I recently carried out a Buchwald–Hartwig reaction to attach a morpholin-4-yl group to an aromatic ring:
In the proton NMR of the (columned) product, I found the peaks corresponding to the morpholine protons. The multiplet at 3.86 ppm comes from the protons next to oxygen, and the protons next to nitrogen give rise to the multiplet at 3.04 ppm:
The spectrum was obtained on a 400 MHz spectrometer and the values of the "coupling constants" are shown in the second multiplet. (They are identical in the first one.)
Why do the peaks have the fine structure that they do? Based on a simplistic analysis (the "n+1 rule"), I would expect a 1:2:1 triplet for both of these peaks.
In my crude NMR (pre-column) there was some excess morpholine and those peaks had exactly the same fine structure.
Does it have something to do with the chair conformation of the six-membered ring and the differentiation between axial and equatorial protons?