Question

Which of the following effects involves the delocalization of pi electrons in a molecule?

• A. Inductive effect
• B. Resonance effect
• C. Electromeric effect
• D. Hyperconjugation

Hint:

Delocalization of pi electrons or lone pairs across a conjugated system is the resonance effect.

Answer 1

The Correct Option is B

Step 1: Look for Pi Electrons
Only effects that act on pi electrons or lone pairs are candidates: resonance and electromeric.

Step 2: Permanent versus Temporary
The electromeric effect is temporary and appears only in the presence of a reagent, whereas resonance is a permanent delocalization.

Step 3: Result
The answer is option (B).

Final Answer:
Resonance is the effect that delocalizes pi electrons. \[ \boxed{\text{(B) }\text{Resonance effect}} \]