ACS Organic Chemistry II Examination
Questions and Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
1. Benzene undergoes electrophilic aromatic substitution primarily because it:
A. Is highly reactive toward nucleophiles
B. Contains localized π bonds
C. Readily breaks its aromatic ring
D. Preserves aromatic stability during substitution
Correct Answer: D. Preserves aromatic stability during substitution
Rationale: Electrophilic aromatic substitution replaces a hydrogen while restoring
aromaticity, making substitution far more favorable than addition.
2. The electrophile in nitration of benzene is:
A. NO₂⁻
B. HNO₃
C. NO
D. NO₂⁺
Correct Answer: D. NO₂⁺
Rationale: Sulfuric acid protonates nitric acid to generate the nitronium ion (NO₂⁺),
the active electrophile.
3. Concentrated sulfuric acid is used in aromatic nitration because it:
,A. Reduces benzene
B. Oxidizes benzene
C. Removes nitro groups
D. Generates the nitronium ion
Correct Answer: D. Generates the nitronium ion
Rationale: Sulfuric acid acts as a stronger acid, producing NO₂⁺ from nitric acid.
4. Which substituent activates a benzene ring toward electrophilic substitution?
A. Nitro (–NO₂)
B. Carbonyl (–CHO)
C. Cyano (–CN)
D. Hydroxyl (–OH)
Correct Answer: D. Hydroxyl (–OH)
Rationale: The hydroxyl group donates electron density through resonance,
activating the ring.
5. Which substituent strongly deactivates an aromatic ring?
A. Methoxy (–OCH₃)
B. Methyl (–CH₃)
C. Amino (–NH₂)
D. Nitro (–NO₂)
Correct Answer: D. Nitro (–NO₂)
Rationale: The nitro group withdraws electron density by resonance and induction.
6. Most activating groups direct incoming electrophiles to the:
A. Meta positions only
B. Random positions
,C. Para position only
D. Ortho and para positions
Correct Answer: D. Ortho and para positions
Rationale: Electron-donating groups stabilize the ortho and para sigma
complexes.
7. Nitro groups direct substitution primarily to the:
A. Ortho position
B. Para position
C. All positions equally
D. Meta position
Correct Answer: D. Meta position
Rationale: Electron-withdrawing groups destabilize ortho and para intermediates,
favoring meta substitution.
8. Friedel–Crafts alkylation requires which catalyst?
A. H₂SO₄
B. NaOH
C. Pd/C
D. AlCl₃
Correct Answer: D. AlCl₃
Rationale: Aluminum chloride is a Lewis acid that generates the electrophile from
an alkyl halide.
9. Friedel–Crafts acylation introduces a(n):
A. Alkene group
B. Alcohol group
, C. Amine group
D. Acyl group
Correct Answer: D. Acyl group
Rationale: Acylation installs a carbonyl-containing acyl substituent onto the
aromatic ring.
10. Phenol is more acidic than cyclohexanol because:
A. It is heavier
B. It contains more hydrogen atoms
C. It is more polar
D. Its conjugate base is resonance stabilized
Correct Answer: D. Its conjugate base is resonance stabilized
Rationale: The phenoxide ion is stabilized by resonance over the aromatic ring.
11. Which reagent commonly oxidizes a primary alcohol to a carboxylic acid?
A. H₂/Pd
B. NaBH₄
C. LiAlH₄
D. KMnO₄
Correct Answer: D. KMnO₄
Rationale: Potassium permanganate is a strong oxidizing agent that converts
primary alcohols to carboxylic acids.
12. Sodium borohydride (NaBH₄) reduces aldehydes to:
A. Alkanes
B. Ketones
C. Carboxylic acids
D. Primary alcohols
Questions and Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
1. Benzene undergoes electrophilic aromatic substitution primarily because it:
A. Is highly reactive toward nucleophiles
B. Contains localized π bonds
C. Readily breaks its aromatic ring
D. Preserves aromatic stability during substitution
Correct Answer: D. Preserves aromatic stability during substitution
Rationale: Electrophilic aromatic substitution replaces a hydrogen while restoring
aromaticity, making substitution far more favorable than addition.
2. The electrophile in nitration of benzene is:
A. NO₂⁻
B. HNO₃
C. NO
D. NO₂⁺
Correct Answer: D. NO₂⁺
Rationale: Sulfuric acid protonates nitric acid to generate the nitronium ion (NO₂⁺),
the active electrophile.
3. Concentrated sulfuric acid is used in aromatic nitration because it:
,A. Reduces benzene
B. Oxidizes benzene
C. Removes nitro groups
D. Generates the nitronium ion
Correct Answer: D. Generates the nitronium ion
Rationale: Sulfuric acid acts as a stronger acid, producing NO₂⁺ from nitric acid.
4. Which substituent activates a benzene ring toward electrophilic substitution?
A. Nitro (–NO₂)
B. Carbonyl (–CHO)
C. Cyano (–CN)
D. Hydroxyl (–OH)
Correct Answer: D. Hydroxyl (–OH)
Rationale: The hydroxyl group donates electron density through resonance,
activating the ring.
5. Which substituent strongly deactivates an aromatic ring?
A. Methoxy (–OCH₃)
B. Methyl (–CH₃)
C. Amino (–NH₂)
D. Nitro (–NO₂)
Correct Answer: D. Nitro (–NO₂)
Rationale: The nitro group withdraws electron density by resonance and induction.
6. Most activating groups direct incoming electrophiles to the:
A. Meta positions only
B. Random positions
,C. Para position only
D. Ortho and para positions
Correct Answer: D. Ortho and para positions
Rationale: Electron-donating groups stabilize the ortho and para sigma
complexes.
7. Nitro groups direct substitution primarily to the:
A. Ortho position
B. Para position
C. All positions equally
D. Meta position
Correct Answer: D. Meta position
Rationale: Electron-withdrawing groups destabilize ortho and para intermediates,
favoring meta substitution.
8. Friedel–Crafts alkylation requires which catalyst?
A. H₂SO₄
B. NaOH
C. Pd/C
D. AlCl₃
Correct Answer: D. AlCl₃
Rationale: Aluminum chloride is a Lewis acid that generates the electrophile from
an alkyl halide.
9. Friedel–Crafts acylation introduces a(n):
A. Alkene group
B. Alcohol group
, C. Amine group
D. Acyl group
Correct Answer: D. Acyl group
Rationale: Acylation installs a carbonyl-containing acyl substituent onto the
aromatic ring.
10. Phenol is more acidic than cyclohexanol because:
A. It is heavier
B. It contains more hydrogen atoms
C. It is more polar
D. Its conjugate base is resonance stabilized
Correct Answer: D. Its conjugate base is resonance stabilized
Rationale: The phenoxide ion is stabilized by resonance over the aromatic ring.
11. Which reagent commonly oxidizes a primary alcohol to a carboxylic acid?
A. H₂/Pd
B. NaBH₄
C. LiAlH₄
D. KMnO₄
Correct Answer: D. KMnO₄
Rationale: Potassium permanganate is a strong oxidizing agent that converts
primary alcohols to carboxylic acids.
12. Sodium borohydride (NaBH₄) reduces aldehydes to:
A. Alkanes
B. Ketones
C. Carboxylic acids
D. Primary alcohols
