Question

Which of the following statements are TRUE?
(I) Inductive effect operates through the sigma bond
(II) Resonance effect operates through the pi bond
(III) Inductive effects operate through the pi bond
(IV) Resonance effect operates through the sigma bond

• A. (I) and (II)
• B. (II) and (III)
• C. (III) and (IV)
• D. (I) and (IV)

Hint:

The inductive effect moves sigma electrons, while the resonance effect moves pi electrons.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Electron displacement effects decide how charge is spread in an organic molecule. Two key ones are the inductive effect and the resonance (mesomeric) effect.

Step 2: Inductive effect.
It is the permanent shift of electrons along a chain of sigma bonds because of an electronegative atom or group. It works through sigma bonds only. So (I) is TRUE and (III) is FALSE.

Step 3: Resonance effect.
It is the delocalisation of pi electrons or lone pairs through a conjugated system. It works through pi bonds and not sigma bonds. So (II) is TRUE and (IV) is FALSE.

Step 4: Pick the pair.
The true statements are (I) and (II), which is option (A). Options (B), (C) and (D) each include (III) or (IV), which are false.

Final Answer:
Inductive effect travels via sigma bonds, resonance effect via pi bonds. \[ \boxed{\text{(I) and (II)}} \]