Final answer:
Protons of benzene derivatives in ¹H NMR spectra appear at chemical shifts > 5 ppm due to the deshielding effect of delocalized electrons in the aromatic ring. The presence and position of substituents can further influence these shifts, with NOESY providing spatial relationship data.
Step-by-step explanation:
The protons of benzene derivatives typically appear downfield in ¹H NMR spectra, specifically at chemical shifts greater than 5 ppm. This is primarily due to the deshielding effect of the aromatic ring's delocalized electrons which causes the hydrogen atoms attached to the benzene ring to resonate at lower fields. In the case of substituted benzene derivatives, the precise chemical shift of each proton can be influenced by the nature of the substituent and its location on the benzene ring. Electron-withdrawing groups, for example, can deshield the proton even further, leading to a downfield shift. Conversely, electron-donating groups can result in an upfield shift.
Furthermore, the use of spectral techniques like Nuclear Overhauser Effect Spectroscopy (NOESY) can provide additional information about the spatial relationship of the protons, aiding in the assignment of the relative configuration of the molecules. For instance, a positive Nuclear Overhauser Effect (NOE) indicates that the protons in question are in close proximity.