Final answer:
The magnitude of the deshielding effect decreases as the distance from the electron-withdrawing substituent increases. Deshielding is important in understanding the magnetic field experienced by nuclei in nuclear magnetic resonance (NMR) spectroscopy. The effect is most pronounced when the electron-withdrawing group is close to the nucleus and diminishes with increasing distance.
Step-by-step explanation:
The magnitude of the deshielding effect decreases rapidly as the distance from the electron-withdrawing substituent increases. Deshielding refers to the reduction in electron density in the vicinity of a nucleus, caused by the presence of electron-withdrawing groups or atoms. As a result of increased deshielding, nuclei can experience a greater magnetic field and hence give rise to different chemical shifts in nuclear magnetic resonance (NMR) spectroscopy. Conversely, as the distance between the nucleus and the electron-withdrawing group decreases, the deshielding effect becomes stronger, profoundly impacting NMR signals.
For example, in a molecule like chloroform (CHCl₃), the hydrogen atom experiences significant deshielding because of the electronegative chlorine atoms. As the distance between a hydrogen nucleus and the chlorines increases, the deshielding effect weakens, and the peak corresponding to the hydrogen would appear at a higher field (or lower chemical shift) in an NMR spectrum.