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Organic Chemistry - Janice Gorzynski Smith |
Carbonyl Chemistry, Aromatic Reactions &
Synthesis Practice Exam
200 advanced reaction, carbonyl, aromatic, enolate, amine, and synthesis
questions
QUESTIONS FORMAT COVERAGE
200 A-D + Explanations Advanced Topics
Original practice questions for independent study and exam preparation.
,Carbonyl Chemistry, Aromatic Reactions & Synthesis Practice Exam
Practice Questions
Choose the best answer for each item. The answer and a detailed explanation follow each question.
Aromatic chemistry
1. Which statement best describes a methoxy substituent on benzene during electrophilic aromatic substitution?
A. it directs meta because oxygen withdraws by resonance
B. it is non-directing
C. it strongly activates the ring and directs ortho/para
D. it strongly deactivates and directs meta
Answer: C
Explanation: Methoxy donates a lone pair into the aromatic ring by resonance. This increases ring electron density and stabilizes ortho
and para sigma complexes. The substituent is therefore strongly activating and ortho/para directing.
Aromatic chemistry
2. Which statement best describes a nitro substituent on benzene during electrophilic aromatic substitution?
A. it strongly activates and directs ortho/para
B. it strongly deactivates the ring and directs meta
C. it activates but directs meta
D. it is neutral and non-directing
Answer: B
Explanation: Nitro withdraws electron density by both resonance and induction. Ortho and para attack generates especially
unfavorable resonance contributors with positive charge near the nitro group. Meta substitution avoids those worst contributors, so nitro
is a strong meta director.
Aromatic chemistry
3. Which statement best describes a halogen substituent on benzene in electrophilic aromatic substitution?
A. it is completely non-directing
B. it activates strongly and directs meta
C. it deactivates the ring but directs ortho/para
D. it activates the ring by induction
Answer: C
Explanation: Halogens withdraw inductively and therefore deactivate the ring overall. Their lone pairs can donate by resonance and
stabilize ortho/para sigma complexes. This produces the unusual combination of deactivation with ortho/para direction.
Aromatic chemistry
4. Which statement best describes an alkyl group on benzene?
A. it activates the ring and directs ortho/para
B. it converts the ring into an alkyne
C. it is non-directing
D. it strongly deactivates and directs meta
Answer: A
Explanation: Alkyl groups donate electron density by hyperconjugation and inductive effects. They stabilize cationic sigma complexes
formed at ortho and para positions. Alkylbenzenes are therefore generally more reactive than benzene toward electrophilic substitution.
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,Carbonyl Chemistry, Aromatic Reactions & Synthesis Practice Exam
Aromatic chemistry
5. Which statement best describes a carbonyl-containing substituent such as -CHO directly attached to benzene?
A. it is always neutral
B. it strongly activates and directs ortho/para
C. it behaves like an alkyl group
D. it generally deactivates the ring and directs meta
Answer: D
Explanation: A directly attached carbonyl withdraws electron density from the aromatic ring by resonance and induction. Ortho and
para sigma complexes place positive charge in especially unfavorable relation to the electron-withdrawing group. Meta substitution is
therefore favored.
Aromatic chemistry
6. Which statement best describes nitration of benzene?
A. NaBH4 generates NO2+
B. HNO3 and H2SO4 generate the nitronium electrophile NO2+
C. Br2 alone generates NO2+
D. H2/Pd generates NO2+
Answer: B
Explanation: Concentrated sulfuric acid protonates nitric acid and promotes formation of the nitronium ion. NO2+ is the electrophile that
attacks the aromatic pi system. Deprotonation then restores aromaticity and yields nitrobenzene.
Aromatic chemistry
7. Which statement best describes bromination of benzene?
A. H2/Pd is required
B. NaBH4 is required
C. Br2 with FeBr3 provides an activated brominating electrophile
D. Br2 with peroxides gives the standard EAS pathway
Answer: C
Explanation: Benzene is not nucleophilic enough to react rapidly with Br2 alone under ordinary conditions. FeBr3 coordinates to
bromine and creates a more powerful electrophile. Aromatic attack followed by deprotonation yields bromobenzene.
Aromatic chemistry
8. Which statement best describes Friedel-Crafts alkylation?
A. a Lewis acid such as AlCl3 activates an alkyl halide electrophile
B. strongly deactivated rings react fastest
C. the reaction cannot form C-C bonds
D. the reaction uses NaBH4 as the electrophile generator
Answer: A
Explanation: Friedel-Crafts alkylation uses a Lewis acid to generate or approximate a carbocation electrophile from an alkyl halide. The
aromatic ring attacks that electrophile to form a new carbon-carbon bond. Strongly deactivated aromatic rings generally react poorly.
Aromatic chemistry
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, Carbonyl Chemistry, Aromatic Reactions & Synthesis Practice Exam
9. Which statement best describes a major limitation of Friedel-Crafts alkylation?
A. it never forms carbon-carbon bonds
B. it only works on nitrobenzene
C. the alkyl group strongly deactivates the product
D. carbocation rearrangements and polyalkylation can occur
Answer: D
Explanation: Carbocation-like electrophiles can rearrange before aromatic attack, changing the carbon skeleton. The first alkyl group
also activates the ring, making further alkylation easier. These features can complicate control of product structure and stoichiometry.
Aromatic chemistry
10. Which statement best describes Friedel-Crafts acylation?
A. the acylium ion is resonance-stabilized and does not undergo ordinary alkyl-type rearrangement
B. the electrophile is a free methyl radical
C. the product contains no carbonyl
D. polyacylation is usually accelerated by the first acyl group
Answer: A
Explanation: Acid chlorides or anhydrides with AlCl3 generate an acylium electrophile. The acylium ion is resonance-stabilized and
does not rearrange like a simple carbocation. The acyl group also deactivates the product ring, which helps limit repeated acylation.
Aromatic chemistry
11. Which statement best describes sulfonation of benzene?
A. the reaction is irreversible under all conditions
B. the reaction is reversible and can be used as a temporary blocking strategy
C. it requires a Grignard reagent
D. it reduces benzene to cyclohexane
Answer: B
Explanation: Aromatic sulfonation introduces an SO3H group under strongly acidic conditions. Heating with dilute acid can reverse the
process and remove the sulfonyl group. This reversibility makes sulfonation useful as a temporary directing or blocking operation.
Aromatic chemistry
12. Which statement best describes benzylic oxidation of an alkylbenzene with hot KMnO4?
A. a benzylic hydrogen prevents oxidation
B. a side chain containing at least one benzylic hydrogen can be oxidized to a carboxylic acid
C. the aromatic ring is always destroyed first
D. the side chain is reduced to methane
Answer: B
Explanation: Strong permanganate oxidizes benzylic carbon atoms bearing at least one hydrogen. Regardless of side-chain length, the
carbon attached to the ring is converted to a carboxyl group under vigorous conditions. A side chain with no benzylic hydrogen resists
this common transformation.
Organometallic chemistry
13. Which statement best describes CH3MgBr reacting with formaldehyde followed by acidic workup?
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Organic Chemistry - Janice Gorzynski Smith |
Carbonyl Chemistry, Aromatic Reactions &
Synthesis Practice Exam
200 advanced reaction, carbonyl, aromatic, enolate, amine, and synthesis
questions
QUESTIONS FORMAT COVERAGE
200 A-D + Explanations Advanced Topics
Original practice questions for independent study and exam preparation.
,Carbonyl Chemistry, Aromatic Reactions & Synthesis Practice Exam
Practice Questions
Choose the best answer for each item. The answer and a detailed explanation follow each question.
Aromatic chemistry
1. Which statement best describes a methoxy substituent on benzene during electrophilic aromatic substitution?
A. it directs meta because oxygen withdraws by resonance
B. it is non-directing
C. it strongly activates the ring and directs ortho/para
D. it strongly deactivates and directs meta
Answer: C
Explanation: Methoxy donates a lone pair into the aromatic ring by resonance. This increases ring electron density and stabilizes ortho
and para sigma complexes. The substituent is therefore strongly activating and ortho/para directing.
Aromatic chemistry
2. Which statement best describes a nitro substituent on benzene during electrophilic aromatic substitution?
A. it strongly activates and directs ortho/para
B. it strongly deactivates the ring and directs meta
C. it activates but directs meta
D. it is neutral and non-directing
Answer: B
Explanation: Nitro withdraws electron density by both resonance and induction. Ortho and para attack generates especially
unfavorable resonance contributors with positive charge near the nitro group. Meta substitution avoids those worst contributors, so nitro
is a strong meta director.
Aromatic chemistry
3. Which statement best describes a halogen substituent on benzene in electrophilic aromatic substitution?
A. it is completely non-directing
B. it activates strongly and directs meta
C. it deactivates the ring but directs ortho/para
D. it activates the ring by induction
Answer: C
Explanation: Halogens withdraw inductively and therefore deactivate the ring overall. Their lone pairs can donate by resonance and
stabilize ortho/para sigma complexes. This produces the unusual combination of deactivation with ortho/para direction.
Aromatic chemistry
4. Which statement best describes an alkyl group on benzene?
A. it activates the ring and directs ortho/para
B. it converts the ring into an alkyne
C. it is non-directing
D. it strongly deactivates and directs meta
Answer: A
Explanation: Alkyl groups donate electron density by hyperconjugation and inductive effects. They stabilize cationic sigma complexes
formed at ortho and para positions. Alkylbenzenes are therefore generally more reactive than benzene toward electrophilic substitution.
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,Carbonyl Chemistry, Aromatic Reactions & Synthesis Practice Exam
Aromatic chemistry
5. Which statement best describes a carbonyl-containing substituent such as -CHO directly attached to benzene?
A. it is always neutral
B. it strongly activates and directs ortho/para
C. it behaves like an alkyl group
D. it generally deactivates the ring and directs meta
Answer: D
Explanation: A directly attached carbonyl withdraws electron density from the aromatic ring by resonance and induction. Ortho and
para sigma complexes place positive charge in especially unfavorable relation to the electron-withdrawing group. Meta substitution is
therefore favored.
Aromatic chemistry
6. Which statement best describes nitration of benzene?
A. NaBH4 generates NO2+
B. HNO3 and H2SO4 generate the nitronium electrophile NO2+
C. Br2 alone generates NO2+
D. H2/Pd generates NO2+
Answer: B
Explanation: Concentrated sulfuric acid protonates nitric acid and promotes formation of the nitronium ion. NO2+ is the electrophile that
attacks the aromatic pi system. Deprotonation then restores aromaticity and yields nitrobenzene.
Aromatic chemistry
7. Which statement best describes bromination of benzene?
A. H2/Pd is required
B. NaBH4 is required
C. Br2 with FeBr3 provides an activated brominating electrophile
D. Br2 with peroxides gives the standard EAS pathway
Answer: C
Explanation: Benzene is not nucleophilic enough to react rapidly with Br2 alone under ordinary conditions. FeBr3 coordinates to
bromine and creates a more powerful electrophile. Aromatic attack followed by deprotonation yields bromobenzene.
Aromatic chemistry
8. Which statement best describes Friedel-Crafts alkylation?
A. a Lewis acid such as AlCl3 activates an alkyl halide electrophile
B. strongly deactivated rings react fastest
C. the reaction cannot form C-C bonds
D. the reaction uses NaBH4 as the electrophile generator
Answer: A
Explanation: Friedel-Crafts alkylation uses a Lewis acid to generate or approximate a carbocation electrophile from an alkyl halide. The
aromatic ring attacks that electrophile to form a new carbon-carbon bond. Strongly deactivated aromatic rings generally react poorly.
Aromatic chemistry
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, Carbonyl Chemistry, Aromatic Reactions & Synthesis Practice Exam
9. Which statement best describes a major limitation of Friedel-Crafts alkylation?
A. it never forms carbon-carbon bonds
B. it only works on nitrobenzene
C. the alkyl group strongly deactivates the product
D. carbocation rearrangements and polyalkylation can occur
Answer: D
Explanation: Carbocation-like electrophiles can rearrange before aromatic attack, changing the carbon skeleton. The first alkyl group
also activates the ring, making further alkylation easier. These features can complicate control of product structure and stoichiometry.
Aromatic chemistry
10. Which statement best describes Friedel-Crafts acylation?
A. the acylium ion is resonance-stabilized and does not undergo ordinary alkyl-type rearrangement
B. the electrophile is a free methyl radical
C. the product contains no carbonyl
D. polyacylation is usually accelerated by the first acyl group
Answer: A
Explanation: Acid chlorides or anhydrides with AlCl3 generate an acylium electrophile. The acylium ion is resonance-stabilized and
does not rearrange like a simple carbocation. The acyl group also deactivates the product ring, which helps limit repeated acylation.
Aromatic chemistry
11. Which statement best describes sulfonation of benzene?
A. the reaction is irreversible under all conditions
B. the reaction is reversible and can be used as a temporary blocking strategy
C. it requires a Grignard reagent
D. it reduces benzene to cyclohexane
Answer: B
Explanation: Aromatic sulfonation introduces an SO3H group under strongly acidic conditions. Heating with dilute acid can reverse the
process and remove the sulfonyl group. This reversibility makes sulfonation useful as a temporary directing or blocking operation.
Aromatic chemistry
12. Which statement best describes benzylic oxidation of an alkylbenzene with hot KMnO4?
A. a benzylic hydrogen prevents oxidation
B. a side chain containing at least one benzylic hydrogen can be oxidized to a carboxylic acid
C. the aromatic ring is always destroyed first
D. the side chain is reduced to methane
Answer: B
Explanation: Strong permanganate oxidizes benzylic carbon atoms bearing at least one hydrogen. Regardless of side-chain length, the
carbon attached to the ring is converted to a carboxyl group under vigorous conditions. A side chain with no benzylic hydrogen resists
this common transformation.
Organometallic chemistry
13. Which statement best describes CH3MgBr reacting with formaldehyde followed by acidic workup?
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