Deck 3: Reactions of Alkanes: Bond-Dissociation Energies,radical Halogenation,and Relative Reactivity

Question 1

What is the major product of the following reaction?

A)

B)

C)

D)

E) no reaction occurs

Answer 1

Question 2

Hyperconjugation is most useful for stabilizing which of the following?

A) neopentyl radical
B) tert-butyl radical
C) isopropyl radical
D) ethyl radical
E) methyl radical

Answer 2

tert-butyl radical

Question 3

The order of radical stability is:

A) 3° > 2° > 1° > Me
B) 3° < 2° < 1° < Me
C) all are about equal in stability
D) Me > primary
E) tertiary and methyl are equal in stability

Answer 3

3° > 2° > 1° > Me

Question 4

Which of the following reaction types are typical of alkanes?

A) addition
B) elimination
C) radical substitution
D) reduction
E) more than one of these is correct

Question 5

Which of the following is a propagation step in the free-radical bromination of methane?

A)

B)

C)

D)

E)

Question 6

Which of the reactions below would you expect to have the largest positive $\Delta$ ?

A)

B)

C)

D)

E)

Question 7

Predict the major product of the following reaction:

A)

B)

C)

D)

E) no reaction

Question 8

Free-radical fluorination demonstrates little regio-selectivity because

A) fluorine is too small to have steric hinderance.
B) free-radical reactions are never regio-selective.
C) a late transition state is involved.
D) an early transition state is involved.
E) fluorine is too unreactive.

Question 9

Alkanes are noted for their (choose one)

A) high reactivity with acids.
B) toxicity.
C) intense odor.
D) lack of reactivity.
E) water-solubility.

Question 10

Which of the following is true for an early transition state?

A) The starting materials resemble the products.
B) The reaction proceeds very slowly.
C) The transition state resembles the reactants.
D) The transition state resembles the products.
E) both B and C

Question 11

Predict the major monofluorination product from the following reaction:

A)

B)

C)

D)

E)

Question 12

Which,if any,of the following would you choose to accomplish the reaction shown below in the best yield?

A) F₂,light
B) Cl₂,light
C) Br₂,light
D) I₂,light
E) None of the above.

Question 13

In a carbon radical,the carbon possesses how many valence electrons?

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

Question 14

Which of the carbon-carbon bonds indicated would be the weakest?

A) A
B) B
C) C
D) D
E) E

Question 15

Predict the major product of the following reaction:

A)

B)

C)

D)

E)

Question 16

Given the relative reactivities of various kinds of hydrogens,the major product expected from mono-bromination of 2-methylbutane would be what?

A)

B)

C)

D)

E)

Question 17

What reactant is needed to complete and balance the following reaction?

A) C₃H₈
B) C₂H₆
C) C₃H₄
D) C₃H₆
E) C₆H₁₂

Question 18

In a carbon radical,the single unpaired electron resides in:

A) sp² orbital
B) sp³ orbital
C) s orbital
D) p orbital
E) None of the above.

Question 19

Which one of the reactions below will not proceed and accounts for why iodine added to a free-radical chlorination or bromination will greatly slow or even stop the reaction?

A)

B)

C)

D)

E)

Question 20

Which of the following is not true of free-radical halogenation reactions?

A) Fluorine is more reactive than chlorine in these reactions.
B) Bromine is more selective than chlorine.
C) The reactions require either light or high temperatures to proceed.
D) Brominations are faster than chlorinations.
E) These reactions are irreversible.

Question 21

Carbon dioxide is an essential greenhouse gas that insulates the planet and maintains a surface temperature that allows life to flourish.Human activities have resulted in a dramatic increase in the greenhouse gases in the atmosphere.Which of the following reactions produce the most carbon dioxide per mole of carbon-containing starting material? (Note that these equations are not balanced.)

A)

B)

C)

D) All produce the same amount of carbon dioxide.
E) None of these reactions produce carbon dioxide.

Question 22

Which of the following would you not expect to be formed in even small amounts during the free-radical chlorination of methane?

A) CH₂Cl₂
B) CH₃CH₃
C) CHCl₃
D) CCl₄
E) Some of all of these would be formed.

Question 23

Rank the following radicals in decreasing order of stability.

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

Question 24

How many constitutional isomers can be formed from the monochlorination of the hydrocarbon shown below?

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

Question 25

Which of the following hydrocarbons would yield only a single mono-chloro derivative under free radical chlorination conditions? (Cl₂/h $\nu$ )

A)

B)

C)

D)

E)

Question 26

What reactant is needed to complete and balance the following reaction?

A) C₃H₈
B) C₂H₆
C) C₃H₄
D) C₃H₆
E) C₆H₁₂

Question 27

Chemists have determined that chlorofluorocarbons are contributing to destruction of the protective ozone layer.Upon irradiation of chlorofluorcarbons,chlorine radicals are produced and react with the ozone via the chemical process shown below.Which of the following statement(s)are true based upon these equations?

A) Termination steps in the equations above are contributing to ozone depletion.
B) A single chlorine radical is capable of destroying many molecules of ozone since it is regenerated.
C) Chlorine radicals are the result of a heterolytic cleavage of the C-Cl bond of the chlorofluorocarbon.
D) A,B and C are correct.
E) B and C are correct.

Question 28

Which is most true about the function of a catalyst?

A) Catalysts speed up the reaction by lowering the transition state of a reaction.
B) Catalysts usually need higher temperatures to promote reactions.
C) Catalysts lower the energies of the reactants.
D) Catalysts lower the energies of the products.
E) Catalysts increase the yield of the reaction.

Question 29

Which alkane below would you expect to have the lowest heat of combustion?

A)

B)

C)

D)

E) All would be the same.

Question 30

Given the relative reactivities of various kinds of hydrogens,the major product expected from mono-chlorination of 2-methylbutane would be what?

A)

B)

C)

D)

E) There is no way to predict this.

Question 31

How many different products will result if radical monobromination of the following compound only occurs at 3° carbons.

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

Question 32

Give the relative reactivity in decreasing order for free radical halogenation of (CH₃)₃CH.

A) F > Cl >Br
B) Cl > Br > F
C) Br > F > Cl
D) Br > Cl > F
E) I > F > Cl

Question 33

The following reaction represents what type of process?

A) Propagation
B) Termination
C) Initiation
D) Nucleophilic addition
E) None of the above.

Question 34

In a free radical termination step:

A) an initiator starts a chain reaction.
B) free radicals recombine with one another.
C) a radical reacts to form another radical.
D) the activation energy is high.
E) a reactive intermediate is formed.