Deck 10: Radical Reactions

Question 1

For which of the following reactions would the transition state most resemble the products? The following bond dissociation energies may be useful. (CH₃)₂CH-H CH₃CH₂CH₂-H H-F
(413 kJ mol^-1) (423 kJ mol^-1) (570 kJ mol^-1)
H-Cl H-Br
(432 kJ mol^-1) (366 kJ mol^-1)

A)

B) CH₃CH₂CH₃ + F· $\rightarrow$ CH₃CH₂CH₂· + HF
C)

D) CH₃CH₂CH₃ + Cl· $\rightarrow$ CH₃CH₂CH₂· + HCl
E) CH₃CH₂CH₃ + Br· $\rightarrow$ CH₃CH₂CH₂· + HBr

Answer 1

CH₃CH₂CH₃ + Br· $\rightarrow$ CH₃CH₂CH₂· + HBr

Question 2

Which of the reactions listed below would be exothermic?

A) CH₃-CH₃ $\rightarrow$ 2CH₃·
B) CH₃· + CH₄ $\rightarrow$ CH₄ + CH₃·
C) 2(CH₃)₂CH· $\rightarrow$ (CH₃)₂CH-CH(CH₃)₂
D) H· + (CH₃)₃CH $\rightarrow$ (CH₃)₃CH + H·
E) None of the above

Answer 2

2(CH₃)₂CH· $\rightarrow$ (CH₃)₂CH-CH(CH₃)₂

Question 3

How many different monochlorobutanes (including stereoisomers)are formed in the free radical chlorination of butane?

A) 1
B) 2
C) 3
D) 4
E) 5

Answer 3

3

Question 4

A chain reaction is one that:

A) involves a series of steps.
B) involves two steps of equal activation energy.
C) is one that can be initiated by light.
D) involves a series of steps,each of which generates a reactive intermediate that brings about the next step.
E) involves free radicals that have an unusual stability and thereby cause a large quantum yield.

Question 5

Which of the reactions listed below would have a value of $\Delta$ H° equal to zero?

A) H-H $\rightarrow$ 2H·
B) H· + CH₃-H $\rightarrow$ CH₃-H + H·
C) CH₃· + CH₃· $\rightarrow$ CH₃-CH₃
D) CH₃· + CH₃-H $\rightarrow$ CH₃-H + CH₃·
E) Reactions (B)and (D)

Question 6

The bond dissociation energies for the relevant bonds are given below each of the species involved in the following reaction.Calculate the overall $\Delta$ H° for the reaction.

A) +437 kJ / mol
B) -437 kJ / mol
C) -411 kJ / mol
D) +26 kJ / mol
E) -1581 kJ / mol

Question 7

Which of the following free radicals is the most stable?

A)

B)

C)

D)

E)

Question 8

Which of these molecules is not expected to arise as a product of the high temperature chlorination of methane?

A) CCl₄
B) HCCl₃
C) CH₂Cl₂
D) CH₃CH₃
E) CH₂=CH₂

Question 9

The reaction of Cl₂ with a methyl radical has a positive $\Delta$ H°.Which of these drawings is the best representation of the transition state of this reaction?

A)

B)

C)

D)

E)

Question 10

The bond dissociation energies for the relevant bonds are given below each of the species involved in the following reaction.Calculate the overall $\Delta$ H° for the reaction.

A) +243 kJ / mol
B) -138 kJ / mol
C) +138 kJ / mol
D) -781 kJ / mol
E) +781 kJ / mol

Question 11

If chlorocyclopentane were chlorinated to form all possible dichloro compounds and the product mixture subjected to precise fractional distillation,how many fractions would be obtained (ideally)?

A) 3
B) 4
C) 5
D) 7
E) 9

Question 12

The bond dissociation energies for the relevant bonds are given below each of the species involved in the following reaction.Calculate the overall $\Delta$ H° for the reaction.

A) -121 kJ / mol
B) +121 kJ / mol
C) +243 kJ / mol
D) +664 kJ / mol
E) -785 kJ / mol

Question 13

The bond dissociation energies for the relevant bonds are given below each of the species involved in the following reaction.Calculate the overall $\Delta$ H° for the reaction.

A) +616 kJ / mol
B) -101 kJ / mol
C) -173 kJ / mol
D) +57 kJ kJ / mol
E) -44 kJ / mol

Question 14

Which of the following gas-phase reactions is a possible chain-terminating step in the light-initiated chlorination of methane?

A) Cl-Cl $\rightarrow$ 2Cl·
B) Cl· + CH₄ $\rightarrow$ CH₃· + H-Cl
C) CH₃· + CH₃· $\rightarrow$ CH₃-CH₃
D) CH₃· + Cl-Cl $\rightarrow$ CH₃Cl + Cl·
E) More than one of the above

Question 15

Which of the reactions listed below would be exothermic?

A) H-H $\rightarrow$ 2H·
B) H· + CH₃-H $\rightarrow$ CH₃-H + H·
C) CH₃· + CH₃· $\rightarrow$ CH₃-CH₃
D) CH₃· + CH₃-H $\rightarrow$ CH₃-H + CH₃·
E) All of the above

Question 16

The reaction of 2-methylbutane with chlorine would yield how many monochloro derivatives? (include stereoisomers)

A) 2
B) 3
C) 4
D) 5
E) 6

Question 17

In the presence of light,ethane (1 mol)reacts with chlorine (1 mol)to form which product(s)?

A) CH₂ClCHCl₂
B) CH₃CHCl₂
C) CH₃CH₂Cl
D) ClCH₂CH₂Cl
E) All of these

Question 18

The $\Delta$ H° value is expected to be least for which indicated C-H bond of isopentane?

A)

B)

C)

D)

E)

Question 19

Hydrogen atom abstraction from which position would yield the most stable free radical intermediate during the reaction of bromine with 2,2,3-trimethylpentane?

A) C1
B) C2
C) C3
D) C4
E) C5

Question 20

An alternate mechanism for the chlorination of methane is: Cl₂ $\rightarrow$ 2Cl·
Cl-Cl, $\Delta$ H° = 243 kJ mol^-1
Cl· + CH₄ $\rightarrow$ CH₃Cl + H·
CH₃-H, $\Delta$ H° = 440 kJ mol^-1
H· + Cl₂ $\rightarrow$ HCl + Cl·
CH₃-Cl, $\Delta$ H° = 352 kJ mol^-1
H-Cl, $\Delta$ H° = 432 kJ mol ^-1
This mechanism is unlikely because:

A) The overall $\Delta$ H° is highly endothermic.
B) The probability factor is low.
C) One of the chain propagating steps is non-productive.
D) One of the chain propagating steps has a very high E_act.
E) One of the chain propagating steps is highly exothermic.

Question 21

In the presence of light at 25°C,isobutane (1 mol)and bromine (1 mol)yield which monobromo product(s)?

A) 2-Methyl-1-bromopropane (almost exclusively)
B) 2-Methyl-2-bromopropane (almost exclusively)
C) A mixture of 50% (A)and 50% (B)
D) A mixture of 90% (A)and 10% (B)
E) Butyl bromide

Question 22

Which of the following reactions would have an activation energy equal to zero?

A) H-H $\rightarrow$ 2H·
B) H· + CH₃-H $\rightarrow$ CH₃--H + H·
C) CH₃· + CH₃· $\rightarrow$ CH₃-CH₃
D) CH₃· + CH₃-H $\rightarrow$ CH₃-H + CH₃·
E) All of the above

Question 23

Which of the following reactions would have the smallest energy of activation?

A)

B)

C)

D)

E)

Question 24

Which of the following statements is true when used to compare the reaction of fluorine with 2-methylhexane and the reaction of bromine with 2-methylhexane?

A) Bromine is the less reactive and the less selective,giving 2-bromo-2-methyl hexane as one of several products.
B) Fluorine is the less reactive and the more selective,giving 2-fluoro-2-methyl hexane as the major product.
C) Fluorine is the more reactive and less selective,giving 2-fluoro-2-methyl hexane as one of several products.
D) Bromine is the more reactive and the more selective,giving 2-bromo-2-methyl hexane as the major product.
E) More than one of the above statements is true.

Question 25

For which of the following gas-phase reactions would the E_act be equal to $\Delta$ H°?

A) Cl-Cl $\rightarrow$ 2Cl·
B) 2 Cl· $\rightarrow$ Cl-Cl
C) Cl· + CH₄ $\rightarrow$ CH₃· + H-Cl
D) CH₃· + CH₃· $\rightarrow$ CH₃-CH₃
E) CH₃· + Cl-Cl $\rightarrow$ CH₃-Cl + Cl·

Question 26

Which of the following reactions would have an activation energy equal to zero?

A) CH₃-CH₃ -- $\rightarrow$ 2CH₃·
B) H· + CH₃CH₃ -- $\rightarrow$ CH₃CH₃ + H·
C) 2CH₃CH₂· -- $\rightarrow$ CH₃CH₂CH₂CH₃
D) CH₃· + CH₃CH₃ -- $\rightarrow$ CH₃CH₃ + CH₃·
E) None of the above

Question 27

Select the structure of the major product formed in the following reaction.

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

Question 28

What feature would you expect to see in the ¹H NMR spectrum of B after subjecting A to the following reaction?

A) There would be only 4 aromatic protons at low field.
B) The signal for the protons on the benzylic carbon would be a doublet.
C) The signal for the methyl protons would be a triplet.
D) The signal for the methyl protons would be a doublet.
E) The signal for the methyl protons would integrate for only 2 hydrogens.

Question 29

At some temperatures,the relative reactivities of 3°,2° and 1° alkane hydrogens in free radical chlorination are in the ratio of 5:3:1.Thus,monochlorination of isopentane should produce these percentages of 2-chloro-2-methylbutane (A),combined 1-chloro-2-methylbutane and 1-chloro-3-methylbutane (B),and 2-chloro-3-methylbutane (C):

A) 8% A,75% B,17% C
B) 25% A,45% B,30% C
C) 29% A,44% B,18% C
D) 30% A,35% B,35% C
E) 36% A,43% B,21% C

Question 30

Which reaction would you expect to have the smallest energy of activation? $\Delta$ H°(kJ mol^-1)

A) CH₃· + CH₃· -- $\rightarrow$ CH₃CH₃ -378
B) CH₄ + F· -- $\rightarrow$ CH₃· + HF -130
C) CH₄ + I· -- $\rightarrow$ CH₃· + HI +142
D) CH₄ + Br· -- $\rightarrow$ CH₃· + HBr +104
E) CH₄ + Cl· -- $\rightarrow$ CH₃· + HCl +8

Question 31

An example of a reaction having an E_act = 0 would be:

A) Br· + Br-Br -- $\rightarrow$ Br-Br + Br·
B) F· + CH₄ -- $\rightarrow$ H-F + CH₃·
C) CH₃· + Cl· -- $\rightarrow$ CH₃Cl
D) More than one of these
E) None of these

Question 32

What sequence of reactions could be used to prepare cis-1,2-cyclopentanediol from cyclopentane?

A) (1)Cl₂,h $\nu$ ; (2)t-BuOK/t-BuOH; (3)OsO₄; (4)NaHSO₃/H₂O
B) (1)t-BuOK/t-BuOH; (2)Cl₂,h $\nu$ ; (3)NaOH/H₂O
C) (1)Cl₂,h $\nu$ ; (2)t-BuOK/t-BuOH; (3)H₂O₂
D) (1)NaOH/H₂O; (2)Br₂; (3)NaNH₂(2eq. )/liq.NH₃; (4)KMnO₄,NaOH/H₂O,5°C
E) (1)Cl₂,h $\nu$ ; (2)t-BuOK/t-BuOH; (3)Hg(OAc)₂,H₂O (4)NaBH₄,H₃O⁺

Question 33

Which of the following reactions would have the smallest energy of activation?

A) CH₄ + Br· $\rightarrow$ CH₃· + HBr
B) CH₃CH₃ + Br· $\rightarrow$ CH₃CH₂· + HBr
C)

D)

E)

Question 34

An example of a reaction having an E_act = 0 would be:

A) Br· + Br-Br $\rightarrow$ Br-Br + Br·
B) F· + CH₄ $\rightarrow$ H-F + CH₃·
C) CH₃· + CH₃CH₃ $\rightarrow$ CH₄ + CH₃CH₂·
D) Br· + H-Br $\rightarrow$ H-Br + Br·
E) CH₃· + CH₃· $\rightarrow$ CH₃-CH₃

Question 35

Which reaction would you expect to have the largest energy of activation? $\Delta$ H° (kJ mol^-1)

A) CH₃· + CH₃· $\rightarrow$ CH₃CH₃ -378
B) CH₃· + Br· $\rightarrow$ CH₃Br -130
C) CH₄ + I· $\rightarrow$ CH₃· + HI +142
D) CH₄ + Br· $\rightarrow$ CH₃· + HBr +104
E) CH₄ + Cl· $\rightarrow$ CH₃· + HCl +8

Question 36

Mono-bromination of the following alkane, , (using Br₂ with light)would be?

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

Question 37

Which of the following reactions should have the smallest energy of activation?

A) CH₄ + Cl· $\rightarrow$ CH₃· + HCl
B) CH₃CH₃ + Cl· $\rightarrow$ CH₃CH₂· + HCl
C)

D)

E)

Question 38

When an alkane in which all hydrogen atoms are not equivalent is monosubstituted,use of this halogen produces a ratio of isomers which is essentially statistical,i.e. ,dependent only on the number of each type of hydrogen.

A) F₂
B) Cl₂
C) Br₂
D) I₂
E) All of the above

Question 39

Mono-bromination of the following alkane, , (using Br₂ with light)would be?

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

Question 40

Which is true for a chain-terminating step?

A) "A new free radical is formed."
B) "The process is endothermic."
C) "E_act = 0."
D) " $\Delta$ H° is positive."
E) "A product is formed which is immune to further reaction."

Question 41

For which reaction would the transition state be most product-like?

A) CH₄ + Br· $\rightarrow$ CH₃· + HBr
B) CH₃CH₃ + Br· $\rightarrow$ CH₃CH₂· + HBr
C)

D)

E)

Question 42

What is the product for the following three-step reaction sequence?

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

Question 43

Which hydrogen would be abstracted first when mono-brominating with Br₂ and light?

A) Ha
B) Hb
C) Hc
D) Hd
E) He

Question 44

Free radical mono-halogenation of an alkane is typically conducted using bromine versus chlorine because

A) the bromine radical is more reactive and therefore more selective.
B) the chlorine radical is more reactive and therefore more selective.
C) the chlorine radical is less reactive and therefore more selective.
D) the bromine radical is less reactive and therefore more selective.
E) None of the above

Question 45

Mono-bromination of the following alkane, , (using Br₂ with light)would be?

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

Question 46

Mono-bromination of the following alkane, , (using Br₂ with light)would be?

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

Question 47

What is the product for the following three-step reaction sequence?

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

Question 48

Which hydrogen would be abstracted first when mono-brominating with Br₂ and light?

A) Ha
B) Hb
C) Hc
D) Hd
E) He

Question 49

What is the final product,C,obtained via the following reaction sequence?

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

Question 50

Which hydrogen would be abstracted first when mono-brominating with Br₂ and light?

A) Ha
B) Hb
C) Hc
D) Hd
E) He

Question 51

Mono-bromination of the following alkane, , (using Br₂ with light)would be?

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

Question 52

What is the product for the following three-step reaction sequence?

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

Question 53

What is the product for the following three-step reaction sequence?

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

Question 54

What is the product for the following three-step reaction sequence?

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

Question 55

What is the product for the following reaction sequence?

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

Question 56

Which hydrogen would be abstracted first when mono-brominating with Br₂ and light?

A) Ha
B) Hb
C) Hc
D) Hd
E) He

Question 57

Mono-bromination of the following alkane, , (using Br₂ with light)would be?

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

Question 58

What is the product for the following three-step reaction sequence?

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

Question 59

Which hydrogen would be abstracted first when mono-brominating with Br₂ and light?

A) Ha
B) Hb
C) Hc
D) Hd
E) He

Question 60

What is the product for the following three-step reaction sequence?

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

Question 61

The free radical chlorination of pentane produces this number of monochloro compounds,including stereoisomers.

A) 2
B) 3
C) 4
D) 5
E) 6

Question 62

The free radical chlorination of 3-chloropentane forms a mixture of dichloropentanes which,on precise fractional distillation,affords these fractions:

A) 4 fractions,none optically active
B) 4 fractions,2 optically active
C) 7 fractions,4 optically active
D) 7 fractions,6 optically active
E) 7 fractions,all optically active

Question 63

More than one monochloro compound can be obtained from the free radical chlorination of:

A) Cyclopentane
B) Neopentane
C) Isobutane
D) Ethane
E) Methane

Question 64

The p-orbital of a methyl radical carbon,CH₃·,contains how many electrons?

A) 1
B) 2
C) 3
D) 4
E) 0

Question 65

What product would result from the following reaction?

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

Question 66

What is the total number of trichloropropanes which can be produced by free radical chlorination of propane? Include all stereoisomers.

A) 4
B) 5
C) 6
D) 7
E) 8

Question 67

What is the product for the following three-step reaction sequence?

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

Question 68

Free radical chlorination of hexane produces this number of monochloro derivatives (including stereoisomers):

A) 3
B) 4
C) 5
D) 7
E) 8

Question 69

What is the product for the following three-step reaction sequence?

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

Question 70

What is the product for the following three-step reaction sequence?

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

Question 71

How many monochloro derivatives,including stereoisomers,can be formed in the chlorination of 1-bromobutane?

A) 4
B) 5
C) 6
D) 7
E) 8

Question 72

What is the product for the following three-step reaction sequence?

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

Question 73

The reaction of 1-butene with HBr in the presence of peroxides yields 1-bromobutane.The mechanism for the reaction involves:

A) attack on the alkene by a Br⁺ ion.
B) attack on the alkene by a H⁺ ion.
C) attack on the alkene by a bromine atom,Br·.
D) attack on the alkene by a hydrogen atom,H·.
E) isomerization of the 2-bromobutane produced initially.

Question 74

What is the product for the following three-step reaction sequence?

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

Question 75

What is the product for the following three-step reaction sequence?

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

Question 76

Which of the following would serve as the best synthesis of 2-bromohexane?

A)

B)

C)

D)

E) All of the above would be equally suitable.

Question 77

The free radical chlorination of (R)-2-chloropentane forms a mixture of dichloropentanes which includes:

A) three optically active compounds.
B) two achiral compounds.
C) two meso compounds.
D) one pair of diastereomers.
E) one racemic mixture.

Question 78

Consider the light-initiated chlorination of (S)-2-chlorobutane followed by careful fractional distillation (or separation by GLC)of all of the products with the formula C₄H₈Cl₂.How many fractions (in total)would be obtained and how many of these fractions would be optically active?

A) Three fractions total;all optically active
B) Four fractions total;three fractions optically active
C) Five fractions total;all optically active
D) Five fractions total;four fractions optically active
E) Five fractions total;three fractions optically active

Question 79

Free radical chlorination will produce but one monochloro derivative in the case of:

A) Propane
B) Butane
C) Isobutane
D) Isopentane
E) Neopentane

Question 80

Which of the following combinations of reactants can provide a demonstrable example of anti-Markovnikov addition?

A) CH₂=CHCH₃ + HCl + ROOR
B) CH₃CH=CH₂ + H₂O + Cl₂
C) CH₃CH=CHCH₃ + HBr + ROOR
D) CH₃CH₂CH=CH₂ + HBr + ROOR
E) CH₃CH₂CH=CH₂ + Br₂ + ROOR