Question

Explain +R and -R effect with suitable example?​

Answer 1

The +R effect or positive resonance effect is expressed by the electron donating groups (for eg. –NH2, -OH, -OR etc) which release electrons or donate electrons to the rest of the molecule by delocalization of electrons within the molecule.

-R effect or Negative resonance effect occurs when the groups withdraw the electrons from other molecules by the process of delocalization. The groups are usually denoted by -R or -M. In this process, the molecular electron density is said to decrease. For example- -NO2, C=O, -COOH, -C≡N.