Complete Test Bank Radical Reactions Ch.13

Organic Chemistry, 6e (Smith)

Chapter 13 Radical Reactions

1) Which of the following statements about radicals and radical reactions is not true?

A) Most radicals are unstable.

B) A radical contains an atom that has an octet of electrons.

C) Half-headed arrows are used to show the movement of lone electrons.

D) A radical is formed by homolysis of a covalent bond.

2) Which of the following statements about carbon radicals is not true?

A) Carbon radicals are classified as primary, secondary, tertiary, or quaternary.

B) A carbon radical is sp2 hybridized.

C) The geometry of a carbon radical is trigonal planar.

D) The unhybridized p orbital in a carbon radical contains the unpaired electron.

3) Which of the following statements about radicals is true?

A) Cleavage of a stronger bond forms the more stable radical.

B) The stability of a radical increases as the number of alkyl groups bonded to the radical carbon decreases.

C) The higher the bond dissociation energy for a C-H bond, the more stable the resulting carbon radical.

D) Less stable radicals generally do not rearrange to more stable radicals.

4) Which of the following compounds contain primary (1°) radical carbons?

A) Only I

B) Only II

C) Only III

D) Only II and IV

5) Which of the following compounds contain secondary (2°) radical carbons?

A) Only I

B) Only II

C) Only III

D) Only II and IV

6) Which of the following compounds contain tertiary (3°) radical carbons?

A) Only I

B) Only II

C) Only III

D) Only II and IV

7) Which of the following is a radical scavenger?

A) O3

B) O2

C) Vitamin C

D) CO2

8) How many monochlorination products can be formed (constitutional isomers only) from the reaction of (CH3)2CHCH2CH3 with Cl2 and hn?

A) 2

B) 3

C) 4

D) 5

9) How many monochlorination products can be formed (constitutional isomers only) from the reaction of CH3CH2CH2CH2CH2CH3 with Cl2 and hn?

A) 3

B) 4

C) 5

D) 6

10) How many monochlorination products can be formed from the reaction of (CH3)3CH with Cl2 and hn?

A) 1

B) 2

C) 3

D) 4

11) Which of the following statements about radical reactions is not true?

A) Light or heat provides the energy needed for homolytic bond cleavage to form radicals.

B) Breaking the weak O-O bond of peroxides initiates radical reactions.

C) The diradical O2 removes radicals from a reaction mixture.

D) Radicals rearrange.

12) Which steps are the rate-determining step in the mechanism of radical halogenation?

A) Initiation

B) Propagation

C) Termination

D) Initiation and propagation

13) Which of the following statements about the propagation steps in the chlorination of ethane is true?

A) Radical chlorination consists of two propagation steps.

B) The energy diagram for the propagation steps has three energy barriers.

C) The first of the propagation steps is rate-determining because its transition state is at lower energy.

D) The second of the propagation steps is rate-determining because its transition state is at higher energy.

14) Which of the following statements about chlorination and bromination is true?

A) Bromination is unselective, yielding a mixture of products.

B) Chlorination is often selective, yielding one major product.

C) Chlorination is faster than bromination.

D) Bromination is faster than chlorination.

15) Which of the following statements about bromination is true?

A) The rate-determining step in bromination is exothermic.

B) Both radicals are formed.

C) A mixture of products results.

D) A single radical halogenation product predominates.

16) Which of the following statements about chlorination is true?

A) The rate-determining step in chlorination is endothermic.

B) The transition state resembles the product.

C) The more stable radical is formed faster.

D) A mixture of products results.

17) What is the product in the following sequence of reactions?

A) I

B) II

C) III

D) IV

18) What is the product in the following sequence of reactions?

A) I

B) II

C) III

D) IV

19) Which of the following statements about the stereochemistry of halogenation reactions is true?

A) An achiral starting material always gives an achiral product only.

B) An achiral starting material always gives a racemic product only.

C) The configuration at a stereogenic center of a product must change even if a reaction does not occur at a stereogenic center.

D) An achiral starting material always gives either an achiral or a racemic product.

20) How many monochlorination products (constitutional isomers and stereoisomers) are formed from the reaction of butane with Cl2 and hn?

A) 2

B) 3

C) 4

D) 5

21) How many monochlorination products (constitutional isomers and stereoisomers) are formed from the reaction of pentane with Cl2 and hn?

A) 2

B) 3

C) 4

D) 5

22) Rank the following radicals in order of increasing stability, putting the least stable first.

A) III< I < II

B) I < II < III

C) III < II < I

D) I < III < II

23) Rank the following radicals in order of decreasing stability, putting the most stable first.

A) II > IV > III > I

B) III > II > IV > I

C) IV > III > II > I

D) IV > III > I > II

24) What is the product of the following reaction?

A) I

B) II

C) III

D) IV

25) What is the product of the following reaction?

A) I

B) II

C) III

D) IV

26) How many allylic halides can be formed when 3-methycyclohexene undergoes allylic halogenation with one equivalent of NBS and light?

A) 1

B) 2

C) 3

D) 4

27) What is the product of the following reaction?

A) I

B) II

C) III

D) IV

28) Identify the monomer used to make the following polymer.

A) I

B) II

C) III

D) IV

29) Identify the monomer used to make the following polymer.

A) I

B) II

C) III

D) IV

30) Identify the monomer used to make the following polymer.

A) I

B) II

C) III

D) IV

31) Determine the monochlorination product(s).

A) Only I

B) Only II

C) Only III

D) Only I and II

32) Determine the product of the following reaction.

A) I

B) II

C) III

D) IV

33) Determine the product(s) of the following reaction.

A) Only I

B) Only II

C) Only III

D) Only I and II

34) Which of the following statements is (are) true about free radical halogenation of alkanes?

A) The first of the chain-propagating steps is rate-determining.

B) The reaction proceeds by way of a flat sp2 hybridized free radical.

C) The chain-initiating step involves cleavage of a carbon-hydrogen bond to afford a carbon radical and a hydrogen atom.

D) Statements (The first of the chain-propagating steps is rate-determining) and (The reaction proceeds by way of a flat sp2 hybridized free radical) are both true.

35) Which of the labeled hydrogens is most easily abstracted in a free radical bromination reaction?

A) Ha

B) Hb

C) Hc

D) Hd

36) Which of the indicated hydrogens is most readily abstracted in a free radical halogenation reaction?

A) I

B) II

C) III

D) IV

37) A possible reaction of ethane with chlorine is shown below.

This reaction could conceivably occur by the following chain mechanisms [1], [2], and [3]. The chain initiating step(s) is (are) ________.

A) Only [1]

B) Only [2]

C) Only [3]

D) Only [1] and [2]

38) A possible reaction of ethane with chlorine is shown below.

This reaction could conceivably occur by the following chain mechanisms [1], [2], and [3]. The chain propagating step(s) is (are) ________.

A) Only [1] and [2]

B) Only [2] and [3]

C) Only [1] and [3]

D) Only [3]

39) A possible reaction of ethane with chlorine is shown below.

This reaction could conceivably occur by the following chain mechanisms [1], [2], and [3]. Determine DH for step [1].

Bond dissociation energies (kcal/mol):

A) -5 kcal/mol

B) +58 kcal/mol

C) -28 kcal/mol

D) None of the choices are correct.

40) A possible reaction of ethane with chlorine is shown below.

This reaction could conceivably occur by the following chain mechanisms [1], [2], and [3]. Determine DH for step [2].

Bond dissociation energies (kcal/mol):

A) -5 kcal/mol

B) +58 kcal/mol

C) -28 kcal/mol

D) None of the choices are correct.

41) Select the route that would most likely produce the desired results from the given starting material.

I.(1) H2SO4 and heat; (2) HBr

II.(1) KOH in ethanol; (2) HBr

III.(1) H2SO4 and heat; (2) HBr + peroxides

IV.(1) potassium tert-butoxide in tert-butanol; (2) HBr + peroxides

A) I

B) II

C) III

D) IV

42) What type of reactive intermediate is formed in the reaction of propene with N-bromosuccinimide (NBS) to give 3-bromo-1-propene?

A) Cyclic bromonium ion

B) Allylic carbocation

C) Allylic carbanion

D) Allylic radical

43) Which of the following alkenes undergoes allylic bromination to form a single monobrominated product?

A) I

B) II

C) III

D) IV

44) How many monochlorination products, including stereoisomers, are formed from (S,S)-1,2-dimethylcyclopropane?

A) 4

B) 3

C) 6

D) 5

45) How many products, including stereoisomers, are formed when 2-methylpent-2-ene is treated with HBr in presence of peroxides?

A) 1

B) 2

C) 3

D) 4

46) How many products, including stereoisomers, are formed when (R)-2,4-dimethylhex-2-ene is treated with HBr in presence of peroxides?

A) 1

B) 2

C) 3

D) 4

47) Rank the following in order of increasing stability.

A) I < II < III < IV

B) II < I < III < IV

C) I < II < IV < III

D) IV < III < II < I

48) What is/are the product(s) of the following monochlorination?

A) I

B) II

C) III

D) All of the choices are correct.

49) For a radical reaction, put the following steps in the correct order:

1. Initiation

2. Propagation

3. Termination

A) 1, 2, 3

B) 1, 3, 2

C) 2, 3, 1

D) 3, 2, 1

50) Which of the following would be the fastest to form a radical?

A) I

B) II

C) III

D) IV

51) Find the major product of the following reaction.

A) I

B) II

C) III

D) IV