Mesomeric effect involves

Step-by-step solution

Resonance or mesomeric effect is defined as, the polarity produced in the molecule by the interaction of two -bonds or between a -bond and a lone pair of electrons present on an adjacent atom. There are two types of mesomeric effect. +M effect is observed when direction of electron displacement is away from an atom or substituent group attached to the conjugated system e.g., - halogen, - OH ,- NH ₂ etc. On the other hand, - M effect is observed when the transfer of electrons is towards the atom or substituent group