Aromatic protons:

The nmr signals for aromatic protons and carbons take place in characteristic regions of the nmr spectra (generally 6.5-8.0 ppm for ¹Hnmr; 110-160 ppm for ¹³C nmr). Furthermore, it is possible to recognize the substitution pattern of the aromatic ring based upon the chemical shifts of the signals. Tables exist that permit the calculation of the supposed chemical shifts based upon the types of substituents that are present and their relative positions on the ring. In the ¹H spectrum, coupling patterns can frequently be helpful in determining substitution patterns for the aromatic ring. For instance, para-disubstituted aromatic rings often display two signals, both of which are doublets.

In the mass spectra of aromatic compounds there are characteristic fragmentation patterns. For instance, compounds containing monosubstituted aromatic rings generally display fragmentation ions at m/e 39, 50, 51, 52, & 77. Benzylic compounds generally have a strong signal at m/e 91 due to cleavage of a benzylic fragmentation ion.

Because aromatic rings consist of a conjugated π electron system, they can be detected via uv spectroscopy. They usually show an intense absorption close to 205 nm and a less intense absorption in the range 255-275 nm.