Ans btopic reaction products section difficulty level medium

1. Free radicals can be produced by:
A) use of high temperatures.

B) irradiation with light.

2. As the term "peroxide" is used in Chapter 10, it can refer to which structure(s)? A) ROOR
B) ROOH

ΔHo=400 kJ/mol ΔHo=243 kJ/mol

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

ΔHo=423 kJ/mol ΔHo=193 kJ/mol

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

ΔHo=421 kJ/mol ΔHo=243 kJ/mol

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

ΔHo=413 kJ/mol ΔHo=159 kJ/mol

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

A) H–H ⎯⎯⎯⎯→ 2H·
B) H· + CH3–H ⎯⎯⎯⎯→ CH3–H + H· C) CH3· + CH3· ⎯⎯⎯⎯→ CH3–CH3
D) CH3· + CH3–H ⎯⎯⎯⎯→ CH3–H + CH3· E) Reactions (B) and (D)

Ans: E

Ans: C

636

CH3CCH2CH3

CH3
D) H

CH3
Ans: C

637

B) C)
	CH3CHCH2CH2
		CH2CHCH2CH3
	CH3

Ans: E

Topic: Reaction Products
Section: 10.3
Difficulty Level: Easy

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

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.

A) Cl–Cl ⎯⎯⎯⎯→ 2Cl·
B) Cl· + CH4⎯⎯⎯⎯→ CH3· + H–Cl
C) CH3· + CH3· ⎯⎯⎯⎯→ CH3–CH3
D) CH3· + Cl–Cl ⎯⎯⎯⎯→ CH3Cl + Cl·
E) More than one of the above
Ans: C

639

H–Cl, ΔH° = 432 kJ mol -1

This mechanism is unlikely because:
A) The overall ΔH° is highly endothermic.

16. Which of the reactions listed below would be exothermic?

A) CH3–CH3⎯⎯⎯⎯→ 2CH3·
B) CH3· + CH4⎯⎯⎯⎯→ CH4 + CH3·
C) 2(CH3)2CH· ⎯⎯⎯⎯→ (CH3)2CH–CH(CH3)2 D) H· + (CH3)3CH ⎯⎯⎯⎯→ (CH3)3CH + H· E) None of the above
Ans: C

B)	Cl					H
C)			Cl		C	H
	δ -							H
	Cl
D)			Cl					H
	Cl				C			H
E)			+	C				H
	δ								H
	Cl
				Cl					H

18. 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)

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

Topic: Reaction Products (Isomers)
Section: 10.3, 10.5
Difficulty Level: Medium

21. 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
Ans: E

Topic: Reaction Products (Isomers)
Section: 10.3, 10.5
Difficulty Level: Medium

A) A new free radical is formed.

B) The process is endothermic.

643

Topic: Activation Energies

Section: 10.5B
Difficulty Level: Easy

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

Ans: C

644

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

Topic: Activation Energies

+ Br . + HBr

C)

. + HBr

E)

30. An example of a reaction having an Eact = 0 would be: A) Br· + Br–Br ⎯⎯⎯⎯→ Br–Br + Br·
B) F· + CH4⎯⎯⎯⎯→ H–F + CH3·
C) CH3· + CH3CH3⎯⎯⎯⎯→ CH4 + CH3CH2· D) Br· + H–Br ⎯⎯⎯⎯→ H–Br + Br·
E) CH3· + CH3· ⎯⎯⎯⎯→ CH3–CH3
Ans: E

646

									+	+	HCl		+	HCl
B) CH3CH3 + Cl· ⎯⎯⎯⎯→ CH3CH2· + HCl
					CH3CHCH2
+			Cl
CH3					CH3					HCl
					CH3CCH3
+			Cl
CH3					CH3
CH3	C	CH3	+		Cl		CH3					CH2
CH3										CH3

ΔH° (kJ mol-1) A) CH3· + CH3· ⎯⎯⎯⎯→ CH3CH3 -378
B) CH3· + Br· ⎯⎯⎯⎯→ CH3Br -130
C) CH4 + I· ⎯⎯⎯⎯→ CH3· + HI +142
D) CH4 + Br· ⎯⎯⎯⎯→ CH3· + HBr +104
E) CH4 + Cl· ⎯⎯⎯⎯→ CH3· + HCl +8
Ans: C

647

Topic: Activation Energies

Section: 10.2, 10.5B
Difficulty Level: Medium

predict which of the following reactions would have the highest energy of activation.

A) CH4 + F· ⎯⎯⎯⎯→ CH3· + HF
B) CH4 + Cl· ⎯⎯⎯⎯→ CH3· + HCl
C) CH4 + Br· ⎯⎯⎯⎯→ CH3· + HBr
D) CH4 + I· ⎯⎯⎯⎯→ CH3· + HI
E) ΔH° values are important, but not sufficient for this prediction Ans: D

Topic: Mechanisms
Section: 10.5C
Difficulty Level: Medium

36. 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?

E) More than one of the above statements is true.

Ans: C

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
Ans: A

heat or light

D) The signal for the methyl protons would be a doublet.

E) The signal for the methyl protons would integrate for only 2 hydrogens.

A) Ethane
B) Propane
C) Butane
D) Isobutane
E) Pentane
Ans: D

Topic: Reaction Products
Section: 6.18, 8.16, 10.6
Difficulty Level: Hard

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

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

Topic: Reaction Products
Section: 10.6A
Difficulty Level: Easy

Topic: Reaction Products
Section: 10.6A
Difficulty Level: Easy

45.	Mono-bromination of the following alkane,		, (using Br2 with light)

B) II
C) III
D) IV
E) V
Ans: A

653

Br

Br

Br Br Br

Topic: Reaction Products
Section: 10.6A
Difficulty Level: Easy

48.

Topic: Reaction Products
Section: 10.6A
Difficulty Level: Easy

be?

Topic: Reaction Products
Section: 10.6A
Difficulty Level: Medium

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

Topic: Reaction Products
Section: 10.6A
Difficulty Level: Medium

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

Topic: Reaction Products
Section: 10.6A
Difficulty Level: Medium

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

Topic: Reaction Products
Section: 10.6A
Difficulty Level: Medium

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

Topic: Reaction Products
Section: 10.6A
Difficulty Level: Medium

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

56. Free radical fluorination of an alkane is not typically conducted because of fluorine’s high reactivity due to
A) the low energy of activation for the chain-propagating steps.

B) the large negative overall ΔHo for the reaction.

Topic: Reaction Products
Section: 10.6A
Difficulty Level: Medium

57. Free radical iodination of an alkane is not feasible because
A) the iodine-iodine bond is relatively weak compared to the other halogens. B) the overall ΔHo for the reaction is favorable.

B) The transition state of the rate determining step is product-like.

C) The major product formed from this reaction is 1-bromo-2-methylpropane.

B) II
C) III
D) IV
E) V
Ans: C

		1. Br2, hν	O
		2. CH3CH2OH, heat
I	II	III	IV	V

Topic: Reaction Products
Section: 6.18, 10.6A
Difficulty Level: Medium

62. What would be the major product of the following reaction sequence?

		OH		Ot-Bu
I	II	III	IV	V
A) I

B) II
C) III
D) IV
E) V
Ans: C

Topic: Reaction Products
Section: 6.18, 10.6A
Difficulty Level: Medium

		2. EtOH, EtONa, heat
		O
I	II	III		IV	V

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

		1. Br2, hν			SCH3
	DMF
	Ph
I	II			V
		III	IV

1. Br2, hν

Topic: Reaction Products
Section: 6.18, 10.6A
Difficulty Level: Hard

					OEt
		2. EtOH, EtONa, heat
	OH Ph
I	II			V
		III	IV

Br Br
		2. H2, Pd/C 3. Br2, hν
	Br
				Br
I	II	III	IV
				V

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

665

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

		3a. Hg(OAc)2, H2O
			O
I	II	III	IV	V

Topic: Multistep Reactions
Section: 6.18, 8.7, 10.6A
Difficulty Level: Hard

Br2	A			B	ii) H2O2, OH−
hν
	heat
OH			OH			OH OH
I	II	III			IV

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

Topic: Synthesis
Section: 6.18, 8.12, 10.6A
Difficulty Level: Hard

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

	Cl			Cl	OH	Cl
I		II		III	IV		V

Topic: Synthesis
Section: 6.18, 8.16, 10.6A
Difficulty Level: Hard

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

670

		OH	1. Br2, hν			OH
			OH
			CO2H
			CO2H
I	II		III	IV	V

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

Topic: Synthesis
Section: 6.18, 8.17, 10.6A
Difficulty Level: Hard
80. What is the product for the following three-step reaction sequence?

CHO CHO				OH	OH
			O
I	II		III	IV	V

	CHO CHO	OH	OH	OCH3
O
I	II	III		IV	V

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

Topic: Free Radicals
Section: 10.7
Difficulty Level: Easy

672

Topic: Free Radicals
Section: 10.7
Difficulty Level: Easy

Topic: Reaction Products (Isomers)
Section: 10.3, 10.5, 10.8
Difficulty Level: Medium

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

Topic: Reaction Products (Isomers)
Section: 10.3, 10.5, 10.8
Difficulty Level: Medium

87. Free radical chlorination of hexane produces this number of monochloro derivatives (including stereoisomers):
A) 3
B) 4
C) 5
D) 7
E) 8
Ans: C

89. 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
Ans: C

E) one racemic mixture.

Ans: B

Topic: Reaction Products (Isomers)
Section: 10.3, 10.5, 10.8
Difficulty Level: Hard

92. 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
Ans: A

Topic: Reaction Products
Section: 10.9
Difficulty Level: Easy

94. What would be the major product of the following reaction?

					?
			CH3 OR
I		II	Br			V
			III	IV

96. 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.

Ans: C

Topic: Synthesis
Section: 10.9
Difficulty Level: Medium

Topic: Reaction Products
Section: 10.9
Difficulty Level: Medium

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

99. 2-Methyl-2-butene reacts with HBr in the presence of peroxide to give (chiefly): A) (CH3)2CHCH2CH2Br
B) (CH3)2CHCHCH3

Topic: Reaction Products
Section: 6.5, 10.9
Difficulty Level: Medium

100. What would be the major product of the following reaction sequence?

Topic: Reaction Products
Section: 6.5, 10.9
Difficulty Level: Medium

101. What would be the major product of the following reaction sequence?

		1. HBr, ROOR, hν
	NC
CN
I	II	III	IV		V

1. HBr, ROOR, hν

2. CH3CH2OH

B) II
C) III
D) IV
E) V
Ans: A

680

Ot-Bu				Ot-Bu
		2. t-BuOK, t-BuOH, heat
I	II	III	IV	V

B) II
C) III
D) IV
E) V
Ans: B

681

	2. t-BuOK, t-BuOH, heat

3. HBr, ROOR, hν

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

	2. t-BuOK, t-BuOH, heat

3. HBr, ROOR, hν

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

1. HBr, ROOR, hν

2. t-BuOK, t-BuOH, heat

			OEt		OH
I		II	III	IV	V

Topic: Reaction Products
Section: 6.18, 10.9
Difficulty Level: Medium

108. What would be the major product of the following reaction sequence?

Br	Br Br
I	II	III	IV	V
A) I

B) II
C) III
D) IV
E) V
Ans: C

110. What would be the major product of the following reaction sequence?

Br	Cl	Br
					Br
			Br	Br
					+

diastereomer

111. What would be the major product of the following reaction sequence?

Br	Cl	Br
					Br
			Br	Br
					+

diastereomer

					OCH3
	OH
I	II			V
		III	IV

B) II
C) III
D) IV
E) V
Ans: A

685

114. Which would be the best way to carry out the following synthesis? ?

(CH3)3COH (CH3)2CHCH2Br

NC				1. Li, NH3
		NC
	I	II		III	IV	V

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

117. What is the major product obtained from the following reaction sequence?

HBr peroxides A t-BuOK t-BuOH B

OH

688

		1. HBr, ROOR, hν		I I
I	II	III	IV	V

NaSH D hν t-BuOH peroxides
heat

SH SH SH

Topic: Multistep Reactions
Section: 6.5, 6.18, 10.6A, 10.9
Difficulty Level: Hard

120. What is the major product obtained from the following reaction sequence?

121. If propene polymerization is initiated by the use of diacyl peroxide, this is an intermediate species formed early in the process.

690

Topic: Miscellaneous
Section: 10.11D
Difficulty Level: Medium

123. Intermediates possessing unpaired electrons are called ______________. Ans: radicals or free radicals

Topic: General
Section: 10.1
Difficulty Level: Easy

691

Topic: General
Section: 10.2B
Difficulty Level: Medium

Topic: General
Section: 10.4
Difficulty Level: Easy

128. In a chain-initiating step, radicals are _____________. Ans: created or formed

692

Ans: The energy of activation for the first propagation step in the free radical
mechanism for halogenation of alkanes determines the overall reactivity pattern for the various halogens. In contrast to the reaction with the other halogens, hydrogen atom abstraction from an alkane by an iodine atom has a very high energy of activation- since this is the first propagation step, the overall process is affected as well and iodination does not occur to any appreciable extent.

I . + R-H à H-I + R .

133. Briefly, but clearly, explain the following observation:
When 2-methylbutane reacts with Cl2/hν, the monochlorinated products consist of four constitutional isomers in significant yields. However, when the same alkane is allowed to react with Br2/ hν, there is only one major monobromination product.

Ans: The final product distribution is a consequence of the relative ease of hydrogen atom abstraction from primary, secondary and tertiary positions. Chlorine is highly reactive and therefore there is not much differentiation between the different kinds of hydrogen atoms- as a result, all the possible free radicals are formed, leading to the formation of all possible constitutional isomers. Bromine is less reactive and more selective than chlorine in its reaction with alkanes; this results in the selective abstraction of the tertiary hydrogen atom at C2, to give the most stable radical intermediate, a tertiary radical, leading to the selective formation of only one major monobromination product.

		Cl	Cl

694

Ans:		+	hν					BH2 H
	H3C H			heat		BH3, THF
						H3C H	+

136. Draw bond-line formulas of all monochloro derivatives that might be formed when 2,3-dimethylbutane is allowed to react with Cl2 under UV irradiation. For each structure, indicate, with an asterisk, any stereocenters that might be present.

Ans:		Cl2, hν	Cl
			Cl	*	+

Topic: Reaction Products (Isomers)
Section: 10.6, 10.8
Difficulty Level: Medium

137. Draw bond-line formulas of all monochloro derivatives that might be formed when 1,1-dimethylcyclobutane is allowed to react with Cl2 under UV irradiation. For each structure, indicate, with an asterisk, any stereocenters that might be present.

1,1-dimethylcyclobutane Topic: Reaction Products (Isomers) Section: 10.6, 10.8
Difficulty Level: Medium

Ans: Cl

140. Draw bond-line formulas of all dichloro derivatives that might be formed when 1-chloro-2,2,3,3,-tetramethylpentane is allowed to react with Cl2 under UV irradiation. For each structure, indicate, with an asterisk, any stereocenters that might be present.

dichloro derivatives

Topic: Reaction Products (Isomers)
Section: 10.6, 10.8
Difficulty Level: Medium

monochloro derivatives

Ans: radical or free-radical; anti-Markovnikov

Topic: General
Section: 10.9
Difficulty Level: Medium

Ans: The addition of HBr to 2-methylpropene takes place via the formation of the most stable free radical intermediate, by addition of a bromine atom at C1. Two such radicals can couple together via a termination step to afford 1,4-dibromo-2,2,3,3-tetramethylbutane as a minor product. Analogous coupling between this radical and a bromine radical leads to the formation of 1,2-dibromo-2-methylpropane as another minor product.

						Br
	peroxides
	Br	+				Br			Br
	Br+		Br

termination steps: radical coupling

698

heat

iv) NaCN

Topic: General
Section: 10.10
Difficulty Level: Easy

147. Macromolecules made up of many repeating subunits are called ____________. Ans: polymers

Topic: General
Section: 10.11D
Difficulty Level: Easy

149. Chlorofluorocarbons, or freons, diffuse into the upper atmosphere. There, ultraviolet light initiates a radical chain reaction that has been shown to cause extreme damage to _______________.