Theory of Nuclear Magnetic Shielding in Molecules. I. Long-Range Dipolar Shielding of Protons

The general nuclear magnetic shielding theory of Ramsey is developed for the case of ``long-range'' nuclear shieldings. Such shieldings arise from the magnetization induced in molecular electrons localized to groups one or more bond lengths removed from the shielded nucleus. Order-of-magnitude calculations indicate that these long-range shielding fields can make significant contributions to proton chemical shifts in, for example, aromatic hydrocarbons and alkyl halides.