Question

Which among the following is incorrect statement?

• A. Electromeric effect dominates over inductive effect
• B. The electromeric effect is, temporary effect
• C. The organic compound shows electromeric effect in the presence of the reagent only
• D. Hydrogen ion (\( \text{H}^+ \)) shows negative electromeric effect.

Answer 1

The Correct Option is D

Understanding the Electromeric Effect:

The electromeric effect is a temporary effect observed in organic compounds, where the complete transfer of a shared electron pair occurs in the presence of an attacking reagent. It is often observed in compounds with double or triple bonds and only lasts as long as the reagent is present.

Explanation of Each Statement:

Statement (1): Electromeric effect does dominate over the inductive effect when a reagent is present, as it involves the complete shift of electron density, which is stronger than the partial electron shift seen in the inductive effect. This statement is correct.

Statement (2): The electromeric effect is indeed a temporary effect that occurs only in the presence of an attacking reagent. Once the reagent is removed, the electrons revert to their original position. This statement is correct.

Statement (3): The electromeric effect is observed only when an attacking reagent is present, causing the shift of electron density. This statement is correct.

Statement (4): Hydrogen ion (\( \text{H}^+ \)) shows a positive electromeric effect because it attracts electron density toward itself due to its positive charge. Thus, it does not exhibit a negative electromeric effect. This statement is incorrect.

Conclusion:

The incorrect statement is Option (4): Hydrogen ion (\( \text{H}^+ \)) shows a negative electromeric effect.

Answer 2

Step 1: Understanding the Electromeric Effect.
The electromeric effect is a temporary electronic effect where the electron pair in a pi bond is completely transferred to one of the atoms in the bond due to the attack of a reagent (electrophile or nucleophile). It only occurs in the presence of an attacking reagent and vanishes once the reagent is removed.

Step 2: Types of Electromeric Effects.
- +E Effect: The electron pair is transferred towards the attacking reagent (usually electrophile).
- −E Effect: The electron pair is transferred away from the attacking reagent (usually nucleophile).

Step 3: Role of \( \text{H}^+ \) (Hydrogen Ion) in Electromeric Effect.
The hydrogen ion (\( \text{H}^+ \)) is a positively charged electrophile and, when it attacks a double bond (like C=C), it induces a +E effect by shifting the electron pair towards itself.

Step 4: Assessment of the Statement.
The statement "Hydrogen ion (\( \text{H}^+ \)) shows negative electromeric effect" is incorrect because:
- \( \text{H}^+ \) being an electrophile causes a positive electromeric (+E) effect, not a negative one.
- Negative electromeric effect (−E) occurs when nucleophilic reagents are involved.

Step 5: Conclusion.
Thus, the incorrect statement among the options is:
\[ \boxed{ \text{Hydrogen ion (} \text{H}^+ \text{) shows negative electromeric effect.} } \]