So we're talking about the spin-spin coupling mechanism, and we said that because you've noticed that you have multi plats in your spectrum where you expect single lines. And as I was saying ,this is due to the fact that you have other protons, you have other nuclei, in the molecule, and if they have a spin greater than zero then they will behave as magnets as well. So they will either shield or de-shield the external magnetic field, and therefore, the proton that you're observing will come into resonance at different values. So you can have, as we were talking about. Sorry. My pen's here. You have this alpha where you'll de-shield or you can have a beta which acts against a field and therefore, it will shield the external magnetic field. So, we did this, so you have here external magnetic field. Here you have the nucleus you're observing, HA. And here you have the neighboring one, HB. It appears a magnet and here it's the proton we know has two orientations in the magnetic field, up or down. And if it's down, it's actually against the magnetic field, so it will shield it. The field of this proton here, fields, is going to be less because it's shielded. So, therefore, it moves to a lower frequency or a lower chemical shift. If it's the other possibility, where now this proton is up, so it can be up in the alpha position, now it will add to the magnetic field. It's pointing in the same direction, so this nuclei now feels a higher magnetic field. So therefore, remember that Armour possession frequency is directly proportion to magnetic field, so it'll move to a higher frequency. So, it's chemical shift will be bigger. So, in the protons like this, it's gonna have a lower frequency than if there was no other proton there. And in this situation here, it'll be at a higher frequency, a higher chemical share. So that's the origin, this splitting that you see, is due to this effect. So here you have, in terms of the lines, so here, you have this is one H and nucleus without any neighboring interaction. And now, if you have this neighborhood, which you call HB, it's alpha. So, it's aligned with the field, so it de-shields the field. So, you get it to higher frequency or higher chemical shift. And then the ones that are against the field, Beta get a lower one. So instead of a single line, like you might expect, you get a double. You get a splitting. We're just talking about one nucleus, but you consider a large number of molecules. [COUGH] The number of ones having alpha and beta is about the same. Remember, we said that there's a slight excess of alpha spins, because it's like a law of energy but they're generally about 50/50. So you'd have 50% of alpha. So there's a 50% of this occurrence, 50% of that occurrence. So what you get then, is you get two lines of 50% intensity instead of one line at 100%. And this is what causes splitting in the peaks that you observed. Right. So lets go back to our example we had, this 1,1-dichloroethane, and if we look at this peak here, we said this was due to this proton here. Sorry, we didn't say that, we said something else, didn't we? We said that this was do to this, these protons here. It's got the lower chemical shift, and now what you can see, it's split into two. And the reason it's split into two is because of the interaction with this one here. This one can be 50% of the time up that way. And they can be another 50% of the time down that way. So this one here when it's up this way, it would feel as if it were this way so external field. So then that will de-shield it, so you shift it to a higher chemical shift, so that's the slide here. This one while against it 80% of the time, it will push it down here a bit. And the splitting it up. We mention 6 hertz and this is the chemical shift and you measure the chemical shift as the center of the two. So that's basically what I said there. So what about this peak? Now with this peak at 5.89, that's centered. So centered at 5.89. You can see that that's got even more splitting. That's got a pattern four lines. It's got one, three, three, one. So what's going on there? Now [COUGH] what this hydrogen sees, we're talking about this nucleus, this state, we're looking at. A particular environment here. It now, of course, has three equivalent protons in its neighbor, not just one. So each of these are going to be either aligned with the field or against it. So what that means, it's going to be a little bit more complex, the situation that exists than when you just have a single hydrogen there. So what you've got to work out is, you've got to work out what are the possibilities for this, for these three protons. And you can go through the arrangements that they can take in the magnetic field, again the zero is here in this direction, so you can see if they line up with the field, or we call Alpha, you can have the three of them lining up with the field. So that's one possible way. You can then have these two lining up and this one against, or you have what you call equivalent possibilities where you'll have two alpha situations and one beta situation. Again, you can go down when you turn them over, you can have the three betas. That's just one possibility. But when you have two beta and one alpha, you again have three possibilities. So all together, well, you have eight possible orientations for the spins that you can work out. And this one is 1/8, where you have say either the three lined up with the field, or you have the three lining against the field. In this situation here, where you have two alpha and one beta, you can see that they occur at three time. So there's a higher probability of these occurring. That's because there's more orientations you can work out. So what you should see now, is that these situations here will de-shield, because they're lining up with the fields, so the effect of the field at the proton you're observing sees is going to be greater than the external field. It's gonna be greatest isn't it, on this occasion, because there's three of them lined up. So that's going to be shifted to the highest frequency. But in this situation here, you have two [COUGH]. >> [INAUDIBLE] >> [INAUDIBLE]. >> Okay, all right. It's okay. Seems to be one of these days. Isn't it really, yeah? So you have two here lined up with the field, and you have one against. So they are going to give you, you see that that's going to give you same shift. These three possibilities are going to give you the same shift. Here, well, let's go down to the bottom one here. You have the betas lined up against the field. So they're going to shield the nucleus cuz they are going to decrease the effective field that the nucleus sees, and three of them is going to do it the most. Whereas when you have just two of them, against two of them and that is suppose one here, the net shielding is going to be less but these three situations are going to be the same. Okay. So, what that is going to do, you should realize that now you are going to, there is four peaks. And this is where the four peaks come from. Due to the [INAUDIBLE] equivalent, hydrogens. So you've got one, two, three, four and also we said the intensity was one, three, three, one. And it's because you have three, the probability is three here for these situation as opposed to one for the two other ones. Move on. So now, if you look at the line, how it splits, here you would have the situation without that interaction with the CH3 group. And now, when they line up with the field they increase the field, so this is where the three spins are lined up with the field, so you get the largest chemical shift for this one, and then you get the three different possibilities we had. This is when the shielding and the de-shielding, this is when net shielding. This is when you have the three protons lined up against the field and therefore, they shield the proton from the field. So what you get, so overall 1/8 will be three beta 3/8 will be two beta, etc. And therefore we get a quartet with the intensities 1:3:3:1. So that's what gives the multiplet structure in the spectrum. So here now we have, we can explain this spectrum. We can explain in terms of chemical shift, which is the central peak position, but also now we have this fine structure. And that we can explain for this one, to this, I keep saying that. It's due to these protons here being split in two by this one. And this quarter structure is from this proton here, been split into four by the interaction with three equivalent protons. So the three currently equivalent hydrogens is CH3 send a single hydrogen atom to the peak, into a doublet. A single hydrogen CH3 chemically equivalent to hydrogens. So it's 1:3:3:1. So, what you can generalize from that, you can go through different examples. You can go up to four, five, six protons, and you could work out all the different possibilities for the alignment of the spins, and you come up with the patterns that you observe. So the presence of any equivalents, what you gotta remember the rule is, if you have any equivalent atoms, what you will get is N + 1 lines. So if you have one hydrogen, one attraction, you get two lines. If you have two, you get three lines. If you have three, you get four lines. If you have five, you get six lines and so on. So that's the number of lines you get in the splitting. And then, this actually comes from probability theory called Pascal's Triangle. So here's N, the number of nuclei. Zero. You have one. Then if you have one nucleus you have two lines and the intensity ratio will be 1:1. Two protons, interacts 1:2:1. Three.:3:3:1. Four, 1:4:6:4:1. So this is based on this probability theory. So that's how you work out the number of lines. Okay. So let's just take a simple example of ethanol spectrum here. So you have the OH group, and you have CH2, and you have the CH3. So now, based on our knowledge, you have three chemically equivalent CH3 groups. And they see two hydrogen atoms in the CH2 group. So the CH3 peak will split into a triplet, 1:2:1. So you have three lines there, the ratio 1:2:1. And then the CH2 spectra, a little bit noisy so it's not that clear, but the CH2 group, it won't interact with the OH group here. Because if you prepare it in OH group exchange very quickly, so you don't actually get observed coupling from the OH group. If you do observe coupling with the CH3 groups or your three equivalent protons. So, it'll spread the CH2 resonants into 1:3:3:1. And the OH group, sometimes you'll observe it, but it's rapidly exchanging so it's not it's not involved in this spin, spin, spin, spin, spin. And, so as I said the hydroxyl and hydrogens [INAUDIBLE]. So, again, this is what your looking for in patterns. Some of you in your workshops today, you were given some patterns from real spectra and you're asked to try to work out what the interactions giving rise to these patterns are. So basically, that's pretty much it in interpreting any more spectra. You need to know the chemical shift. And you should now be able to at least. You're not gonna be able to assign spectra as experts. But you should know, like, in this simple molecule, here, ethanol. You know that's a CH3 group. If you look up tables is going to have a shift of about 1.0. CH2 near an OH group is gonna have a shift of about 4.0. And the OH is around 5.0 here. And again, you can interpret this easily in terms of the electron density. At the particular nuclei, you'd expect the least. The most least electron density would be the hydroxyl group because the oxygen is directly bonded to it, oxygen is quite electro negative. So it pulls electrons off it so it's de-shield. It's got a high chemical shift value. Then the protons on the CH2 group are nearest to the OH group, so they'll be the next effective, and they've got a fairly higher chemical shift value and then the methyl group is fairly trail removed from the OH group. So, it has the lower chemical shift. So, that's one key parameter you'll work out from in your spectrum. And in the other ones are the splittings that we've just been talking about. So they're the main parameters. In the later years, you probably will talk a little bit about more advanced NMR in a minute, very briefly, but these are the measurements that you have to make from an NMR spectrum, no matter how you record it or how complex the system is. It's the chemical shift and the spin spin splitting, so at this stage what you want to get is make sure that you have a good understanding on how these arise. And then the rest is just experience in the science spectra. Looking into more advanced techniques of measuring the spectra.