[shafaifer]

Is it correct that one can determine that a ring is trisubstituted if one can see 3 lower peaks and 3 higher peaks in a ¹³C spectrum? Also, is it correct, to determine the respective positions on the ring one would have to calculate the coupling constants?

I have asked a question like this earlier without answers - please do not find me greedy when I talk like this; I have looked this up elsewhere and with my recent investigation I have not found anything, so I hoped you could help.  You could say I should look better but this is just a matter of time (perhaps plenty). Great exellencies like you were once students I assume; did knowledge come naturally easy to you?

[OrgXemProf]

After I finally discerned that "3 lower peaks and 3 higher peaks" refer to peak intensities rather than to upfield (higher) vs. lowfield (lower) absorption signals in ¹³C NMR spectra, then an aspriring great excellency like myself finally achieved nirvana, of a sort.

Indeed, the three ring carbon atoms in a trisubstituted benzene that bear attached hydrogens experience Overhauser enhancement; these are the "higher peaks" in the spectrum. By way of contrast, the three ring carbon atoms that bear substituents other than attached hydrogen do not experience Overhauser enhancement (at least, not to the same degree as directly bonded C-H carbons), and these correspond to the "lower peaks" in the spectrum.

For an example, see the proton noise-decoupled carbon-13 NMR spectrum of 2-bromo-5-chlorotoluene: (onlne reference: http://sdbs.db.aist.go.jp/sdbs/cgi-bin/direct_frame_top.cgi - see Spectrum No. 2318).

As an aside, I warmly recommend that you drop the attitude when you request assistance from Forum members, as this adjustment is likely to serve you well by earning you a bit more respect in the future.

[shafaifer]

Thank you very much, Proffesor. In the future I will express myself more accurately, I should say.