(Note : in this 3rd example, the middle CH₂ (black) at about 2 ppm seems to appear as a hextet (6 lines) due to a total of 5 neighbours since 3 + 2 = 5: this is due to an important approximation that helps "simplify" the spectra. The approximation allows us to assume that the CH₃ (green) and the other CH₂ (blue) are "similar" neighbours and that the coupling constants involved are the same (i.e. the coupling constant of the middle CH₂ (black) to each of the other groups is essentially the same. This is reasonable expectation because (1) both the other groups are sp3 C systems and (2) there is free rotation of the chain. If this approximation doesn't hold or apply, then more complex coupling patterns are observed (see later).