Pi Electron Shielding in NMR Shifts

Pi electrons in organic molecules can change NMR chemical shifts when an applied magnetic field makes them circulate. This circulation creates an induced diamagnetic field over a large region. When molecules tumble in solution, spherical substituents produce a zero net field. Non-spherical substituents do not, so the net eff...

An applied magnetic field causes loosely bound π electrons to circulate, producing a local or induced diamagnetic field over a large spatial volume.

The effect of the induced field depends on the orientation of the molecule with respect to B₀, resulting in diamagnetic anisotropy.

In alkenes, the applied field is reinforc...