Deck 8: Delocalized Electrons: Their Effect on Stability, pka, and the Products of a Reaction - Aromaticity and Electronic Effects: an Introduction to the Reactions of Benzene

Question 1

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

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

Answer 1

is longer than the carbon-oxygen bond of acetone,(CH₃)₂CO.

Question 2

Mark the most electron-rich carbon atom in the compound below with an asterisk.

Answer 2

Question 3

Which of the following pairs are resonance structures?

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

Answer 3

III

Question 4

Does the following structures represent different compounds or resonance contributors?

Question 5

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 bond length is longer than that of ethane.
D)It is a planar molecule.
E)The carbon-hydrogen bonds are not the same length.

Question 6

Draw the important resonance contributing forms for the structure shown below.

Question 7

In which of the following does resonance delocalization of electron density not play a role?

A)allyl cation
B)benzyl anion
C)CO₃^2-
D)O₃
E)cyclohexyl radical

Question 8

Draw the important resonance structure of

Question 9

Identify the resonance hybrid.

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

Question 10

Draw the important resonance contributing forms for the structure shown below.

Question 11

Give the hybridization,shape,and bond angle of a carbon in benzene.

Question 12

Draw two other resonance contributors for the following compound.

Question 13

Which of the following statements is incorrect about benzene?

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

Question 14

Which of the following is not a resonance structure of the species shown?

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

Question 15

Which of the following pairs are resonance structures?

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

Question 16

The delocalized π system in benzene is formed by a cyclic overlap of 6 ________ orbitals.

A)s
B)p
C)sp
D)sp²
E)sp³

Question 17

Draw the important resonance structures of

Question 18

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

Question 19

Draw the important resonance structures of

Question 20

Draw the important resonance contributing forms for the structure shown below.

Question 21

Which of the following is the strongest acid?

Question 22

Identify the most stable structure(s).

A)CH₂ CH-OCH₃
B)CH₂-CH OCH₃
C)
D)
E)

Question 23

Which of the following is the most stable resonance contributor to acetic acid?

A)
B)
C)
D)
E)

Question 24

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

A)The fewer nearly equivalent resonance contributors are in the structure,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 25

Draw all major resonance contributors of the species below.

Question 26

What is suggested by the fact that benzene's molar heat of hydrogenation is 36 kcal less than three times the molar heat of hydrogenation of cyclohexene?

Question 27

Provide the major organic product of the following reaction.

Question 28

Identify the correctly drawn arrows.

A)
B)
C)
D)
E)

Question 29

Aromatic molecules contain ________ π electrons.

A)no
B)4n + 2 (with n an integer)
C)4n + 2 (where n = 0.5)
D)4n (with n an integer)
E)unpaired

Question 30

In the acetate ion (CH₃CO₂^-),which of the oxygen atoms bears a greater negative charge? Explain your answer.

Question 31

Draw all major resonance contributors of the species below.

Question 32

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

Question 33

Stabilization of a charged species usually happens when this species can be more accurately depicted as a hybrid of several resonance contributing forms.Why is this the case?

Question 34

Provide the major organic product of the following reaction.

Question 35

Rate the following molecules in decreasing order of stability.

Question 36

The following molecule is not aromatic.Why?

Question 37

Draw all major resonance contributors of the species below.

Question 38

Is the following molecule aromatic? Explain.

Question 39

Draw four resonance contributors for the following structure and indicate which is the most important contributor.Explain.

Question 40

Draw all major resonance contributors of the species below.

Question 41

Classify the compound below as aromatic,antiaromatic,or nonaromatic.Assume planarity of the π network.

Question 42

Classify cyclopheptatrienyl cation as aromatic,antiaromatic,or nonaromatic.Assume planarity of the π network.

Question 43

Classify the compound below as aromatic,antiaromatic,or nonaromatic.Assume planarity of the π network.

Question 44

Which of the following compounds is aromatic?

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

Question 45

Which of the following is aromatic?

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

Question 46

Provide the structure of the biologically significant heterocycle pyrimidine.

Question 47

Is cyclooctatetraene a planar molecule? Explain.

Question 48

Which of the following is an aromatic hydrocarbon?

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

Question 49

Classify cyclopentadienyl cation as aromatic,antiaromatic,or nonaromatic.Assume planarity of the π network.

Question 50

Provide the structure of indole.

Question 51

Which of the following is aromatic?

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

Question 52

When cycloheptatriene is deprotonated,an anion with seven resonance forms of equal energy can be drawn.Given this fact,explain why cycloheptatriene is only slightly more acidic than propene.

Question 53

Which of the structures below would be aromatic?

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

Question 54

Provide the structure of the biologically significant heterocycle purine.

Question 55

Is the following molecule aromatic? Explain.

Question 56

Cyclic hydrocarbons which can be represented as structures containing alternating single and double bonds are called ________.

Question 57

Which of the following is aromatic?

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

Question 58

One of the following compounds is aromatic and the other is antiaromatic.Which is which?

Question 59

Which of the following is aromatic?

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

Question 60

Which of the following is antiaromatic?

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

Question 61

What descriptive term is applied to the type of diene represented by 2,4-hexadiene?

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

Question 62

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

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

Question 63

Which of the following is a benzylic cation?

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

Question 64

Among a series of isomeric trienes,the more negative the ΔH° of the hydrogenation reaction of a given triene,the ________ stable it is relative to the others in the isomeric series.

Question 65

Which of the following is an allylic cation?

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

Question 66

Draw the distribution of π electrons in the molecular orbitals of cyclobutadiene.

Question 67

Which of the following is the most stable cation?

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

Question 68

What is the hybridization of the central carbon of allene (1,2-propadiene)?

A)sp
B)sp²
C)sp³
D)p
E)none of the above

Question 69

Rank the following dienes in order of increasing stability: trans-1,3-pentadiene,cis-1,3-pentadiene,1,4-pentadiene,and 1,2-pentadiene.

Question 70

Which of the following numbered hydrogens is most easily abstracted by heterolytic cleavage? Explain.

Question 71

Indicate whether the following molecule is aromatic,antiaromatic,or nonaromatic.

Question 72

Which of the following compounds is more stable? Explain.

Question 73

Which of the following is the most stable diene?

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

Question 74

Which of the following is a cumulated diene?

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

Question 75

How many allylic hydrogen atoms are present in the following molecule?

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

Question 76

Which species is represented by the following distribution of p electrons in the molecular energy diagram?

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

Question 77

Which of the following is a conjugated diene?

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

Question 78

Which of the following statements about the π molecular orbital description of cyclobutadiene is not correct?

A)Cyclobutadiene has two degenerate nonbonding π molecular orbitals.
B)Cyclobutadiene has a single bonding π molecular orbital.
C)Cyclobutadiene has two electrons in nonbonding π molecular orbitals.
D)Cyclobutadiene has one electron in an antibonding π molecular orbital which makes it antiaromatic.
E)none of the above

Question 79

What descriptive term is applied to the type of diene represented by 1,5-octadiene?

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

Question 80

How many benzylic hydrogens are present in the following molecule?

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