Exam 4: The Study of Chemical Reactions

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?

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Question 21

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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Question 22

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

(Multiple Choice)

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Question 23

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

(Multiple Choice)

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Question 24

Which is a measure of the randomness of a system?

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Question 25

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

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Question 26

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

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Question 27

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

(Multiple Choice)

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Question 28

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

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Question 29

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

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Question 30

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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Question 31

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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Question 32

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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Question 33

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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Question 34

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

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Question 35

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

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Question 36

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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Question 37

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

(Multiple Choice)

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Question 38

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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Question 39

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

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Question 40

Showing 21 - 40 of 128

Exam 4: The Study of Chemical Reactions

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?

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)

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

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

Which is a measure of the randomness of a system?

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

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

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

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

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

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

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.

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)?

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∙

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

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

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 ________.

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

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?

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

Structure and Bonding

Acids and Bases; Functional Groups

Structure and Stereochemistry of Alkanes

Stereochemistry

Alkyl Halides; Nucleophilic Substitution

Structure and Synthesis of Alkenes; Elimination

Reactions of Alkenes

Structure and Synthesis of Alcohols

Reactions of Alcohols

Infrared Spectroscopy and Mass Spectrometry

Nuclear Magnetic Resonance Spectroscopy

Ethers, Epoxides, and Thioethers

Conjugated Systems, Orbital Symmetry, and Ultraviolet Spectroscopy

Aromatic Compounds

Reactions of Aromatic Compounds

Ketones and Aldehydes

Amines

Carboxylic Acids

Carboxylic Acid Derivatives

Condensations and Alpha Substitutions of Carboxyl Compounds

Carbohydrates and Nucleic Acids

Amino Acids, Peptides, and Proteins

Lipids

Synthetic Polymers

Filters

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)

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

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

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

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.

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∙

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 .

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?