Chemistry Q63 – JEE-MAIN 2026

Home Chemistry Basic Organic ChemistryQuestion #102

Increasing order of electron withdrawing power of following functional groups is: a. - CN b. - COOH c. - NO

_{2}

d. - I

Clue 1 of 3: Electron-Withdrawing Groups (EWG)

Electron-withdrawing groups decrease electron density in a molecule, primarily through inductive (-I) and resonance (-M) effects.

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Step 1: Identify Electron-Withdrawing Effects for Each Group✦ Active

The electron-withdrawing power of functional groups is determined by their inductive ( $- I$ ) and mesomeric ( $- M$ ) effects. Let's analyze each group:

a. -CN (Cyano group): Exhibits a strong $- I$ effect due to the electronegative nitrogen and a moderate $- M$ effect due to the triple bond.

b. -COOH (Carboxyl group): Exhibits a moderate $- I$ effect due to the electronegative oxygen atoms and a weak $- M$ effect due to the carbonyl group.

c. -NO $_{2}$ (Nitro group): Exhibits a strong $- I$ effect due to the electronegative oxygen atoms and a very strong $- M$ effect where it withdraws electrons through resonance.

d. -I (Iodo group): Exhibits a weak $- I$ effect due to its electronegativity. Halogens also have a $+ M$ effect, but their $- I$ effect is considered for EWG comparison, and it's the weakest among the given options.

Step 2: Compare Relative Strengths of Electron-Withdrawing Groups○ Expand

Based on the combined inductive and mesomeric effects, the general order of electron-withdrawing strength is:

- N O_{2} > - C N > - C O O H > - I

The nitro group ( $- N O_{2}$ ) is generally considered one of the strongest electron-withdrawing groups due to its powerful resonance and inductive effects. The cyano group ( $- C N$ ) is also strong, followed by the carboxyl group ( $- C O O H$ ). The iodo group ( $- I$ ) is the weakest among these due to its relatively weak inductive effect.

💡 Teacher's Secret Hint

Remember that resonance effects often dominate over inductive effects when both are present and significant.

Step 3: Arrange in Increasing Order○ Expand

Arranging the functional groups in increasing order of their electron-withdrawing power:

- I < - C O O H < - C N < - N O_{2}

Translating this to the given labels (a, b, c, d):

d < b < a < c

This order matches option 3.

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Chemistry Question 63 – JEE-MAIN 2026

Clue 1 of 3: Electron-Withdrawing Groups (EWG)

🧠 Full Solution Path