Resonance Effect: The polarity produced in the molecule by the interaction of two pi bonds or between a pi bond and lone pair of electron present on an adjacent atom.
(i) Positive resonance effect: In this effect, the transfer of electrons is away from an atom or substituent group attached to the conjugated system. The atoms of groups which show + R effect are halogens, -OH, -OR, -NH2 etc.
(ii) Negative resonance effect: In this effect, the transfer of electrons is towards the atom or substituent group attached to the conjugated system. The atoms or groups which dhow -R effect is -COOH -CHO, -CH etc.
