogens that are connected to carbons that are in the aromatic ring, or are an aromatic ring. So I'm gonna switch over to the table, remember, these are online, and we see that there are two, actually, two different places in the table that we find aromatic compounds, you'll find one in the middle, notice that it has, the one in the middle has a little b next to it, has Ar connects, so the aromatic ring connected to a carbon connected to a hydrogen. But our hydrogen is directly connected to the aromatic ring, so we wanna use the one on the bottom, third from the bottom, aromatic compounds, Ar-H, and that range is 6.5 to nine. So that's where we expect to find these protons. We then have, this hydrogen here, oh sorry let me jump back, so there are two distinct signals, these are different, and we'll talk about how, the other affects like how close the other groups are to that methoxy group, there are still two, we have two aromatic signals that are both in the 6.5 to nine range, so they just are in the same range, big range. Okay, so now we're at, the one that I drew in blue, this vinylic proton, vinyl, it actually can fit into a couple different categories, so this is where you'll be looking to see if it's like, you know, there's groups two or maybe even three carbons away, so we wanna categorize this hydrogen as connected to a carbon, which is involved in an alkene, right so that's this carbon, connected to that carbon, but, the carbon here that is directly connected to the hydrogen is actually connected to an aryne group, or rather an aryl group, an aryne, so it fits into two different categories, 'cause it's next to an aromatic group, and an alkene, so it's going to fit two categories which just means it's gonna be even more deshielded. I'm gonna erase this word vinyl, we can fit it into two categories but we're gonna choose the higher one being representative, so let's go back to the two categories, we're looking for an aromatic group, noticing that now, it's the (laughs) it's the hydrogen attached to a carbon connected to an aromatic group, and then the second category is a hydrogen connected to the carbon of an alkene. Alright so the first group we saw earlier in the middle, the aromatic compounds with the little b, is when the hydrogen's connected to a carbon connected to an aryl group, and that ranges between 2.2 and three. Translate that, so that range would be 2.2 to three. Let's look at the other group, or the other categorization. Where the hydrogen's connected to a carbon of an alkene and that is, one, two, three, four, five, six from the bottom, where the hydrogen's directly connected to that alkene, and then we have, that ranges 4.5 to 8.5, pretty big difference. 4.5 to 8.5, okay, alright, so this is the higher range, this is gonna have a bigger effect, these effects are however, additive, because we have this deshielding effect as well, the proximity to the aryne group, it just means that it's going to be, that proton in particular is likely to be on the higher end of that range. Alright, so then we move on to our next proton, which is also another vinyl proton. It's a hydrogen connected to a carbon. Hydrogen connected to a carbon that's involved in an alkene, it's too far away from the aryne group to have a huge effect, neh, as you learn more about protein NMR, you'll learn how, or rather, I'll teach you later on, how the effects actually do make a bigger difference, but for right now, we're just trying to do simple categorization based on the table that I've given you. So here, we're gonna see that we have 4.5, 8.5 is going to be the general range for that proton. Continuing on, we have these two protons here, and these two protons actually do fall in the alkene category, they are allylic, meaning they are hydrogens connected to carbons that are then involved in an alkene, so we can find those within our table. It's still in the alkene category, so if you go one, so there's TMS, alkanes, amines, alcohols and then alkenes with a little a, and that a goes for allylic, it's a hydrogen connected to a carbon connected to an alkene the range in 1.5 to 2.6. That's where you'd expect it to show up. So you can see a real big proximity affect of that hydrogen right next to that alkene is way more deshielded, electrons at being pulled away and it's kinda naked and less protected from the magnetic field, whereas in the allylic position, much less deshielding going on, so we see a much lower chemical shift. And then let's see if we can sneak in this one here, this is a CH three group, that's just an alkane, you just like zoom in, okay, so that alkane group is gonna show up somewhere between .8 and 1.9. And that's where they all show up, that's how you use the table that once again, is on the CHEM8M website, and I hope that was helpful to you. Let's just take a moment and marvel at our work, ooh we have seven different signals, one of 'em's gonna show up between 3.2 to five, another one's gonna show up on the higher end of 4.5 to 8.5, another one's gonna show up between 1.5 and 2.6, another one there between four and a half and eight and a half. One is very shielded in the alkane range, and then we have two peaks in the aromatic range, six and a half to nine, and that's seven, great. Okay, so now we want to get a little bit more background on what the parts per million is all about, some other little details I haven't quite gone over. I wanted to really like focus on the, you know, ideas behind chemical shifts, and then how you actually use those tables and really how to do your prelabs. So, here's what the chemical shift is. It's a shift relative to TMS, this is tetramethylsilane, it is the most shielded molecule that we could come up with, as scientists, as chemists, and it has a zero chemical shift and that just means that it has, so it's very shielded, and each of those protons resonate with the magnet at a relative frequency of zero. Once again, that's our standard. So, this ppm, parts per million, just by definition, doesn't actually have a unit, so what we're doing, clean this up here, what we're doing is we are, should be a hertz up here, that's the frequency in hertz or cycles per second, what we're doing here in this example, is we're showing how tert-butyl acetate, so this here is tert-butyl acetate, it is analyzed by proton NMR as follows. It's dissolved in a solution of CDCl three, this is deuterated chloroform, deuterated. It's deuterated meaning that, you know, chloroform is usually CHCl three, if we were to just put CHCl three in there, all you would see is this proton, and it would just overwhelm your spectrum. But that proton can be easily exchanged with deuterium. There is a very very small amount of CHCl three left over, so pretty much any NMR spectrum that you would be seeing, with the exception of this example, you would see a peak for CDCl three show up at about 7.6 parts per million, so pretty much every other spectrum that you'll see in this class, if you see a peak at 7.6 it's not for your compound, it's actually due to your solvent, right? So this is once again, the solvent, that doesn't interfere. It's spiked with a very small amount of TMS so that this peak is very small, it doesn't really inflate your spectrum and make everything else seem really small by comparison. But we use a chemical shift as opposed to giving the units in hertz so that we can run the sample on multiple instruments. So the example below shows that we could take the same example, the same compound on two different instruments, and we end up with the same chemical shifts for both. So here we go, we have, blue, okay, so here's tert-butyl acetate, we have a three hydrogen signal, and a nine hydrogen signal. All nine hydrogens in the tert-butyl group are equivalent, and so we can see over here, that equates to a three and a nine hydrogen signal. Now on the, this is the 60 megahertz, yeah, this is a 60 megahertz instrument. This is the maximum operating frequency of the instrument or of the magnet. The actual resonance frequency of the actual protons in the molecule are millionths of that operating, or of that resonance frequency, so very very very small when I called atoms mini-magnets, I meant they were like really really miniature small magnets in comparison to this big hunk of metal, not real metal, anyway. What we're gonna do, we're gonna calculate the chemical shift and this is starting in units of hertz, so the actual chemical shift, often abbreviated with this delta symbol, is equal to the relative frequency relative to TMS, so, it resonates at a frequency 87 cycles per second greater than tetramethylsilane. We put that over 60 megahertz, the maximum operating frequency of the instrument, the units of hertz cancel, so what we're actually left with is a mega, and the mega stands for a million. And since it's on the bottom, when we do this whole situation, we get 1.45 and then our unit, it's actually unitless, so our unit is actually over 10 to the sixth, and that's really all parts per million are, I'm not sure I define that up above, but ppm, a misleading arrow, ppm, this is parts per million, we put it a little bit more literally you could say, how many parts do you have over 10 to the sixth, or a million? This could be expressed as 1.45 times 10 to the negative six or much easier, 1.45 ppm, you see this is right about where it shows up here, this is 1.45 in terms of parts per million. Now since I'm telling you that it should be, the chemical shift should be the same no matter the instrument, we should already know the answer to this next one. This next spectrum here was run on a 200 megahertz magnet. It has a relative chemical shift, relative resonance frequency of 290, so if we put 290 hertz over 200 megahertz, we get 1.45 over 10 to the sixth, which is exactly the same thing as 1.45 parts per million. So really, parts per million is not unit. It is a relative number, it's just sort of like a ratio, but we can just call it a unit because it looks nice and it's easier to call it a unit. And that's what the ppm's all about, great, so their last example that I have below, is actually kind of a summary, you get a little bit of a look ahead to the future, it's how could we use proton NMR to determine of confirm chemical structures? I've alluded to this in lecture, but I wanted to show you a slightly more complicated example to put together the main components of today's lecture being a chemical shift and integration. Splitting is something that we'll talk more about in a future lecture and beyond, but it's here, and I thought it'd be a good thing to start talking about. So, let's sort of pretend like we don't know this structure just a little bit, and see how much information we can get just from these signals and I'm gonna teach you a little bit more about splitting, so let's pretend that we don't know what that is. What we have first, end up looking at the integration first 'cause that's pretty relatable. The two in this case could stand for two hydrogens, two hydrogens and each of these is three. Now the integration's not always perfect, so sometimes you get 1.97 or maybe it would be 1.9, but it's good enough to round up to two, and typically, you're given more information like you already know what the structure should be or you have a chemical formula from another type of experiment. So that's telling you that it could be, ooh sorry, this could be a CH two group, this could be a CH two group, this could be a CH three group, and that could also be a CH three group, right? So that's what it tells you. We have some other information, let's say we took an IR, an IR spectrum, and it told us that we had a peak around 1700. And the 1700 should be screaming carbonyl, so that tells us that we have proximity to a carbonyl and that you know, at least have one oxygen there in the mix. But we would need to know some other information. We'll notice here, that at four parts per million, we must have an electronegative atom attached to that carbon and since we don't, once again, we do know the actual, we do know the actual structure right now and we're gonna kinda go back and forth and show how we know what's what. So since this is connected to four, or sorry, this shows up at four, this is very deshielded, that must mean, once again, that that carbon is attached to an oxygen. I'm gonna continue on and play with the splitting patterns, I'm gonna make a little bit more space for myself. So splitting patterns, here's the deal. The rule for splitting, splitting, is the n plus one rule. And this is the actual signal splitting. You'll notice up here, this signal is only one peak, in that signal, and that's because it doesn't have any neighboring hydrogens. When you do have neighboring hydrogens, they split via the n plus one rule. Now this means, if you have hydrogens next door, it has to be just next door, then that is going to split the one signal, so instead of this being one signal, one peak rather, it's actually split into four peaks. And we call those four peaks a quartet. The quartet would be the total of the n plus one rule, so that means that n + one was equal to four. If we solve for n, we see, n is three, so the number of neighboring hydrogens was three, meaning this CH two group much be next to a CH three group. But we can try that again 'cause we see, we have yet another quartet on our next peak here, our next signal, and you know, you just kinda roll with this to the best of your ability. So in our next one, we have a chemical shift, we'll say it's around like 2.2, 2.3, and this is what we get when we have a carbon that's next to a carbonyl, and you're welcome to check that out on your table real quick, so we can see carbonyl compounds kinda in the middle in the top, where we have a hydrogen connected to a carbon, connected to a carbon of a carbonyl, that comes in at a range of 1.9 to 3.3. Now as you're maybe thinking, that's kind of a lot to put together, this is something that comes through experience, and also by knowing what you're looking for. So let's say in this particular spectra, you were just told, it would be really helpful if you were told, some way, shape, or form, that this was an ester functional group, so that would give you an indication that this set of hydrogens here, because they have a chemical shift around 2.3, it's next to that carbonyl. Alright, so now we can play with the splitting. We see that this is a quartet, which means it is split by three hydrogens. We have a CH three group next door, so look at that, we have identified this CH two group right there, and this is the signal at 2.2 or 2.3. And we've identified this CH two group, this is the one that showed up at about four, right? Now we have our remaining CH three groups. Let me clean this up a little bit. We have our remaining CH three groups, and both of those CH groups, these are actually two separate signals, these are both triplets. So in a triplet, that means n plus one equals three, so three peaks goes with a triplet, so then n, we solve for it becomes two. If it's a triplet, that must mean we have two neighbors, so each of these methyl groups are connected to CH two groups, which is what we actually see in the known compound. Which is why it's useful to learn knowing the actual answer. These are two CH three groups, they have a very small difference in chemical shift, you can see this one here is a bit more deshielded, and that is likely because that one is closer to the oxygen, right so this is closer to oxygen, which means it's gonna be more deshielded. So this one is farther from the oxygen, farther from the oxygen which means that it is the one that is closer to the carbonyl. And I hope that was useful, remember this last portion about splitting, we're going to be talking about in future lectures, this is just a little bit of a recap of stuff, and also giving you a real glimpse into how NMR can be used to actually figure out the full chemical structure of a compound given little puzzle pieces of integration, chemical shift, and eventually splitting. Once again, thank you for joining me, I hope you all found that useful, and I hope you have a wonderful weekend.