Inductive Effect DPP for NEET & JEE

Inductive Effect DPP (NEET & JEE)

20 High-Yield PYQ-Based MCQs | JEE Main, Advanced & NEET Level

Inductive Effect Cheat Sheet:
• Electron-withdrawing (–I): –NO₂ > –CN > –COOH > –F > –Cl > –Br > –I > –OH > –NH₂
• Electron-donating (+I): Alkyl groups: (CH₃)₃C– > (CH₃)₂CH– > CH₃CH₂– > CH₃–
• Effect decreases with distance: Strong at α, weak at γ
• Explains: Acidity, basicity, reactivity, dipole moment

1. [JEE Main 2023] The correct order of acid strength is:

a) CH₃COOH > CH₂ClCOOH > CHCl₂COOH > CCl₃COOH
b) CCl₃COOH > CHCl₂COOH > CH₂ClCOOH > CH₃COOH
c) CH₃COOH > CH₂ClCOOH > CCl₃COOH > CHCl₂COOH
d) CHCl₂COOH > CCl₃COOH > CH₂ClCOOH > CH₃COOH

JEE Main 2023 | 8 April Shift 1

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Answer: b) CCl₃COOH > CHCl₂COOH > CH₂ClCOOH > CH₃COOH

Explanation: –Cl is –I group. More Cl atoms → stronger electron withdrawal → stabilizes COO⁻ → increases acidity.
• CCl₃– → 3 Cl (strongest –I)
• CHCl₂– → 2 Cl
• CH₂Cl– → 1 Cl
• CH₃– → +I (weakest acid)

2. [NEET 2022] Which has the highest boiling point?

a) CH₃CH₂CH₂Cl
b) CH₃CH₂CH₂CH₂Br
c) CH₃CH₂CHBrCH₃
d) (CH₃)₃CCl

NEET 2022 Phase 2

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Answer: b) CH₃CH₂CH₂CH₂Br

Explanation: Boiling point ∝ molecular weight + polarity.
• All have similar chain, but Br > Cl in mass.
• –Br and –Cl both –I, but mass dominates.
• n-Butyl bromide: highest MW → highest BP

3. [JEE Adv 2021] The correct order of basic strength is:

a) CH₃NH₂ > (CH₃)₂NH > (CH₃)₃N > NH₃
b) (CH₃)₃N > (CH₃)₂NH > CH₃NH₂ > NH₃
c) NH₃ > CH₃NH₂ > (CH₃)₂NH > (CH₃)₃N
d) (CH₃)₂NH > CH₃NH₂ > (CH₃)₃N > NH₃

JEE Advanced 2021 Paper 2

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Answer: d) (CH₃)₂NH > CH₃NH₂ > (CH₃)₃N > NH₃

Explanation: In gas phase: +I effect of alkyl groups increases basicity.
Order: 2° > 1° > 3° > NH₃
• (CH₃)₂NH: two +I groups + H-bonding in solution
• (CH₃)₃N: steric hindrance + solvation ↓ in water

4. [JEE Main 2024] The strongest acid among the following is:

a) CH₃CH₂COOH
b) CH₃CH₂CH₂COOH
c) (CH₃)₂CHCOOH
d) (CH₃)₃CCOOH

JEE Main 2024 | 6 April Shift 1

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Answer: a) CH₃CH₂COOH

Explanation: Alkyl groups are +I → destabilize COO⁻ → decrease acidity.
• CH₃CH₂–: closest to COOH → least +I effect
• (CH₃)₃C–: farthest + strongest +I → weakest acid

5. [NEET 2023] The correct order of –I effect is:

a) –F > –Cl > –Br > –I
b) –I > –Br > –Cl > –F
c) –F > –Cl > –I > –Br
d) –Cl > –Br > –F > –I

NEET 2023

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Answer: a) –F > –Cl > –Br > –I

Explanation: –I effect ∝ electronegativity.
F (4.0) > Cl (3.0) > Br (2.8) > I (2.5)

6. [JEE Adv 2020] The compound with highest dipole moment is:

a) CH₃–F
b) CH₃–Cl
c) CH₃–Br
d) CH₃–I

JEE Advanced 2020 Paper 1

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Answer: a) CH₃–F

Explanation: Dipole moment = EN difference × bond length.
• C–F: highest EN diff (1.5) + shortest bond
• C–I: lowest EN diff + longest bond → lowest μ

7. [JEE Main 2022] The weakest base is:

a) NH₃
b) CH₃NH₂
c) (CH₃)₂NH
d) C₆H₅NH₂

JEE Main 2022 | 29 June Shift 2

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Answer: d) C₆H₅NH₂

Explanation: In aniline, lone pair delocalized into ring → less available.
• Alkylamines: +I effect → stronger base than NH₃
• Aniline: resonance + –I from sp² carbon → weakest

8. [NEET 2021] Inductive effect is a:

a) Permanent effect
b) Temporary effect
c) Through-bond effect
d) Both a and c

NEET 2021

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Answer: d) Both a and c

Explanation: • Permanent (always present)
• Operates through σ bonds
• Distance-dependent: α > β > γ

9. [JEE Adv 2019] The order of reactivity towards SN1 is:

a) CH₃CH₂Cl > (CH₃)₂CHCl > (CH₃)₃CCl
b) (CH₃)₃CCl > (CH₃)₂CHCl > CH₃CH₂Cl
c) CH₃CH₂Cl > (CH₃)₃CCl > (CH₃)₂CHCl
d) All equal

JEE Advanced 2019 Paper 2

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Answer: b) (CH₃)₃CCl > (CH₃)₂CHCl > CH₃CH₂Cl

Explanation: SN1 ∝ carbocation stability.
• (CH₃)₃C⁺: 3° + 9 α-H (+I strongest)
• (CH₃)₂CH⁺: 2° + 6 α-H
• CH₃CH₂⁺: 1° + 3 α-H

10. [JEE Main 2025] The pKa of CH₃CH₂CH₂COOH is closest to:

a) 4.2
b) 4.8
c) 5.0
d) 5.5

JEE Main 2025 | Predicted

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Answer: b) 4.8

Explanation: Butanoic acid: CH₃CH₂CH₂COOH
• +I effect from propyl group (weaker than ethyl)
• pKa ≈ 4.8 (standard value)

11. [JEE Adv 2022] The group with strongest +I effect is:

a) –CH₃
b) –CH₂CH₃
c) –CH(CH₃)₂
d) –C(CH₃)₃

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Answer: d) –C(CH₃)₃

Explanation: +I ∝ number of alkyl groups attached to carbon.
tert-Butyl > iso-Propyl > Ethyl > Methyl

12. [NEET 2020] Acidity of nitroalkanes follows order:

a) 1° > 2° > 3°
b) 3° > 2° > 1°
c) 2° > 1° > 3°
d) All equal

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Answer: a) 1° > 2° > 3°

Explanation: –NO₂ is strong –I group. In R–CH₂–NO₂:
• 1°: least +I from R → most acidic
• 3°: maximum +I → least acidic

13. [JEE Main 2021] The correct order of bond length is:

a) C–F < C–Cl < C–Br < C–I
b) C–I < C–Br < C–Cl < C–F
c) C–Cl < C–F < C–Br < C–I
d) C–F = C–Cl = C–Br = C–I

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Answer: a) C–F < C–Cl < C–Br < C–I

Explanation: Bond length ∝ atomic size.
F < Cl < Br < I → C–F shortest, C–I longest

14. [JEE Adv 2018] The strongest acid is:

a) CH₃COOH
b) ClCH₂COOH
c) BrCH₂COOH
d) ICH₂COOH

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Answer: b) ClCH₂COOH

Explanation: –I order: F > Cl > Br > I
But ClCH₂COOH > BrCH₂COOH due to stronger –I of Cl and shorter distance.

15. [NEET 2019] The inductive effect is maximum in:

a) –CH₃
b) –F
c) –OH
d) –NH₂

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Answer: b) –F

Explanation: Highest electronegativity → strongest –I effect.

16. [JEE Main 2020] The order of basicity in gas phase is:

a) NH₃ < CH₃NH₂ < (CH₃)₂NH < (CH₃)₃N
b) (CH₃)₃N < (CH₃)₂NH < CH₃NH₂ < NH₃
c) (CH₃)₃N > (CH₃)₂NH > CH₃NH₂ > NH₃
d) All equal

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Answer: c) (CH₃)₃N > (CH₃)₂NH > CH₃NH₂ > NH₃

Explanation: In gas phase: no solvation → pure +I effect dominates → 3° > 2° > 1° > NH₃

17. [JEE Adv 2023] The compound with lowest pKa is:

a) CH₃CH₂OH
b) CF₃CH₂OH
c) CH₃OH
d) CCl₃CH₂OH

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Answer: b) CF₃CH₂OH

Explanation: –CF₃ is strongest –I group → stabilizes alkoxide → lowest pKa.

18. [NEET 2024] The inductive effect operates through:

a) π bonds
b) σ bonds
c) Lone pairs
d) d-orbitals

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Answer: b) σ bonds

Explanation: Polarization transmitted through sigma framework.

19. [JEE Main 2019] The correct order of +I effect is:

a) –H > –CH₃ > –C₂H₅ > –C₃H₇
b) –C(CH₃)₃ > –CH(CH₃)₂ > –C₂H₅ > –CH₃
c) –CH₃ > –C₂H₅ > –CH(CH₃)₂ > –C(CH₃)₃
d) All equal

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Answer: b) –C(CH₃)₃ > –CH(CH₃)₂ > –C₂H₅ > –CH₃

Explanation: More alkyl groups → stronger electron donation → stronger +I.

20. [JEE Adv 2024] The pKa order of the following is:

a) FCH₂COOH > ClCH₂COOH > BrCH₂COOH > ICH₂COOH
b) FCH₂COOH < ClCH₂COOH < BrCH₂COOH < ICH₂COOH
c) ICH₂COOH < BrCH₂COOH < ClCH₂COOH < FCH₂COOH
d) All equal

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Answer: c) ICH₂COOH < BrCH₂COOH < ClCH₂COOH < FCH₂COOH

Explanation: Acidity ∝ –I strength.
F > Cl > Br > I → FCH₂COOH strongest acid (lowest pKa)