Daily Practice Problems (DPP)
Mesomeric Effect (Resonance Effect)
Q1. The stability of 2,3-dimethyl but-2-ene is more than 2-butene. This can be explained in terms of:
- (a) Resonance
- (b) Hyperconjugation
- (c) Electromeric effect
- (d) Inductive effect
(NEET Practice PYQ)
Q2. In which of the following molecules all the effects namely inductive, mesomeric and hyperconjugation operate?
- (a) CH₃-CH₂-CH₃
- (b) CH₃-CH=CH₂
- (c) CH₃-CH₂-Cl
- (d) CH₃-CH₂-OH
(NEET PYQ)
Q3. The +I (inductive effect) is shown by:
- (a) -CH₃
- (b) -OH
- (c) -F
- (d) -C₆H₅
(NEET PYQ)
Q4. Methyl group attached to a positively charged carbon atom stabilizes the carbocation due to:
- (a) -I inductive effect
- (b) Electromeric effect
- (c) Hyperconjugation
- (d) Mesomeric effect
(NEET PYQ)
Q5. Due to +M effect of –OH group and hyperconjugation of –CH₃ group, the correct order of stability is:
- (a) A > B > C
- (b) B > A > C
- (c) C > A > B
- (d) A > C > B
(NEET PYQ, 31-Year Compilation)
Q6. How many compounds among the following show inductive, mesomeric as well as hyperconjugation effects? (Structures: Assume standard benzene derivatives with substituents like -OH, -CH₃, -NO₂)
- (a) 1
- (b) 2
- (c) 3
- (d) 4
(JEE Main 2021 (Online) 26th February Morning Shift)
Q7. Given below are two statements:
Statement I: Hyperconjugation is a permanent effect.
Statement II: Mesomeric effect involves delocalization of π-electrons.
In the light of the above statements, choose the most appropriate answer from the options given below:
- (a) Both Statement I and Statement II are correct
- (b) Both Statement I and Statement II are incorrect
- (c) Statement I is correct but Statement II is incorrect
- (d) Statement I is incorrect but Statement II is correct
(JEE Main PYQ)
Q8. The acidity of phenols is due to:
- (a) Inductive effect
- (b) Hyperconjugation
- (c) Mesomeric effect
- (d) Electromeric effect
(JEE Main PYQ)
Q9. In nitrobenzene, the nitro group shows:
- (a) +M effect
- (b) -M effect
- (c) +I effect
- (d) -I effect
(JEE Main PYQ)
Q10. The order of +M effect is:
- (a) –NH₂ > –OH > –OR
- (b) –OH > –NH₂ > –OR
- (c) –OR > –OH > –NH₂
- (d) –NH₂ > –OR > –OH
(NEET/JEE Practice PYQ)
Answer Key with Detailed Solutions
Q1. Answer: (b) Hyperconjugation
Explanation: Stability due to more alpha hydrogens for hyperconjugation, not mesomeric (no conjugation).
Year: NEET Practice (Similar to 2018)
Q2. Answer: (d) CH₃-CH₂-OH
Explanation: -OH shows +M (mesomeric), -CH₂- shows +I (inductive), and CH₃ shows hyperconjugation.
Year: NEET 2020
Q3. Answer: (a) -CH₃
Explanation: Alkyl groups show +I; -OH, -F show -I; phenyl shows mixed.
Year: NEET 2019
Q4. Answer: (c) Hyperconjugation
Explanation: No π-system for mesomeric; hyperconjugation from C-H sigma bonds.
Year: NEET 2021
Q5. Answer: (b) B > A > C
Explanation: +M of -OH and hyperconjugation of -CH₃ stabilize intermediates.
Year: NEET 31-Year Compilation (2017)
Q6. Answer: (c) 3
Explanation: Compounds with alkyl + conjugating groups (e.g., phenol, anisole).
Year: JEE Main 2021
Q7. Answer: (d) Statement I is incorrect but Statement II is correct
Explanation: Hyperconjugation is permanent but delocalizes sigma electrons; mesomeric is π-delocalization.
Year: JEE Main 2022
Q8. Answer: (c) Mesomeric effect
Explanation: Resonance stabilization of phenoxide ion via +M delocalization.
Year: JEE Main 2019
Q9. Answer: (b) -M effect
Explanation: -NO₂ withdraws electrons through resonance, deactivating ring.
Year: JEE Main 2020
Q10. Answer: (a) –NH₂ > –OH > –OR
Explanation: Lone pair donation strength: N > O (alkyl substitution reduces in -OR).
Year: NEET 2018
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