Deck 11: Radical Reactions

Question 1

Use correct arrow formalism to show the mechanism of the following radical process:

Answer 1

Question 2

Use correct arrow formalism to show the mechanism of the following radical process:

Answer 2

Question 3

Use correct arrow formalism to draw all of the reasonable resonance structures for the radical shown below.

Answer 3

Question 4

Which of the following is the most stable radical?

A)
B)
C)
D)
E)

Question 5

Which term most accurately describes the process shown below?

A) coupling
B) proton transfer
C) halogen abstraction
D) hydrogen abstraction
E) homolytic cleavage

Question 6

Rank the following radicals in order of decreasing stability (most stable to least stable).

A) IV > I > II > III
B) III > I > II > IV
C) III > II > I > IV
D) III > IV > II > I
E) II > III > I > IV

Question 7

Which of the following is an example of termination?

A)
B)
C)
D)
E)

Question 8

Using correct arrow formalism, draw all of the reasonable resonance structures for the radical shown below.

Question 9

Which term most accurately describes the process shown below?

A) hydrogen abstraction
B) halogen abstraction
C) homolytic cleavage
D) coupling
E) elimination

Question 10

Use correct arrow formalism to show the mechanism of the following radical process:

Question 11

In the molecule shown below, determine which of the highlighted C-H bonds (from a to e) is expected to have the lowest bond dissociation energy.

A) C-H_a
B) C-H_b
C) C-H_c
D) C-H_d
E) C-H_e

Question 12

A bromine radical can add to the $\pi$ bond of 2-methylpropene. Use correct arrow formalism to show this process and the expected result.

Question 13

Which of the following are the products of a homolytic cleavage of a C-C bond of ethane?

A)
B)
C)
D)

Question 14

Which term most accurately describes the process shown below?

A) coupling
B) hydrogen abstraction
C) halogen abstraction
D) homolytic cleavage
E) addition to a $\pi$ bond

Question 15

Which of the labeled C-H bonds is the weakest?

A) C-H_a
B) C-H_b
C) C-H_c
D) C-H_d
E) C-H_e

Question 16

Use correct arrow formalism consistent with the following radical process:

Question 17

Use correct arrow formalism to show a homolytic bond cleavage of ethane to produce two methyl radicals.

Question 18

Which term most accurately describes the process shown below?

A) coupling
B) elimination
C) halogen abstraction
D) hydrogen abstraction
E) homolytic cleavage

Question 19

Rank the following radicals in order of decreasing stability (most stable to least stable).

A) IV > I > II > III
B) III > I > II > IV
C) III > II > I > IV
D) III > IV > II > I
E) II > I > III > IV

Question 20

Which of the following is an example of initiation?

A)
B)
C)
D)
E)

Question 21

Use correct arrow formalism to show the propagation steps in the chlorination of propane to produce 2-chloropropane.

Question 22

Which of the following would you expect to function as an initiator at the lowest temperature?

A)

B) Cl₂

C)

D)

Question 23

Predict the major product(s) of the following reaction.

Question 24

Which of the following is the correct name for the major product of the following reaction?

A) (R)-3-bromo-3-ethylbutane
B) (S)-3-bromo-3-ethylbutane
C) (R)-3-bromo-3-methylpentane
D) (S)-3-bromo-3-methylpentane
E) 3-bromo-3-methylpentane

Question 25

Predict the major product(s) of the following reaction.

Question 26

Which of the following correctly describes the nature of the transition state of the rate-determining step of the free-radical bromination of methane?

A) the transition state resembles the reactants more than the products
B) the transition state resembles the products more than the reactants
C) the transition state equally resembles products and reactants

Question 27

Cyclic compound A has molecular formula C₅H₁₀ and undergoes monochlorination to yield exactly three different constitutional isomers. Identify compound A and show the monochlorination products.

Question 28

Free radical chlorination of ethane can produce higher halogenation products (dichlorinated, trichlorinated, etc…) in addition to chloroethane. How could the production of higher halogenated products be minimized?

A) Use an excess of chlorine
B) Use an excess of ethane
C) Use equimolar chlorine and ethane
D) It is not possible to minimize the production of higher halogenated products

Question 29

Both compounds A and B have molecular formula C₆H₁₄. Monochlorination of compound A results in formation of two constitutional isomers. Monochlorination of compound B results in formation of four constitutional isomers. Identify compounds A and B, and show the products of each monochlorination.

Question 30

Which of the following is most reactive towards chlorination?

A) methane
B) chloromethane
C) dichloromethane
D) chloroform
E) ethane

Question 31

Predict the major product(s) of the following reaction:

A)
B)
C)
D)

Question 32

Which of the following is the rate-determining step in the free-radical bromination of methane?

A)
B)
C)
D)

Question 33

Which of the following are possible termination steps in the chlorination of methane?

A)
B)
C)
D)

Question 34

Which of the following shows the initiation step of monochlorination of methane?

A) I
B) II
C) III
D) IV
E) I and II

Question 35

Predict the major product(s) of the following reaction.

A) I
B) II and IV
C) III and V
D) I and IV
E) V

Question 36

Predict the major product obtained upon radical bromination of t-butylcyclohexane.

A) 1-bromo-1-tert-butylcyclohexane
B) 2-bromo-1-tert-butylcyclohexane
C) 3-bromo-1-tert-butylcyclohexane
D) 4-bromo-1-tert-butylcyclohexane
E) (1-bromo-1,1-dimethyl)ethylcyclohexane

Question 37

Which of the following processes is responsible for the fact that free radical bromination of methane is slower than free radical chlorination?

A) initiation
B) hydrogen abstraction
C) halogen abstraction
D) termination
E) entropy

Question 38

Predict the major product of the following reaction:

A)
B)
C)
D)

Question 39

How many constitutional isomers are possible if propane is dichlorinated? Draw them.

Question 40

Which of the following represents a propagation step in the monochlorination of methylene chloride (CH₂Cl₂)?

A)

B)Cl₂

C)

D)

Question 41

Upon treatment with NBS and irradiation with UV light, 2-methyl-2-butene reacts to produce exactly six monobrominated compounds. Draw the products of this reaction.

Question 42

Upon treatment of 1-methylcyclopentene with NBS and irradiation with UV light, exactly nine compounds (including stereoisomers) are formed. Draw all nine products.

Question 43

Predict the major product(s) of the following reaction.

A) I
B) I and II
C) I, II, and III
D) I, II, III
E) IV

Question 44

Which of the following shows the correct products initially formed (first step) when ozone absorbs ultraviolet light?

A)
B)
C)
D)

Question 45

Use correct arrow formalism to show the second propagation step for the reaction of a chlorine radical with ozone.

Question 46

Draw the major product(s) of the following reaction. Is the product optically active? Explain.

Question 47

Which term best describes the process shown below?

A) neutralization
B) propagation
C) termination
D) initiation
E) elimination

Question 48

Which of the following compounds would be expected to be least destructive to the ozone layer?

A)
B)
C)
D)

Question 49

Compound A has molecular formula C₉H₂₀. Compound A produces exactly three constitutional isomers upon monochlorination, and one major constitutional isomer upon monobromination. Which of the following are possible structures of compound A?

Question 50

Which of the following is expected to be a major product for the reaction shown below?

A) I
B) II
C) III
D) IV

Question 51

What reagents would best accomplish the following transformation?

A) Br₂
B) PBr₃
C) CH₃Br
D) NBS, heat

Question 52

Use correct arrow formalism to show the propagation steps for the autooxidation of diethyl ether.

Question 53

Upon treatment with NBS and irradiation with UV light, 1-ethyl-4-methylbenzene produces exactly three monobrominated compounds (including stereoisomers). Draw the products of this reaction.

Question 54

Upon treatment with NBS and irradiation with UV light, 2-propyl-1-pentene produces exactly four monobrominated compounds (including stereoisomers). Draw and name the products of this reaction.

Question 55

Which of the following are possible product(s) of the reaction shown?

A) I
B) I, II
C) I, II, IV, V
D) I, III, IV, V
E) I, II, III, IV, IV

Question 56

Which of the following are major products of the reaction shown?

A) I
B) I, II
C) I, IV
D) I, III
E) I, II, III, IV

Question 57

Draw the major product(s) of the following reaction. Is the product optically active? Explain.

Question 58

Which of the following is (are) the likely major product(s) of the reaction shown?

A) I
B) II
C) III
D) I and III
E) I and IV

Question 59

Which of the following is expected to function as an antioxidant?

A) I
B) II
C) III
D) IV
E) I, II, III, and IV

Question 60

Upon treatment with NBS and irradiation with UV light, 2-isopropyl-3-methyl-1-butene reacts to produce exactly two monobrominated compounds. Draw the products of this reaction.

Question 61

Thermal cracking of butane can produce ethyl radicals via homolytic cleavage. Use correct arrow formalism to show this process.

Question 62

Predict the major product(s) of the reaction shown below:

A) I
B) II
C) III
D) IV
E) II and III

Question 63

Which term best describes the process shown below?

A) initiation
B) propagation
C) termination
D) elimination
E) inhibition

Question 64

Your textbook mentions that the free radical polymerization of ethylene can produce branches. Although branches of various lengths are possible, butyl branches are very common. Suggest an explanation for this fact.

Question 65

One possible product of thermal cracking of hexane is 1-butene. Use correct arrow formalism to suggest a possible mechanism for this process starting from an alkyl radical.

Question 66

Predict the major product(s) of the reaction shown below:

A) I
B) II
C) III
D) IV
E) II and III

Question 67

Predict the product(s) of the following reaction:

A) I
B) II
C) III
D) I, II
E) I, II, III, IV

Question 68

The free radical polymerization of styrene with benzoyl peroxide yields a polymer that has repeat units arranged primarily in a 'head-to-tail' arrangement. This means that the phenyl group primarily ends up placed at alternating carbon atoms along the chain. Use correct arrow formalism to show why this arrangement is preferred over a 'head-to-head' or 'tail-to-tail' arrangement.

Question 69

Azobisisobutyronitrile (AIBN) is commonly used as a radical initiator. Use correct arrow formalism to show this process.

Question 70

Which monomer is used for the synthesis of Teflon?

A) 1,1-difluoroethene
B) 1,1,2,2-tetrafluoropropene
C) 1,1,2,2-tetrafluoroethene
D) tetrafluoromethane

Question 71

Predict the product(s) of the following reaction:

A) I
B) II
C) III
D) I, II
E) I, II, III, IV

Question 72

Which intermediate leads to the major product for the reaction of 2-methyl-2-butene with hydrogen bromide?

A) I
B) II
C) III
D) IV
E) None of the above

Question 73

Use correct arrow formalism to show termination by coupling of two growing poly(vinyl chloride) chains.

Question 74

Draw the product of coupling of the following radicals.

Question 75

Of the four choices shown, which is likely to be a major product of the reaction below?

A) I
B) II
C) III
D) IV

Question 76

Which intermediate leads to the major product for the reaction of 2-methyl-2-butene with hydrogen bromide and hydrogen peroxide?

A) I
B) II
C) III
D) IV

Question 77

Which monomer is used for the synthesis of poly(vinyl chloride)?

A) 1-chloroethene
B) 1-chloroethane
C) 1,2-dichloroethene
D) 1-chloro-1-propene

Question 78

Which of the following steps is thermodynamically unfavorable at all temperatures?

A)
B)
C)
D)

Question 79

Compound A, C₆H₁₂ reacts with HBr/ROOR to give compound B, C₆H₁₃Br. Compound C, C₆H₁₄, reacts with bromine and light to produce compound B, C₆H₁₃Br. Suggest structures for compounds A, B, and C.

Question 80

Propylene (propene) undergoes free radical polymerization with benzoyl peroxide, but does not produce very long chains. Provide a reasonable explanation for this result.