Deck 7: Delocalized Electrons Aromaticity and the Reactions of Benzene

Question 1

Which of the following is a benzylic cation? I.


II.


III.


IV.


V.

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

Answer 1

IV

Question 2

Which of the following does not have delocalized electrons?

A) allyl cation
B) benzyl anion
C) CO₃^2-
D) benzyl cation
E) cyclohexyl radical

Answer 2

cyclohexyl radical

Question 3

What type of diene is represented by 1,5-octadiene?

A) conjugated diene
B) isolated diene
C) alkynyl diene
D) none of the above

Answer 3

isolated diene

Question 4

Which has correctly drawn arrows?

A)
B)
C)
D)
E)

Question 5

What type of diene is represented by 2,4-hexadiene?

A) conjugated diene
B) isolated diene
C) alkynyl diene
D) none of the above

Question 6

Which of the following statements is not correct about benzene?

A) All of the carbon atoms are sp hybridized.
B) It has delocalized electrons.
C) The carbon-carbon bonds are all the same length.
D) The carbon-hydrogen bonds are all the same length.
E) All twelve atoms lie in the same plane.

Question 7

Which of the following is an allylic cation? I.


II.


III.


IV.


V.

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

Question 8

Which of the following compounds has the shortest bond between its two middle carbons?

A)
B)
C)
D)
E)

Question 9

Which of the following is the most stable?

A) $\mathrm { CH } _ { 2 } = \mathrm { CH } - \mathrm { OCH } _ { 3 }$
B) $\mathrm { CH } _ { 2 } - \mathrm { CH } = \mathrm { OCH } _ { 3 }$
C)
D)
E)

Question 10

Which of the following pairs are resonance contributors? I. $\mathrm { CH } _ { 2 } = \mathrm { CHCH } _ { 3 }$ and

II.


III.


IV.


V.

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

Question 11

Which of the following is the most stable carbocation? I. $\mathrm{CH}_{3}{ }\mathrm{C}^{\oplus} =\mathrm{CH}_{2}$

II.


III.


IV.


V.

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

Question 12

Which of the following statements about resonance contributors and resonance hybrids is not correct?

A) The fewer nearly equivalent resonance contributors, the greater the resonance energy.
B) A resonance hybrid is more stable than the predicted stability of any of its resonance contributors.
C) The greater the number of relatively stable resonance contributors, the greater the resonance energy.
D) The greater the predicted stability of a resonance contributor, the more it contributes to the resonance hybrid.
E) none of the above

Question 13

Which of the following statements about benzene is correct?

A) All of the carbon atoms are sp³ hybridized.
B) It has no delocalized electrons.
C) The carbon-carbon bonds are longer than the carbon-carbon bond in ethane.
D) It is a planar molecule.
E) The carbon-hydrogen bonds are not the same length.

Question 14

Which of the following is the most stable diene? I.


II.


III.


IV.


V.

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

Question 15

Which of the following pairs are resonance contributors? I.



II.


III.

IV.

V.

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

Question 16

Which of the following is a resonance hybrid?

A)
B)
C)
D)
E) A,B, and C.

Question 17

Which of the following is not a resonance contributor of the species shown below?

I.


II.


III.


IV.

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

Question 18

Which of the following compounds contains the longest carbon-carbon single bond?

A) propene
B) 1,3-butadiyne
C) 1,3-butadiene
D) propyne
E) ethane

Question 19

Due to electron delocalization, one would predict that the carbon-oxygen bond in CH₃CONH₂.

A) is nonpolar
B) has more double bond character than the carbon-oxygen bond of (CH₃)₂CO
C) is longer than the carbon-oxygen bond of (CH₃)₂O
D) is longer than the carbon-oxygen bond of (CH₃)₂CO
E) is formed by overlapping sp³ orbitals

Question 20

The delocalized cloud of π electrons in benzene is formed by the overlap of 6 ________ orbitals.

A) s
B) p
C) sp
D) sp²
E) sp³

Question 21

What are the major products of the following reaction?
$\mathrm { CH } _ { 2 } = \mathrm { CH } - \mathrm { CH } = \mathrm { CH } _ { 2 } \stackrel { \mathrm { HBr } } { \longrightarrow } \text { ? }$

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

Question 22

What are the major products of the following reaction?

$\mathrm { CH } _ { 3 } \mathrm { CH } = \mathrm { CHCH } = \mathrm { CHCH } _ { 3 } \stackrel { \mathrm { HBr } } { \longrightarrow }$

A)
B)
C)
D)
E)

Question 23

What are the major products of the following reaction?

A) I
B) II
C) I and II with more II and I
D) neither I nor II
E) equal amounts of I and II

Question 24

What is the major product of the following reaction?

A)

B)

C)

D)

E)

Question 25

What is the major product of the following reaction?

A)
B) $\mathrm { BrCH } _ { 2 } \mathrm { CH } _ { 2 } \mathrm { CH } _ { 2 } \mathrm { CH } _ { 2 } \mathrm { CH } = \mathrm { CH } _ { 2 }$
C)
D) $\mathrm { BrCH } _ { 2 } \mathrm { CH } _ { 2 } \mathrm { CH } _ { 2 } \mathrm { CH } _ { 2 } \mathrm { CH } _ { 2 } \mathrm { CH } _ { 2 } \mathrm { Br }$
E)

Question 26

What is the major product of the following reaction?

A)
B)
C)
D)
E) no reaction

Question 27

What is the major product of the following reaction?

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

Question 28

Draw the major product of the following reaction.

I.
II.
II.

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

Question 29

Which of the following is the strongest acid? I.


II.


III.


IV.


V.

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

Question 30

Which is the most stable carbocation?

A)
B)
C)
D)
E)

Question 31

What are the major products of the following reaction? $$\mathrm { CH } _ { 2 } = \mathrm { CHCH } = \mathrm { CH } _ { 2 } + \mathrm { HBr } \longrightarrow \text { ? }$$
I.


II.


III.

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

Question 32

What compound results from the 1,4-addition of one equivalent of HBr to 1,3-butadiene?

A) 1-bromo-1-butene
B) 2-bromo-2-butene
C) 4-bromo-1-butene
D) 3-bromo-1-butene
E) 1-bromo-2-butene

Question 33

What is the major product of the following reaction?

I.

II.

III.

IV.

V.

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

Question 34

What is the major product of the following reaction?

A)
B)
C)
D)
E)

Question 35

Which of the following ammonium ions is the strongest acid?

A)C₆H₅NH₃⁺
B)C₆H₅CH₂NH₃⁺
C) (CH₃)₂CHNH₃⁺
D)CH₃CH₂NH₃⁺
E)CH₃NH₃⁺

Question 36

When 1,3-butadiene reacts with CH₂ = CHCN , which of the following terms describes the product?

A) a mixture of two diastereomers
B) a single compound
C) a racemic mixture
D) optically active
E) a mixture of bicyclic compounds

Question 37

Which of the following is the weakest base?

A) phenolate ion (C₆H₅O-)
B) ethoxide ion (CH₃CH₂O-)
C) hydroxide ion (HO^-)
D) acetate ion (CH₃CO₂-)
E) methoxide ion (CH₃O-)

Question 38

Which of the following is a conjugated diene? I.


II.


III.


IV.


V.

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

Question 39

Which of the following is the strongest acid?

A) $\mathrm { CH } _ { 3 } \mathrm { CH } _ { 2 } \mathrm { OH }$
B) $\mathrm { CH } _ { 3 } \mathrm { OCH } _ { 3 }$
C)
D)
E)

Question 40

Which of the following is an isolated diene? I.


II.


III.
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IV.


V.

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

Question 41

Do the following represent different compounds or resonance contributors?

Question 42

Aromatic molecules contain ________ π electrons.

A) no
B) an odd number of pairs of
C) an even number of pairs of
D) an odd number of
E) an even number of

Question 43

Which of the oxygens in the acetate ion (CH₃CO₂^-) has a greater negative charge? Explain
your answer.

Question 44

Draw the resonance contributors for the following species:

Question 45

Which of the following is aromatic? I.

II.

III.

IV.

V.

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

Question 46

Draw the other two resonance contributors for the following species:

Question 47

Draw the other two resonance contributors for the following species:

Question 48

What is the hybridization and bond angle of each carbon in benzene?

Question 49

What is the hybridization of the carbons labeled A, B, and C?

Question 50

Draw the other two resonance contributors for the following species:

Question 51

Draw the resonance contributors for the following species:

Question 52

Which of the following is an aromatic hydrocarbon? I.

II.

III.

IV.

V.

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

Question 53

Draw the other two resonance contributors for the following species:

Question 54

Mark the most electron-rich carbon in the compound below with an asterisk. CH₃CH=CHNHCH₃

Question 55

Draw the other two resonance contributors for the following species:

Question 56

Which of the following is aromatic?

A) the cyclopentadienyl cation
B) 1,3-cyclohexadiene
C) the cyclobutenyl anion
D) 1,3,5-hexatriene
E) the cycloheptatrienyl cation

Question 57

Draw the other two resonance contributors for the following species:

Question 58

Which of the following is aromatic? I.

II.

III.

IV.

V.

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

Question 59

Which of the following is aromatic?

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

Question 60

Draw the resonance contributor for the following carbocation:

Question 61

What is the major product of the following reaction?

Question 62

Which of the following is the strongest acid?

Question 63

Draw the major product of the following reaction:

Question 64

Why is the following compoound not aromatic?

Question 65

Draw the major product of the following reaction:

Question 66

Draw the arrows to go from one resonance contributor to another.

Question 67

Draw the major product of the following reaction:

Question 68

What is the product of the following Diels-Alder reaction?

Question 69

List the criteria that compounds must meet in order to be aromatic.

Question 70

Which of the following carbocations is more stable? Explain.

Question 71

Is the following molecule aromatic? Explain.

Question 72

What is the major product of the following reaction?

Question 73

Draw the major product of the following reaction:

Question 74

Why is benzene's heat of hydrogenation 36 kcal/mol less than three times that of cyclohexene?

Question 75

What diene and dienophile will react to form the product shown below?

Question 76

How could the following compound be synthesized using a Diels-Alder reaction?

Question 77

Why is phenol a stronger acid than cyclohexanol?

Question 78

Draw the product that is formed from 1,4-addition of HBr to the following diene:

Question 79

Draw the resonance contributors for the following species:

Question 80

Draw the product that is formed from 1,2-addition of HBr to the following diene: