How should I label the multiplicity of the aromatic signals in an 1H-NMR spectrum with the following substitution pattern?
I have seen lots of people labeling both signals in this kind of system as doublets, probably because the resolution of the spectrum was not high enough, or because we are often told, these look like doublets. However, what looks like a doublet doesn't necessarily have to be one and thus, should not be called doublet, because it doesn't reflect the actual couplings in this system:
- The ortho-coupling (3J) for both signals should be about 6.0 and 9.0 Hz.
- The meta-coupling (4J) for both signals should be between 0.9 and 3.0 Hz.
- The para-coupling (5J) for both signals should be between 0.0 and 1.0 Hz.
(These numbers are from the Hesse-Meier-Zeeh, a German textbook about spectroscopy in organic chemistry).
I am inclined to call these signals multiplets rather than doublets, because I can only guess the coupling constants, especially for the right signal at about 7.36 ppm.
Or is it good practice to call them pseudo-doublets? And what would be the symbol (like s for singlet, d for doublet, etc.)?