Question:
Which of the following group shows $-R$ effect?
Which of the following group shows $-R$ effect?
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Groups with multiple bonds to electronegative atoms (like $-CN, -NO_2$) show $-R$ effect.
Updated On: Apr 24, 2026
- $-OH$
- $-OCOR$
- $-NH_2$
- $-CN$
- $-OR$
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The Correct Option is D
Solution and Explanation
Concept:
Resonance effect:
• $+R$ effect: Electron donating via resonance
• $-R$ effect: Electron withdrawing via resonance
Step 1: Identify group behavior.
• $-OH, -NH_2, -OR$ $\rightarrow$ $+R$ (electron donating)
• $-OCOR$ $\rightarrow$ weak $+R$
• $-CN$ $\rightarrow$ strong $-R$ (electron withdrawing)
Step 2: Select correct group.
\[ -CN \text{ shows } -R \text{ effect} \]
• $+R$ effect: Electron donating via resonance
• $-R$ effect: Electron withdrawing via resonance
Step 1: Identify group behavior.
• $-OH, -NH_2, -OR$ $\rightarrow$ $+R$ (electron donating)
• $-OCOR$ $\rightarrow$ weak $+R$
• $-CN$ $\rightarrow$ strong $-R$ (electron withdrawing)
Step 2: Select correct group.
\[ -CN \text{ shows } -R \text{ effect} \]
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