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CHEM 210 Exam 7 | Advanced Organic Chemistry | In-
Depth Conceptual, Application, and Scenario-Based
Questions | Graded A+
[1] A student is performing a synthesis and observes that the reaction of 1-bromobutane with
sodium methoxide in methanol yields a mixture of products. The major product is an ether, but
a significant amount of an alkene is also formed. Which of the following changes to the reaction
conditions would most effectively increase the ratio of the ether to the alkene?
A. Use a more sterically hindered alkoxide, such as potassium tert-butoxide.
B. Increase the temperature of the reaction.
C. Use a less polar solvent, such as acetone.
D. Use a lower concentration of the nucleophile.
☑ Correct Answer: C
☑ Explanation: The reaction proceeds via competing SN2 (ether) and E2 (alkene)
pathways. A less polar solvent favors the SN2 mechanism because it destabilizes the transition
state for the E2 reaction more than the SN2 reaction. A bulky base (A) favors E2. Increasing
temperature (B) favors elimination due to increased entropy. Lowering nucleophile
concentration (D) would disfavor both but slightly favor elimination.
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[2] Which of the following statements best explains why the Friedel-Crafts alkylation of anisole
with 2-chlorobutane in the presence of AlCl3 results in a mixture of ortho and para products,
but also leads to a significant amount of rearranged alkyl groups?
A. Anisole is deactivated towards electrophilic aromatic substitution.
B. The methoxy group is a meta-directing group.
C. The alkyl group from 2-chlorobutane undergoes rearrangement to a more stable carbocation
before attacking the ring.
D. The reaction proceeds via a radical mechanism.
☑ Correct Answer: C
☑ Explanation: Friedel-Crafts alkylations are prone to rearrangements because the initial
carbocation can rearrange to a more stable one (e.g., from a secondary to a tertiary
carbocation) via hydride or alkyl shifts. This rearranged carbocation then attacks the ring.
Anisole is activated and ortho/para directing (A, B are incorrect). The mechanism is electrophilic,
not radical (D).
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[3] A compound with the molecular formula C5H10O2 shows a strong IR absorption at 1740
cm⁻¹ and a 'H NMR spectrum with a triplet at δ 1.1 ppm (3H), a singlet at δ 2.0 ppm (3H), and a
quartet at δ 4.1 ppm (2H). What is the most likely structure of this compound?
A. Pentanoic acid
B. Ethyl acetate
C. Methyl butanoate
D. Propyl acetate
☑ Correct Answer: B
☑ Explanation: The IR band at 1740 cm⁻¹ indicates an ester carbonyl. The 'H NMR shows a
triplet (3H) for a CH3 adjacent to a CH2, a singlet (3H) for a CH3 adjacent to a carbonyl, and a
quartet (2H) for a CH2 adjacent to an oxygen. This fits ethyl acetate (CH3COOCH2CH3).
[4] In a set of experiments, a chemist is studying the solvolysis of 2-bromo-2-methylpropane in
different solvents. In which solvent would the reaction be expected to proceed fastest?
A. 100% water
B. 80% ethanol / 20% water
C. 50% ethanol / 50% water
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D. 100% ethanol
☑ Correct Answer: A
☑ Explanation: This is an SN1 reaction where the rate-determining step is the ionization of
the alkyl halide to form a carbocation. Polar protic solvents stabilize the carbocation and the
leaving group through solvation. Water is more polar and a better ionizing solvent than ethanol.
A higher percentage of water increases the solvent's ionizing power, thus accelerating the rate.
[5] Consider the following reaction sequence: Benzene is treated with 1-chloropropane in the
presence of AlCl3, followed by reaction with Cl2 in the presence of FeCl3, and finally treated
with KMnO4 (hot, concentrated). What is the final major organic product?
A. 1-chloro-3-propylbenzene
B. 3-chlorobenzoic acid
C. 4-chlorobenzoic acid
D. Benzoic acid
☑ Correct Answer: D
☑ Explanation: The first step is Friedel-Crafts alkylation, yielding propylbenzene. The
CHEM 210 Exam 7 | Advanced Organic Chemistry | In-
Depth Conceptual, Application, and Scenario-Based
Questions | Graded A+
[1] A student is performing a synthesis and observes that the reaction of 1-bromobutane with
sodium methoxide in methanol yields a mixture of products. The major product is an ether, but
a significant amount of an alkene is also formed. Which of the following changes to the reaction
conditions would most effectively increase the ratio of the ether to the alkene?
A. Use a more sterically hindered alkoxide, such as potassium tert-butoxide.
B. Increase the temperature of the reaction.
C. Use a less polar solvent, such as acetone.
D. Use a lower concentration of the nucleophile.
☑ Correct Answer: C
☑ Explanation: The reaction proceeds via competing SN2 (ether) and E2 (alkene)
pathways. A less polar solvent favors the SN2 mechanism because it destabilizes the transition
state for the E2 reaction more than the SN2 reaction. A bulky base (A) favors E2. Increasing
temperature (B) favors elimination due to increased entropy. Lowering nucleophile
concentration (D) would disfavor both but slightly favor elimination.
,2
[2] Which of the following statements best explains why the Friedel-Crafts alkylation of anisole
with 2-chlorobutane in the presence of AlCl3 results in a mixture of ortho and para products,
but also leads to a significant amount of rearranged alkyl groups?
A. Anisole is deactivated towards electrophilic aromatic substitution.
B. The methoxy group is a meta-directing group.
C. The alkyl group from 2-chlorobutane undergoes rearrangement to a more stable carbocation
before attacking the ring.
D. The reaction proceeds via a radical mechanism.
☑ Correct Answer: C
☑ Explanation: Friedel-Crafts alkylations are prone to rearrangements because the initial
carbocation can rearrange to a more stable one (e.g., from a secondary to a tertiary
carbocation) via hydride or alkyl shifts. This rearranged carbocation then attacks the ring.
Anisole is activated and ortho/para directing (A, B are incorrect). The mechanism is electrophilic,
not radical (D).
,3
[3] A compound with the molecular formula C5H10O2 shows a strong IR absorption at 1740
cm⁻¹ and a 'H NMR spectrum with a triplet at δ 1.1 ppm (3H), a singlet at δ 2.0 ppm (3H), and a
quartet at δ 4.1 ppm (2H). What is the most likely structure of this compound?
A. Pentanoic acid
B. Ethyl acetate
C. Methyl butanoate
D. Propyl acetate
☑ Correct Answer: B
☑ Explanation: The IR band at 1740 cm⁻¹ indicates an ester carbonyl. The 'H NMR shows a
triplet (3H) for a CH3 adjacent to a CH2, a singlet (3H) for a CH3 adjacent to a carbonyl, and a
quartet (2H) for a CH2 adjacent to an oxygen. This fits ethyl acetate (CH3COOCH2CH3).
[4] In a set of experiments, a chemist is studying the solvolysis of 2-bromo-2-methylpropane in
different solvents. In which solvent would the reaction be expected to proceed fastest?
A. 100% water
B. 80% ethanol / 20% water
C. 50% ethanol / 50% water
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D. 100% ethanol
☑ Correct Answer: A
☑ Explanation: This is an SN1 reaction where the rate-determining step is the ionization of
the alkyl halide to form a carbocation. Polar protic solvents stabilize the carbocation and the
leaving group through solvation. Water is more polar and a better ionizing solvent than ethanol.
A higher percentage of water increases the solvent's ionizing power, thus accelerating the rate.
[5] Consider the following reaction sequence: Benzene is treated with 1-chloropropane in the
presence of AlCl3, followed by reaction with Cl2 in the presence of FeCl3, and finally treated
with KMnO4 (hot, concentrated). What is the final major organic product?
A. 1-chloro-3-propylbenzene
B. 3-chlorobenzoic acid
C. 4-chlorobenzoic acid
D. Benzoic acid
☑ Correct Answer: D
☑ Explanation: The first step is Friedel-Crafts alkylation, yielding propylbenzene. The
