mesomeric effect

This term is a specialized technical expression used almost exclusively in organic chemistry and molecular orbital theory. It describes the resonance-driven shift of electrons across a system of alternating single and double bonds, which alters the electronic properties of the molecule.

In a professional academic context, it is often used interchangeably with the term resonance effect. However, the mesomeric effect specifically emphasizes the influence of a substituent group on the electron density of a conjugated system, typically categorized as positive (+M) for electron-donating groups or negative (-M) for electron-withdrawing groups.