Question 1

List the following radicals in order of increasing stability (i.e., from least stable to most stable).
(CH3)3C∙, CH2  
CHCH2∙, CH3CH2∙, CH3∙, (CH3)2CH∙

Accepted Answer

CH₃∙ < CH₃CH...

Question 2

Rank the following carbocations in order of stability. (The most stable is first.)   III > II B)  II > I > III C)  III > I > II D)  I > II > III" class="answers-bank-image d-inline" rel="preload" >

Accepted Answer

A)   I > III > II
B)   II > I > III
C)   III > I > II
D)   I > II > IIIE) A) and B)
F) All of the above

Question 3

The hydrogenation of acetylene to produce ethane is shown below. Is ΔS° for this reaction positive, negative, or impossible to predict? Explain your reasoning.
C2H2 (g) + 2H2 (g) → C2H6 (g)

Accepted Answer

ΔS° < 0. The three reactant mo...

Question 4

What is the name of the major monobrominated product which results when methylcyclohexane is subjected to Br2/hν conditions?

Accepted Answer

1-bromo-1-...

Question 5

What is the relative reactivity of 2° vs 1° hydrogens in the free radical bromination of n-butane if the ratio of 1-bromobutane to 2-bromobutane formed is 7:93?

Accepted Answer

The 2° hydrogens are...

Question 6

Which of the two 2° radicals below is more stable and why?

Accepted Answer

A is more stable because it ha...

Question 7

Which of the following reactive intermediates can best be described as both nucleophilic and strongly basic?

Accepted Answer

A)   carbanions
B)   carbocations
C)   carbenes
D)   free radicals
E)   alkanesF) C) and D)
G) A) and B)

Question 8

How many distinct dichlorination products can result when isobutane is subjected to free radical chlorination?

Accepted Answer

A)   1
B)   2
C)   3
D)   4
E)   6F) B) and E)
G) C) and E)

Question 9

Which of the following statements is the best statement of the Hammond Postulate?

Accepted Answer

A)   In an endothermic reaction, the transition state is closer to the reactants in structure.
B)   In an exothermic reaction, the transition state is closer in energy to the products.
C)   Related species that are similar in energy are also similar in structure.
D)   The structure of the transition state in an organic reaction is always modeled on the structure of the reactants leading to that transition state.
E)   Transition states are molecular species of finite lifetime whose properties can be probed through free radical reactions.F) B) and E)
G) A) and D)

Question 10

Consider the reaction of A being converted into B at 25°C. If the ΔG° of this reaction is eq is ________ and the % conversion is ________. A)  0.18; 15% B)  0.43; 30% C)  1.0; 50% D)  2.3; 70% E)  5.4; 84%" class="answers-bank-image d-inline" rel="preload" > the Keq is ________ and the % conversion is ________.

Accepted Answer

A)   0.18; 15%
B)   0.43; 30%
C)   1.0; 50%
D)   2.3; 70%
E)   5.4; 84%F) B) and C)
G) A) and C)

Question 11

Which is a measure of the randomness of a system?

Accepted Answer

A)   entropy
B)   enthalpy
C)   free energy
D)   halogenation
E)   stoichiometryF) A) and C)
G) A) and B)

Question 12

Draw the important resonance form/s of the following free radical.

Accepted Answer

The answer of Draw the important resonance form/s of the...

Question 13

Which of the following correctly expresses the standard Gibbs free energy change of a reaction in terms of the reaction temperature (T)  and equilibrium constant (K) ?

Accepted Answer

A)   ΔG° = e-K/RT
B)   ΔG° = eK/RT
C)   ΔG° = RTlnK
D)   ΔG° = -RTlnK
E)   none of the aboveF) C) and D)
G) A) and B)

Question 14

Given the bond dissociation energies below (in kcal/mol), calculate the overall ΔH° for the following reaction:
(CH3)3CH + Br2 → (CH3)3CBr + HBr
(CH3)3C-H 91
(CH3)3C-Br 65
Br-Br 46
H-Br 88
CH3-Br 70

Accepted Answer

Question 15

Provide the two propagation steps in the free-radical chlorination of ethane.

Accepted Answer

CH₃CH₃ + Cl∙ → CH₃CH₂∙ +...

Question 16

Consider the three-step mechanism for the reaction of A through intermediates B and C to produce D shown below.
A → B Ea = 15 kcal/mol, ΔH° = 13 kcal/mol
B → C Ea = 10 kcal/mol, ΔH° = -6 kcal/mol
C → D Ea = 2 kcal/mol, ΔH° = -20 kcal/mol
Which of the three steps is rate-limiting?

Accepted Answer

A)   The reaction of A to B.
B)   The reaction of B to C.
C)   The reaction of C to D.
D)   All three steps occur at the same rate; there is no rate-limiting step.
E)   The most exothermic step is rate-limiting.F) A) and C)
G) B) and E)

Question 17

When Br radical reacts with 1-butene (CH3CH2CH=CH2), the hydrogen atom which is preferentially abstracted is the one which produces a resonance stabilized radical. Draw the major resonance contributing forms of this radical.

Accepted Answer

CH₃

HCH

...

Question 18

Given the pKa values for the two acids below, what would you expect the Keq for this reaction to be? a values for the two acids below, what would you expect the Keq for this reaction to be?   A)  Keq > 1 B)  Keq = 1 C)  Keq

Accepted Answer

A)   Keq > 1
B)   Keq = 1
C)   Keq 
D)   You can't tell from the information given.E) C) and D)
F) A) and B)

Question 19

________ is the minimum kinetic energy reacting molecules must possess to overcome the repulsions between their electron clouds when they collide.

Accepted Answer

The activa...

Question 20

Which of the following is not a possible termination step in the free radical chlorination of methane?

Accepted Answer

A)   ∙CH3 + Cl2 → CH3Cl + Cl∙
B)   ∙CH3 + Cl∙ → CH3Cl
C)   ∙CH3 + ∙CH3 → CH3CH3
D)   ∙CH3 + wall → CH3-wall
E)   Cl∙ + wall → Cl-wallF) C) and D)
G) C) and E)

Exam 4: The Study of Chemical Reactions

Which is a measure of the randomness of a system?

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The hydrogenation of acetylene to produce ethane is shown below. Is ΔS° for this reaction positive, negative, or impossible to predict? Explain your reasoning. C2H2 (g) + 2H2 (g) → C2H6 (g)

Correct AnswerverifiedΔS° < 0. The three reactant mo...View AnswerShow Answer

________ is the minimum kinetic energy reacting molecules must possess to overcome the repulsions between their electron clouds when they collide.

Correct AnswerverifiedThe activa...View AnswerShow Answer

Which of the following reactive intermediates can best be described as both nucleophilic and strongly basic?

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Which of the following is not a possible termination step in the free radical chlorination of methane?

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How many distinct dichlorination products can result when isobutane is subjected to free radical chlorination?

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Given the pKa values for the two acids below, what would you expect the Keq for this reaction to be?

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Consider the reaction of A being converted into B at 25°C. If the ΔG° of this reaction is the Keq is ________ and the % conversion is ________.

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Rank the following carbocations in order of stability. (The most stable is first.)

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What is the relative reactivity of 2° vs 1° hydrogens in the free radical bromination of n-butane if the ratio of 1-bromobutane to 2-bromobutane formed is 7:93?

Correct AnswerverifiedThe 2° hydrogens are...View AnswerShow Answer

What is the name of the major monobrominated product which results when methylcyclohexane is subjected to Br2/hν conditions?

Correct Answerverified1-bromo-1-...View AnswerShow Answer

Given the bond dissociation energies below (in kcal/mol), calculate the overall ΔH° for the following reaction: (CH3)3CH + Br2 → (CH3)3CBr + HBr (CH3)3C-H 91 (CH3)3C-Br 65 Br-Br 46 H-Br 88 CH3-Br 70

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Which of the following statements is the best statement of the Hammond Postulate?

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Consider the three-step mechanism for the reaction of A through intermediates B and C to produce D shown below. A → B Ea = 15 kcal/mol, ΔH° = 13 kcal/mol B → C Ea = 10 kcal/mol, ΔH° = -6 kcal/mol C → D Ea = 2 kcal/mol, ΔH° = -20 kcal/mol Which of the three steps is rate-limiting?

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When Br radical reacts with 1-butene (CH3CH2CH=CH2), the hydrogen atom which is preferentially abstracted is the one which produces a resonance stabilized radical. Draw the major resonance contributing forms of this radical.

Correct AnswerverifiedCH3 HCH ...View AnswerShow Answer

Provide the two propagation steps in the free-radical chlorination of ethane.

Correct AnswerverifiedCH3CH3 + Cl∙ → CH3CH2∙ +...View AnswerShow Answer

Draw the important resonance form/s of the following free radical.

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Which of the following correctly expresses the standard Gibbs free energy change of a reaction in terms of the reaction temperature (T) and equilibrium constant (K) ?

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Which of the two 2° radicals below is more stable and why?

Correct AnswerverifiedA is more stable because it ha...View AnswerShow Answer

List the following radicals in order of increasing stability (i.e., from least stable to most stable). (CH3)3C∙, CH2 CHCH2∙, CH3CH2∙, CH3∙, (CH3)2CH∙

Correct AnswerverifiedCH3∙ < CH3CH...View AnswerShow Answer

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The hydrogenation of acetylene to produce ethane is shown below. Is ΔS° for this reaction positive, negative, or impossible to predict? Explain your reasoning. C₂H₂ (g) + 2H₂ (g) → C₂H₆ (g)

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ΔS° < 0. The three reactant mo...
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The activa...
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Given the pK_a values for the two acids below, what would you expect the K_eq for this reaction to be?

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Consider the reaction of A being converted into B at 25°C. If the ΔG° of this reaction is the K_eq is and the % conversion is .

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The 2° hydrogens are...
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What is the name of the major monobrominated product which results when methylcyclohexane is subjected to Br₂/hν conditions?

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1-bromo-1-...
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Given the bond dissociation energies below (in kcal/mol), calculate the overall ΔH° for the following reaction: (CH₃)₃CH + Br₂→ (CH₃)₃CBr + HBr (CH₃)₃C-H 91 (CH₃)₃C-Br 65 Br-Br 46 H-Br 88 CH₃-Br 70

Correct Answer
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Correct Answer
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Consider the three-step mechanism for the reaction of A through intermediates B and C to produce D shown below. A → B E_a = 15 kcal/mol, ΔH° = 13 kcal/mol B → C E_a = 10 kcal/mol, ΔH° = -6 kcal/mol C → D E_a = 2 kcal/mol, ΔH° = -20 kcal/mol Which of the three steps is rate-limiting?

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When Br radical reacts with 1-butene (CH₃CH₂CH=CH₂), the hydrogen atom which is preferentially abstracted is the one which produces a resonance stabilized radical. Draw the major resonance contributing forms of this radical.

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CH₃
HCH ...
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CH₃CH₃ + Cl∙ → CH₃CH₂∙ +...
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A is more stable because it ha...
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List the following radicals in order of increasing stability (i.e., from least stable to most stable). (CH₃)₃C∙, CH₂ CHCH₂∙, CH₃CH₂∙, CH₃∙, (CH₃)₂CH∙

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CH₃∙ < CH₃CH...
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