Final answer:
The NMR signal for benzene with one substituent reflects the influence of the substituent on the hydrogen atoms of benzene, and this can cause changes in the chemical shifts of the aromatic protons. Naming involves placing the substituent as a side chain on the benzene, with positional numbering used for multiple substituents.
Step-by-step explanation:
An NMR (Nuclear Magnetic Resonance) signal for benzene with one substituent typically presents a pattern that reflects benzene's symmetrical structure. In its simplest form, benzene has a chemical shift in the range of 7.26 to 7.44 ppm due to its six hydrogen atoms being equivalent. When a substituent is introduced, it can influence the electronic environment of those hydrogens and the chemical shifts of the aromatic protons will vary based on the nature of the substituent. For monosubstituted benzene, there can be three different types of protons (ortho, meta, and para to the substituent), and these will usually display distinct chemical shifts. Ortho protons (adjacent to the substituent) tend to resonate downfield (at a higher ppm) compared to the meta and para protons because of the substituent's electron-withdrawing or donating effects.
When naming substituted benzene molecules with a single substituent, the substituent is named as a side chain on a benzene, such as methylbenzene for toluene. Additionally, a benzene ring missing a hydrogen atom, known as a phenyl group, can itself be a substituent, as in the molecule 2-phenylbutane. If there are two or more substituents, positions on the benzene ring are numbered to give the lowest possible numbers to the substituents, with relative positions indicated using terms like ortho (1,2-disubstitution), meta (1,3-disubstitution), and para (1,4-disubstitution).
Furthermore, the presence of a substituent on a benzene ring can give rise to various derivatives of benzene, where aromatic compounds undergo substitution reactions rather than addition reactions. This underscores the importance of a correct depiction of the substituents on a benzene molecule in understanding its NMR spectrum and overall chemical behavior.