NEET Organic Compounds Containing Nitrogen & Carboxylic Acids PYQs with Solutions

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Verified Against NTA Final Answer Key

Option (1) : Both Statement-I and Statement-II are correct.

📚 Organic Compounds Containing Nitrogen & Carboxylic Acids Medium

📋 Given Parameters & Problem Setup

Statement-I Oxidation of p-nitrotoluene with acidic KMnO₄ gives an acid that is stronger than benzoic acid.

Statement-II Reduction of p-nitrotoluene with Sn/HCl followed by neutralization gives an amine that is more basic than aniline.

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The 30-Second Exam Hall Shortcut: ⚡ Acid/Base Substituent Effects

⏱️ Save ~60 seconds

-NO₂ withdraws electrons (increases acidity); -CH₃ donates electrons (increases basicity)!

1 Statement-I: Oxidation of p-nitrotoluene oxidizes -CH₃ to -COOH, forming p-nitrobenzoic acid. The strong electron-withdrawing nitro group (-I, -M) disperses the carboxylate negative charge, making it STRONGER than benzoic acid (pKa 3.44 vs 4.20) -> TRUE!

2 Statement-II: Reduction with Sn/HCl selectively reduces -NO₂ to -NH₂, leaving -CH₃ intact to give p-toluidine (p-methylaniline). The electron-releasing methyl group (+I and hyperconjugation) increases electron density on the -NH₂ lone pair, making it MORE BASIC than aniline (pKb 8.92 vs 9.38) -> TRUE!

3 Both statements are scientifically correct -> Option (1) in 15 seconds!

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Why You Can 100% Trust This Shortcut: Canonical organic principles: Electron-withdrawing groups stabilize carboxylate anions (increase acidity); Electron-donating groups increase lone pair availability on nitrogen (increase basicity).

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Step-by-Step Rigorous Workflow & Mathematical Proof

Step 1

Analyze Statement-I (Oxidation to p-Nitrobenzoic Acid)

Vigorous oxidation of an alkylbenzene derivative with acidic potassium permanganate (KMnO₄/H⁺) oxidizes the benzylic methyl group to a carboxylic acid group (-COOH), while the nitro group remains inert.

p\text{-NO}_2-\text{C}_6\text{H}_4-\text{CH}_3 \xrightarrow{\text{KMnO}_4, \text{H}^+} p\text{-NO}_2-\text{C}_6\text{H}_4-\text{COOH} \quad (p\text{-nitrobenzoic acid})

• The nitro group (-NO₂) is a powerful electron-withdrawing group via inductive (-I) and mesomeric (-M) effects.
• By delocalizing and dispersing the negative charge on the conjugate base (p-nitrobenzoate anion), it strongly stabilizes the conjugate base.
• Therefore, p-nitrobenzoic acid (pKa = 3.44) is a much stronger acid than unsubstituted benzoic acid (pKa = 4.20).
• Statement-I is correct.

Step 2

Analyze Statement-II (Reduction to p-Toluidine)

Reduction of p-nitrotoluene using tin and concentrated hydrochloric acid (Sn/HCl) followed by basic neutralization selectively reduces the aromatic nitro group (-NO₂) to an amino group (-NH₂), leaving the methyl group unaffected.

p\text{-NO}_2-\text{C}_6\text{H}_4-\text{CH}_3 \xrightarrow{\text{1. Sn/HCl, 2. NaOH}} p\text{-CH}_3-\text{C}_6\text{H}_4-\text{NH}_2 \quad (p\text{-toluidine})

• The methyl group (-CH₃) is an electron-donating group via positive inductive (+I) and hyperconjugation effects.
• Electron donation increases the electron density on the nitrogen atom, enhancing the availability of its lone pair for protonation.
• Therefore, p-toluidine (pKb = 8.92) is more basic than unsubstituted aniline (pKb = 9.38).
• Statement-II is correct.

Step 3

Formulate Conclusion

Both Statement-I and Statement-II are correct.

\text{Statement-I: True}, \quad \text{Statement-II: True} \implies \text{Both are correct (Option 1)}

• Matches Option (1).

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360° Option Elimination Engine Key Feature

Diagnose every choice: Know exactly why the right option works and why distractors fail.

4-Option Deep Scan

1 A

✓ 100% Correct

Verdict & Scientific Reason:

Scientifically flawless: -NO₂ strengthens the benzoic acid, and -CH₃ strengthens the basicity of the toluidine.

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Why this is airtight: None; perfect understanding of substituent electronic effects.

2 B

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. Both statements represent standard textbook chemistry.

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Student Fallacy (Why candidates pick this trap): Doubting both standard functional group reactions.

3 C

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. Falsely assumes p-toluidine is less basic than aniline.

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Student Fallacy (Why candidates pick this trap): Confusing basicity in aromatic amines with steric hindrance of ortho substituents.

4 D

✗ Incorrect

Verdict & Scientific Reason:

Incorrect. Falsely claims p-nitrobenzoic acid is weaker than benzoic acid.

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Student Fallacy (Why candidates pick this trap): Inverting the effect of electron-withdrawing groups on acid strength.

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NTA Trap Alert: Confusing the Ortho Effect with Para Substituents

In ortho-substituted benzoic acids and anilines, the ortho-effect can alter expected acidity/basicity. But here, the substituents are strictly PARA (p-nitrotoluene), where electronic effects (+I/+M and -I/-M) govern smoothly without steric inhibition of resonance.

🛡️ How to avoid the -1 mark: Para -NO₂ increases acidity; Para -CH₃ increases basicity. Both statements are TRUE.

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Core NEET Syllabus Standard

NEET Chemistry Core Syllabus · Carboxylic Acids & Amines Standard Benchmark

Core Scientific Principle Tested:

"Electron-withdrawing groups enhance carboxylic acidity; electron-donating groups enhance amine basicity."

Syllabus Focus: Acidity of substituted benzoic acids and basicity of substituted anilines

✓ Core NEET UG Syllabus Anchor Syllabus & Academic Standards ↗

NO₂ pulls electrons to make acid strong; CH₃ pushes electrons to make base belong!

NEET Organic Compounds Containing Nitrogen & Carboxylic Acids Previous Year Questions with Solutions

The 30-Second Exam Hall Shortcut: ⚡ Acid/Base Substituent Effects

Step-by-Step Rigorous Workflow & Mathematical Proof

Analyze Statement-I (Oxidation to p-Nitrobenzoic Acid)

Analyze Statement-II (Reduction to p-Toluidine)

Formulate Conclusion

360° Option Elimination Engine Key Feature

NTA Trap Alert: Confusing the Ortho Effect with Para Substituents

Core NEET Syllabus Standard

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