NMR splitting patterns?

Can anyone explain to me what they are and how to determine them for a simple organic compound?NMR splitting patterns?
An isolated nucleus resonates at one specific frequency which depends on the local magnetic field, which depends on the surroundings. But if there is another nucleus nearby, the current magnetic state of that second nucleus can slightly modify local magnetic field of our nucleus. If we're talking hydrogen, half of all molecules will resonate slightly above and half slightly below its original resonance, turning the original peak into two peaks, aka splitting a singlet into a doublet.





The interaction that causes splitting is carried through chemical bonds.In a typical 1H-NMR spectrum of a typical organic compound, significant splitting is observed for three-bond connectivities, i.e. every time there is a H-C-C-H fragment, the resonance of the first hydrogen is split in two (and so is the resonance of the second hydrogen). Splitting is measured in hertz. Three-bond coupling results in splitting between 0 and 14Hz, depending on the torsion angle of the H-C-C-H fragment. Average number for average alkanes is 7 Hz.





Two-bond connectivities, such as H-C-H result in splitting of about 10-14Hz, except if the interacting hydrogens have identical chemical shifts, splitting is not observed for complicated reasons..





Four-bond coupling, H-C-C-C-H and above are typically less than 1 Hz (unless there's some aromaticity/conjugation going on), and in most textbook examples they are not used.





Now if there are two nuclei that are both three bonds away, the splitting happens on both of those. Original singlet becomes a doublet because one of those two hydrogens can affect its resonance, and then each component splits into a doublet of its own because of the splitting effect of the other hydrogen. This can make four peaks (splitting pattern called ';doublet of doublets';) or three peaks if the middle components overlap (splitting pattern called ';triplet';). You will see triplets when splitting on two identical nuclei, such as in H-C-CH2.





If there are three identical hydrogens all three bond away from our hydrogen,, its signal splits into 4 peaks (splitting pattern called ';quartet';), and so on. And this is barely scratching the surface. There are books written about spin-spin coupling.