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CHEM 210 Exam 5 | Advanced Organic Chemistry | In-
Depth Conceptual & Application-Based Questions | Graded
A+
[1] Which of the following statements best describes the relationship between the rate of an
SN2 reaction and the structure of the alkyl halide?
A. The rate increases as the steric hindrance around the electrophilic carbon increases.
B. The rate is independent of the structure of the alkyl halide.
C. The rate is highest for tertiary alkyl halides due to carbocation stability.
D. The rate decreases as the steric hindrance around the electrophilic carbon increases.
☑ Correct Answer: D
☑ Explanation: SN2 reactions are highly sensitive to steric effects. The nucleophile must
approach from the backside, and bulky groups around the electrophilic carbon hinder this
attack. The rate order is methyl > primary > secondary >> tertiary (which generally do not
undergo SN2).
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[2] Which of the following reagents would be most effective for the selective reduction of a
ketone to a secondary alcohol in the presence of an ester?
A. LiAlH4 in ether
B. NaBH4 in ethanol
C. DIBAL-H in hexane at -78°C
D. H2 with Pd/C
☑ Correct Answer: B
☑ Explanation: NaBH4 is a mild reducing agent that selectively reduces ketones and
aldehydes to alcohols. It does not reduce esters, carboxylic acids, or amides under normal
conditions. LiAlH4 would reduce both the ketone and the ester. DIBAL-H is typically used to
reduce esters to aldehydes. H2/Pd/C reduces alkenes and alkynes.
[3] Consider the following reaction sequence: 1-bromobutane is treated with sodium cyanide
(NaCN) in DMSO, followed by reduction with LiAlH4, and then treatment with aqueous acid.
What is the final major organic product?
A. Butan-1-amine
B. Butan-2-amine
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C. Pentan-1-amine
D. 2-methylpropan-1-amine
☑ Correct Answer: C
☑ Explanation: 1-bromobutane undergoes SN2 reaction with NaCN to form pentanenitrile
(C4H9CN). LiAlH4 reduces the nitrile to a primary amine, yielding pentan-1-amine (C5H11N).
[4] Which diene and dienophile would be the most reactive in a Diels-Alder reaction?
A. A diene in the s-trans conformation and an electron-rich dienophile.
B. A diene in the s-cis conformation and an electron-poor dienophile.
C. A diene in the s-trans conformation and an electron-poor dienophile.
D. A diene in the s-cis conformation and an electron-rich dienophile.
☑ Correct Answer: B
☑ Explanation: For a Diels-Alder reaction to occur, the diene must be in the s-cis
conformation. The reaction is favored by an electron-donating group on the diene and an
electron-withdrawing group on the dienophile (normal electron demand).
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[5] What is the major product of the following reaction? 2-methylpropene + HBr in the
presence of peroxides (ROOR).
A. 1-bromo-2-methylpropane
B. 2-bromo-2-methylpropane
C. 1-bromo-1-methylpropane
D. 2-bromo-1-methylpropane
☑ Correct Answer: A
☑ Explanation: The addition of HBr to an alkene in the presence of peroxides proceeds via
an anti-Markovnikov radical mechanism. The bromine atom adds to the less substituted carbon,
resulting in 1-bromo-2-methylpropane.
[6] Which of the following compounds would undergo an SN1 reaction most rapidly?
A. Bromomethane
B. 2-bromopropane
C. 2-bromo-2-methylpropane
D. Bromobenzene
☑ Correct Answer: C
CHEM 210 Exam 5 | Advanced Organic Chemistry | In-
Depth Conceptual & Application-Based Questions | Graded
A+
[1] Which of the following statements best describes the relationship between the rate of an
SN2 reaction and the structure of the alkyl halide?
A. The rate increases as the steric hindrance around the electrophilic carbon increases.
B. The rate is independent of the structure of the alkyl halide.
C. The rate is highest for tertiary alkyl halides due to carbocation stability.
D. The rate decreases as the steric hindrance around the electrophilic carbon increases.
☑ Correct Answer: D
☑ Explanation: SN2 reactions are highly sensitive to steric effects. The nucleophile must
approach from the backside, and bulky groups around the electrophilic carbon hinder this
attack. The rate order is methyl > primary > secondary >> tertiary (which generally do not
undergo SN2).
,2
[2] Which of the following reagents would be most effective for the selective reduction of a
ketone to a secondary alcohol in the presence of an ester?
A. LiAlH4 in ether
B. NaBH4 in ethanol
C. DIBAL-H in hexane at -78°C
D. H2 with Pd/C
☑ Correct Answer: B
☑ Explanation: NaBH4 is a mild reducing agent that selectively reduces ketones and
aldehydes to alcohols. It does not reduce esters, carboxylic acids, or amides under normal
conditions. LiAlH4 would reduce both the ketone and the ester. DIBAL-H is typically used to
reduce esters to aldehydes. H2/Pd/C reduces alkenes and alkynes.
[3] Consider the following reaction sequence: 1-bromobutane is treated with sodium cyanide
(NaCN) in DMSO, followed by reduction with LiAlH4, and then treatment with aqueous acid.
What is the final major organic product?
A. Butan-1-amine
B. Butan-2-amine
,3
C. Pentan-1-amine
D. 2-methylpropan-1-amine
☑ Correct Answer: C
☑ Explanation: 1-bromobutane undergoes SN2 reaction with NaCN to form pentanenitrile
(C4H9CN). LiAlH4 reduces the nitrile to a primary amine, yielding pentan-1-amine (C5H11N).
[4] Which diene and dienophile would be the most reactive in a Diels-Alder reaction?
A. A diene in the s-trans conformation and an electron-rich dienophile.
B. A diene in the s-cis conformation and an electron-poor dienophile.
C. A diene in the s-trans conformation and an electron-poor dienophile.
D. A diene in the s-cis conformation and an electron-rich dienophile.
☑ Correct Answer: B
☑ Explanation: For a Diels-Alder reaction to occur, the diene must be in the s-cis
conformation. The reaction is favored by an electron-donating group on the diene and an
electron-withdrawing group on the dienophile (normal electron demand).
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[5] What is the major product of the following reaction? 2-methylpropene + HBr in the
presence of peroxides (ROOR).
A. 1-bromo-2-methylpropane
B. 2-bromo-2-methylpropane
C. 1-bromo-1-methylpropane
D. 2-bromo-1-methylpropane
☑ Correct Answer: A
☑ Explanation: The addition of HBr to an alkene in the presence of peroxides proceeds via
an anti-Markovnikov radical mechanism. The bromine atom adds to the less substituted carbon,
resulting in 1-bromo-2-methylpropane.
[6] Which of the following compounds would undergo an SN1 reaction most rapidly?
A. Bromomethane
B. 2-bromopropane
C. 2-bromo-2-methylpropane
D. Bromobenzene
☑ Correct Answer: C
