Which among the following is incorrect statement?

We need to identify the incorrect statement about the electromeric effect.

Option 1: "Electromeric effect dominates over inductive effect." This is correct. The electromeric effect, being a complete transfer of $$\pi$$-electrons, is generally stronger than the inductive effect, which is a partial displacement of $$\sigma$$-electrons.

Option 2: "The electromeric effect is a temporary effect." This is correct. Unlike the inductive effect (which is permanent), the electromeric effect occurs only when an attacking reagent approaches the molecule. It is a temporary polarization of $$\pi$$-bonds.

Option 3: "Hydrogen ion (H⁺) shows negative electromeric effect." This is INCORRECT. H⁺ is an electrophile (electron-deficient species). When H⁺ attacks a $$\pi$$-bond, the $$\pi$$-electrons shift toward the attacking reagent — this is a positive electromeric effect (+E), not negative. The negative electromeric effect ($$-E$$) occurs when the attacking reagent is a nucleophile, and the electron pair shifts away from the attacking species.

Option 4: "The organic compound shows electromeric effect in the presence of the reagent only." This is correct, consistent with the temporary nature of the effect.

The incorrect statement is Option (3).