Deck 21: Benzene and the Concept of Aromaticity

Question 1

Which of the following compounds is aromatic?

A) ethane
B) cyclobutadiene
C) benzene
D) cyclooctatetraene

Answer 1

benzene

Question 2

What is the correct assignment of the names of the following heterocycles?

A) 1 = pyrrole; 2 = thiophene; 3 = pyridine
B) 1 = thiophene; 2 = furan; 3 = pyrrole
C) 1 = furan; 2 = pyrrole; 3 = thiophene
D) 1 = furan; 2 = thiophene; 3 = pyrrole

Answer 2

1 = furan; 2 = pyrrole; 3 = thiophene

Question 3

Which is the correct assignment of the names of the following substituted benzenes?

A) 1 = phenol; 2 = m-cresol; 3 = toluene
B) 1 = m-cresol; 2 = resorcinol; 3 = m-xylene
C) 1 = anisole; 2 = catechol; 3 = m-xylene
D) 1 = m-cresol; 2 = anisole; 3 = cumene

Answer 3

1 = m-cresol; 2 = resorcinol; 3 = m-xylene

Question 4

Which orbitals contain the lone pairs on the nitrogen atoms labeled i and ii in the imidazole ring?

A) i = sp^2;; ii = sp³
B) i = p^;; ii = sp³
C) i = p^;; ii = sp³.
D) i = p^;; ii = sp²

Question 5

What is the IUPAC name of the following compound?

A) 1-bromo-2-fluoro-4-toluene
B) 4-bromo-2-fluorotoluene
C) 2-bromo-4-fluorophenol
D) 4-bromo-2-fluoroxylene

Question 6

Which orbital contains the lone pair on the nitrogen atom of pyridine?

A) s
B) p
C) sp
D) sp²

Question 7

Which of the following is not one of Hückel's criteria for aromaticity?

A) The compound must be cyclic
B) The compound must have one p-orbital on each atom of a ring
C) The compound must be planar or nearly planar so that there is a continuous overlap of p orbitals
D) The compound must have a closed loop of six pi electrons

Question 8

What is the approximate length of the carbon-carbon bonds in benzene?

A) 110 pm
B) 121 pm
C) 139 pm
D) 156 pm

Question 9

What is the hybridization of the oxygen atom of furan?

A) s
B) sp
C) sp²
D) sp³

Question 10

What is the IUPAC name of the following compound?

A) 2,4-dibromotoluene
B) 2,4-dibromophenol
C) 2,4-dibromohydroxybenzene
D) 4,6-dibromophenol

Question 11

What is the hybridization of the nitrogen atom of pyridine?

A) s
B) sp
C) sp²
D) sp³

Question 12

Which of the following represents the energy levels of the molecular orbitals of benzene?

A) 1
B) 2
C) 3
D) 4

Question 13

What is the correct assignment of the names of the following substituted benzenes?

A) 1 = phenol; 2 = aniline; 3 = anisole
B) 1 = benzaldehyde; 2 = anisole; 3 = toluene
C) 1 = anisole; 2 = xylene; 3 = toluene
D) 1 = anisole; 2 = aniline; 3 = toluene

Question 14

What is the IUPAC name of the following compound?

A) 2-nitro-6-carboxybromobenzene
B) 2-bromo-1-nitro-4-benzoic acid
C) 2-bromo-4-carboxynitrobenzene
D) 3-bromo-4-nitrobenzoic acid

Question 15

Which of the following statements is not true about the structure of benzene?

A) six atomic 2p-orbitals overlap to form six p-molecular orbitals
B) there are three bonding p-molecular orbitals and three p-antibonding molecular orbitals
C) the ground state electronic configuration of benzene has six electrons in three p-bonding molecular orbitals
D) the bonds alternate in length around the ring

Question 16

Which orbital contains the lone pair on the nitrogen atom of pyrrole?

A) s
B) p
C) sp
D) sp²

Question 17

What is the correct assignment of the names of the following fused arenes?

A) 1 = naphthalene; 2 = anthracene; 3 = pyrene
B) 1 = naphthalene; 2 = phenanthrene; 3 = coronene
C) 1 = naphthalene; 2 = anthracene; 3 = benzo[a]pyrene
D) 1 = anthracene; 2 = naphthalene; 3 = coronene

Question 18

What is the correct assignment of the names of the following heterocycles?

A) 1 = pyrrole; 2 = thiophene; 3 = pyridine
B) 1 = thiophene; 2 = furan; 3 = pyrrole
C) 1 = pyridine; 2 = thiophene; 3 = furan
D) 1 = pyridine; 2 = thiophene; 3 = pyrrole

Question 19

Which of the following statements is not true about the structure of benzene?

A) the carbon-carbon bonds are all the same length
B) the structure rapidly transforms between two resonance contributors
C) the structure is an average of two resonance contributors
D) the ring of six carbon atoms is planar

Question 20

What is the correct assignment of the names of the following substituted benzenes?

A) 1 = styrene; 2 = benzaldehyde; 3 = cumene
B) 1 = anisole; 2 = benzaldehyde; 3 = toluene
C) 1 = styrene; 2 = xylene; 3 = toluene
D) 1 = aniline; 2 = phenol; 3 = cumene

Question 21

Which of the following heterocycles is not aromatic?

A) 1
B) 2
C) 3
D) 4

Question 22

Which of the following ions is aromatic?

A) 1
B) 2
C) 3
D) 4

Question 23

What is the major organic product obtained from the following reaction?

A) 1
B) 2
C) 3
D) 4

Question 24

What is the major organic product obtained from the following reaction?

A) 1
B) 2
C) 3
D) 4

Question 25

What is the best choice of reagent to achieve the following reaction?

A) H₂SO₄
B) NaOH, H₂O
C) K₂Cr₂O₇, H₂SO₄
D) H₂/Pd

Question 26

Which of the following has the compounds shown in the correct order of decreasing acidity (i.e., more acidic > less acidic)?

A) 1 > 2 > 3
B) 2 > 3 > 1
C) 3 > 2 > 1
D) 1 > 3 > 2

Question 27

Which of the following has the compounds shown in the correct order of decreasing acidity (i.e., more acidic > less acidic)?

A) 1 > 2 > 3
B) 2 > 1 > 3
C) 3 > 2 > 1
D) 1 > 3 > 2

Question 28

What is the best choice of reagent to achieve the following reaction?

A) Br₂, CCl₄
B) HBr, H₂O
C) Br₂, light
D) NaBr

Question 29

What is the major organic product obtained from the following reaction?

A) 1
B) 2
C) 3
D) 4

Question 30

What is the best choice of reagent to achieve the following reaction?

A) H₂SO₄
B) NaOH, H₂O
C) K₂Cr₂O₇, H₂SO₄
D) LiAlH₄

Question 31

Which of the following represents the energy levels of the molecular orbitals of cyclopentadienyl anion?

A) 1
B) 2
C) 3
D) 4

Question 32

Which of the following molecules is the most acidic?

A) 1
B) 2
C) 3
D) 4

Question 33

Which of the following has the compounds shown in the correct order of decreasing acidity (i.e., more acidic > less acidic)?

A) 1 > 2 > 3
B) 2 > 3 > 1
C) 3 > 2 > 1
D) 2 > 1 > 3

Question 34

Which of the following compounds undergoes heterolytic carbon-halogen bond cleavage to form a stable organic cation?

A) 1
B) 2
C) 3
D) 4

Question 35

Which of the following compounds is antiaromatic?

A) ethane
B) cyclobutadiene
C) benzene
D) cyclooctatetraene

Question 36

What is the major organic product obtained from the following reaction?

A) 1
B) 2
C) 3
D) 4

Question 37

Which of the following has the compounds shown in the correct order of decreasing acidity (i.e., more acidic > less acidic)?

A) 1 > 2 > 3
B) 2 > 3 > 1
C) 3 > 2 > 1
D) 1 > 3 > 2

Question 38

Which of the following has the compounds shown in the correct order of decreasing acidity (i.e., more acidic > less acidic)?

A) 1 > 2 > 3
B) 2 > 1 > 3
C) 3 > 2 > 1
D) 1 > 3 > 2

Question 39

What is the major organic product obtained from the following reaction?

A) 1
B) 2
C) 3
D) 4

Question 40

What is the major organic product obtained from the following reaction?

A) 1
B) 2
C) 3
D) 4

Question 41

What is the major organic product obtained from the following reaction?

Question 42

Which of the following does not undergo oxidation in the presence of H₂CrO₄?

A) 1
B) 2
C) 3
D) 4

Question 43

What is the intermediate in the reaction of ethylbenzene with NBS in the presence of benzoyl peroxide to give 1-bromo-1-phenylethane?

A) Benzylic anion
B) Benzylic cation
C) Benzylic radical
D) Benzylic carbene

Question 44

Which of the following is not true about cyclooctatetraene?

A) The planar conformation is antiaromatic
B) In the planar conformation there are two electrons in degenerate nonbonding pi orbitals.
C) In the tub conformation the pi system is not conjugated
D) The tub conformation is aromatic

Question 45

Which of the following is not true about [the bridged [10]annulene shown below?

A) all of the carbon atoms of bridged [10]annulene are all in the same plane
B) bridged [10]annulene is aromatic
C) bridged [10]annulene undergoes substitution reactions similar to benzene
D) bridged [10]annulene has 10 pi electrons

Question 46

What are the relative positions of the substituents in the following structure?

A) anti
B) meta
C) ortho
D) para

Question 47

List all of the requirements of a molecule for it to be considered aromatic.

Question 48

Provide a brief explanation of why furan (below) is aromatic. Your answer should identify the hybridization of the oxygen atom and account for which electrons are in the pi system.

Question 49

What are the relative positions of the substituents in the following structure?

A) anti
B) meta
C) ortho
D) para

Question 50

What are the two major organic products obtained from the following reaction?

Question 51

What are the relative positions of the substituents in the following structure?

A) anti
B) meta
C) ortho
D) para

Question 52

What is the major organic product obtained from the following reaction?

Question 53

Provide a brief explanation of why the cyclopentadienyl anion (below) is aromatic. Your answer should identify the hybridization of each carbon atom and account for which electrons are in the pi system.

Question 54

Which of the following represents the energy levels of the molecular orbitals of cyclobutadiene?

A) 1
B) 2
C) 3
D) 4

Question 55

Which of the following is not true about [18]annulene?

A) [18]annulene is planar
B) [18]annulene is aromatic
C) [18]annulene gives one peak in the ¹H NMR spectrum
D) [18]annulene has 18 pi bonds

Question 56

How many p orbital electrons are present in cyclopentadienyl anion?

A) 4
B) 6
C) 7
D) 8

Question 57

Which of the following is true about [10]annulene?

A) [10]annulene is planar
B) [10]annulene is nonaromatic
C) [10]annulene undergoes addition reactions similar to simple alkenes
D) [10]annulene has 10 pi electrons

Question 58

How many p orbital electrons are present in furan?

A) 4
B) 6
C) 7
D) 8

Question 59

What is the major organic product obtained from the following reaction?