Deck 14: Aromaticity

Question 1

Which of these ions is aromatic? Assume all structures are planar.

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

Answer 1

I and II

Question 2

Which of these conditions is not a requirement for aromaticity?

A) planarity
B) (4 n) π
electrons
C) conjugation
D) cyclic structure
E) (4 n+2) π electrons

Answer 2

(4 n) π
electrons

Question 3

Which of these ions is aromatic?

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

Answer 3

I and IV

Question 4

Which of these structures is aromatic?

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

Question 5

Which of tiefe following s strucures is cumene?

A)

B)

C)

D)

E)

Question 6

Which of the following structures is anisole?

A)

B)

C)

D)

E)

Question 7

Which of the following structures is aniline?

A)
B)
C)
D)
E)

Question 8

Which of these ions contains 4n π electrons?

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

Question 9

Which of the following stucucures is ortho-intoctulene?

A)
B)
C)
D)
E)

Question 10

Which statement about the π molecular orbitals in benzene is true?

A)All antibonding orbitals are occupied.
B)Not all the bonding orbitals are occupied.
C)There are no nonbonding orbitals.
D)All the bonding orbitals have different energies.
E)All the antibonding orbitals have different energies.

Question 11

Which of the following structures is meta-bromoaniline?

A)
B)
C)
D)
E)

Question 12

Which of the following structures is aromatic?

A) I, II, III.
B) I, III, IV.
C) I, II, III, IV.
D) III, IV, V.
E) all of them

Question 13

Which of the following is not aromatic?

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

Question 14

The heat of hydrogenation of benzene is

A) equal to 3x the heat of hydrogenation of ethylene.
B) equal to 1.5x the heat of hydrogenation of 1,3 -butadiene.
C) equal to 1.5x the heat of hydrogenation of 1,3 -cyclobutadiene.
D) lower than 3x the heat of hydrogenation of ethylene.
E) higher than 3x the heat of hydrogenation of ethylene.

Question 15

With regard to electrons, which of the following structures is not isoelectronic with the others?

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

Question 16

In the bridged structure shown below, what are the most likely 1H NMR chemical shifts (in ppm) for , respectively?

A) 6.95,7.27 , and 6.20
B) 6.95,7.27 , and 4.02
C) 6.95,7.27 , and 0.51
D) 3.02,3.44 , and 0.51
E) 3.02,3.44 , and 6.20

Question 17

Which of the following statements is false?

A) Benzene undergoes substitution reactions easier than addition reactions.
B) Alternating C-C bonds in benzene have different lengths.
C) Benzene does not undergo Diels-Alder reactions.
D) Hydrogenation of benzene is extremely slow and requires extreme conditions.
E) The double bonds in benzene are conjugated.

Question 18

Which is a Dewar resonance form of benzene?

A) I
B) II
C) III
D) IV
E) All these structures may be considered Dewar resonance forms of benzene.

Question 19

Which of these structures is not aromatic?

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

Question 20

Which of the following ions is not aromatic? Assume all structures are planar

A)

B)

C)

D)

E)

Question 21

Is the cis-CH₂=CH-CH=CH-CH=CH₂ molecule aromatic? Explain why or why not.

Question 22

Compounds W, X, Y and Z are all alkylbenzenes. W reacts with OsO₄ and with NBS. X reacts with NBS , but not OsO₄. Y reacts with neither NBS nor OsO₄ , and Z reacts with OsO₄ but not with NBS . Which of these structures is compound X ?

A)
B)
C)
D)
E) None of these

Question 23

Which of the following compounds has at least one lone pair in an sp² orbital?

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

Question 24

Which of the following structures is the product of the reaction shown here?

A)
B)
C)
D)
E)

Question 25

Which of the following will not react with KMnO₄?

A)
B)
C)
D)
E)

Question 26

There are five resonance structures of 1,2-dimethoxycyclopropenyl cation.Draw all of them.

Question 27

How many isomeric trisubstituted benzenes C₃H₃XYZ are possible?

Question 28

Which of these structures is the major product of the reaction shown?

A)
B)
C)
D)
E)

Question 29

Which is the correct sequence of reactions required to transform the starting material into the product shown?

A) Na /NH₃, then KMnO₄
B) KMnO₄,then Na/NH₃
C) NBS, then KMnO₄
D) KMnO₄, NBS, then Na/ NH₃
E) Na /NH₃, then NBS

Question 30

Which of the following structures is the product of the reaction shown here?

A)
B)
C)
D)
E)

Question 31

How many nonbonding π molecular orbitals are there in furan?

A) 0
B) 1
C) 2
D) 3
E) 5

Question 32

Draw a Frost circle for cyclopentadienyl cation.Include and label all bonding, nonbonding, and antibonding molecular orbitals.Indicate the nonbonding energy level.Put the correct number of electrons in the appropriate orbitals in your drawing.

Question 33

How many resonances could be observed in the ₁H spectrum of Dewar benzene?

Question 34

Which of the following structures is the product of the reaction shown here?

A)
B)
C)
D)
E)

Question 35

Why is cyclopentadiene a stronger acid than cycloheptatriene?

Question 36

Is the compound shown here aromatic? Explain your answer.

Question 37

Place the three molecules shown here in order of increasing acidity.

A)
B)
C)
D)
E)

Question 38

Fill in the blanks: species is the least acidic and species is the most acidic.

A) x ; z
B) x: y
C) y: z
D) z: y
E) z ; x

Question 39

Draw a Frost circle for benzene.Include and label all bonding molecular orbitals and antibonding molecular orbitals.Indicate the nonbonding energy level. Put the correct number of electrons in the appropriate orbitals in your drawing.

Question 40

Place the three molecules shown here in order of increasing basicity.

A)
B)
C)
D)
E)

Question 41

Devise a multistep synthesis for the following transformation.You may use any organic or inorganic reagents of your choice.Show the reagents necessary for each step and the product of each step.

Question 42

Is the compound shown here aromatic? Assume planarity.

Question 43

Draw ortho-methoxytoluene.

Question 44

Devise a multistep synthesis for the following transformation.You may use any organic or inorganic reagents of your choice.Show the reagents necessary for each step and the product of each step.

Question 45

What is the product of the following reaction?

Question 46

Draw the product of the following reaction.

Question 47

Draw meta-xylene.

Question 48

Draw a mechanism for the following transformation.Include all lone pairs of electrons, curved arrows, and formal charges.

Question 49

Which of these two molecules is more reactive in an S_N1 reaction, and why?

Question 50

Draw the product of the following reaction.

Question 51

Draw the structure of styrene.

Question 52

Devise a multistep synthesis for the following transformation.You may use any organic or inorganic reagents of your choice.Show the reagents necessary for each step and the product of each step.

Question 53

Three alkylbenzene isomers of C₁₀H₁₄ undergo various reactions. Compound A reacts with KMnO₄ to give a para substituted benzoic acid. Compound B does not react with KMnO₄. Compound C reacts with KMnO₄ to give benzoic acid. Propose structures for compounds A, B , and C .

Question 54

Draw a Frost circle for pyrrole.Include and label all bonding molecular orbitals and antibonding molecular orbitals.Indicate the nonbonding energy level.Put the correct number of electrons in
the appropriate orbitals in your drawing.

Question 55

Which nitrogen in imidazole is more basic? Explain your answer.

Question 56

In furan, what type of orbital do each of the two lone pairs on oxygen occupy?

Question 57

Draw the structure of toluene.

Question 58

The compound below is called benzofuran. Suggest an isomeric structure containing fused 5 -membered heterocycle. Does it obey the 4n +2 rule?

Question 59

Which of these two molecules is more reactive in an S_N2 reaction, and why?

Question 60

Draw the structures of the following compounds and place them in the order of increasing boiling points: toluene, p-ethyltoluene, p-ethylbenzoic acid, p-diethylbenzene.

Question 61

Draw an arrow-pushing mechanism for the following transformation.Include all lone pairs and single electrons, curved arrows, and formal charges.Indicate the relative rate of each step.

Question 62

Draw a complete mechanism for the following transformation.Include all lone pairs and single
electrons, curved arrows, and formal charges.Include all significant resonance structures.

Question 63

Devise a multistep synthesis for the following transformation.You may use any organic or inorganic reagents of your choice.Show the reagents necessary for each step and the product of each step.

Question 64

Draw the product of the following reaction.

Question 65

Devise a multistep synthesis for the following transformation.You may use any organic or inorganic reagents of your choice.Show the reagents necessary for each step and the product of each step.

Question 66

Draw the product of the following reaction.