 Oh, here's a little bit of a quick cooked tour through nuclear magnetic resonance and it's a little bit tricky. So let's just see if we can accept a few things and move on to the analytical stage. The important thing is that what we've looked at in spectra up to this point is the movement of electrons. So electrons moving from a grand state to an excited state and they do that by taking in a certain amount of electromagnetic radiation. This time when we're looking at nuclear magnetic resonance and really the name is the clue to exactly what's going on here, we're not looking at the electrons now, we're looking at the nucleons that is the protons and the neutrons in the nucleus and how they respond to an external magnetic field. The underlying physics associated with this is really quite complex and involves really more quantum level understandings which I do believe are beyond the scope of the chemistry course. Nevertheless, if we can accept a few things a little bit on faith and by all means have a look at these in a bit more detail to go into a bit more depth, particularly if you're also doing physics because I think the two things will dovetail together very very nicely. But what we want to understand is that the nucleus of an atom will display this concept or this property of spin if it has an odd mass number and this is one of the reasons why we look at proton NMR and we also look at carbon 13 NMR. We do know or hopefully we do know that the most common isotope of carbon is carbon 12 but carbon 12 would be an even numbered mass for the nucleus of carbon so we can't use it. It doesn't show the effects that we want so we need to use carbon 13. The concept is that atomic nuclei act like small bar magnets and this is a physics property where we look at the interaction between electricity and magnetism and that is if we have moving charges they can generate a magnetic field and induce a magnetic field and of course if we change magnetic fields we can induce a current so these two things, Earthstead and Faraday's discoveries are applicable right at this tiny level as well. There are some limitations and some generalized assumptions that we're making here but if you just think about the fact that little charged particles can create by their movements small magnetic fields and we've kind of explained this in terms of things like domains when we've talked about the magnetic properties of certain types of elements for example iron. So the principle is if these little moving charges can create little tiny magnetic fields then they can act like little tiny bar magnets that is they can line up in terms of the north and the south pole and therefore if we place an external magnetic field around these nuclei then the magnetic fields will align they'll either be directly aligned to the magnetic field so in the same orientation and that's the lower energy one or they'll oppose the magnetic field so they'll be exactly back to front if you like so in terms of them aligning with the north south pole if they're aligned to the external magnetic field then they are at low energy and if they're opposed then they'll be at a higher energy and so the higher energy because they'll want to rotate in order to return to that sort of more ground more stable state so electromagnetic radiation can be absorbed obviously it's more likely to be absorbed by those at a lower energy state that can then flip into that higher energy state in the same way that we've said the electrons can absorb energy to go from a ground state to an excited state in terms of their orbital shell movement now if this was the only thing that happened then that would mean that every hydrogen one nucleus and every carbon-13 nucleus would all give off exactly the same pattern because they would set in a similar thing or at least they'd be close enough that there'd be very little difference between them the problem is that with electrons on the outside electrons are charged particles these are charged particles that are moving they will also have magnetic fields associated with them they're much smaller mass so there will be a difference in the strength but nevertheless this disrupts the patterns that we are likely to see and that disruption gets magnified depending on how those electrons are distributed i.e. what they're bonding to so are they bonded to double bonds are they in a high region of electron density are they bonded to oxygens is there a difference in electronegativity that's creating levels of polarity there's lots of different options that we can have and those are reflected in the different functional groups that we have particularly around those carbon atoms and so that's what produces these different patterns of NMR outputs that we see it's a little bit over simplified I am aware of that but and it's definitely worth having a little bit of a look I can recommend a resource called spectroscopy in a suitcase I think that's a really nice pictorial representation of a lot of these different types of spectra that are really useful to get a little bit more detail and obviously there's a huge amount of stuff on the internet about this type of chemistry or physics and so you can go into it heaps and heaps of detail but the main thing that we want to do is we want to know how to apply the technique of NMR