[Sona]

13-CNMR of p-dicyanobenzene gives 3 singlets. 132ppm, 119ppm and 117 ppm. Which one for which C? Aromatic C range is 110 to 170 ppm and C≡N range is 110 to 120ppm. Now from these three data given I cannot understand which one is for C≡N and which one for C attached to C≡N and which one is for other unsubstituted Cs of aromatic ring?
please help.

[wildfyr]

This website is a great source for free NMR prediction: https://www.nmrdb.org.

I plugged it in to the software and it gave: 132 is the C-H, 118 is the C of the cyano and 112 is the C-CN of the rings. Not exactly cut and dry, but its fair to assume that the trend is the same. Most of the time I would be content to leave it at this.

To assign them with full confidence you probably need 2D ¹³C-¹³C NMR (INADEQUATE?). Or perhaps you could tell with a very long run of a real life 1D ¹³C. The C on the ring would give more signal than the cyano since its has closer connectivity to a hydrogen. Or perhaps some version of a coupled spectrum 1D ¹³C would reveal the aryl carbon.

Maybe someone with more experience has a simpler answer.

[kriggy]

You could easily asign the ring carbon by running APT (you see which one has proton attached). Then you might get lucky with some 2D experiments. HMBC probably wont work because all protons would have interaction with the aromatic quarternary carbon, but maybe? Also is there something like C-H noesy? Or some C-N 2D experiments but those might be pretty difficult to run