Chapter 14 - Test Bank Chem 200

Package title: Solomons Test Bank Course Title: Solomons 11e Chapter Number: 14

Question type: Multiple choice

1) The correct name for the compound shown below is:

HO Cl

a) m-chorophenol b) o-chorophenol c) p-chorophenol d) o-chorobenzyl alcohol e) 2-chlorophenyl alcohol Answer: B Topic: Nomenclature and Isomerism Section: 14.2 Difficulty Level: Easy

2) The correct name for the compound shown below is: Br

NH 2

a) m-bromoaniline b) o-bromoaniline c) p-bromoaniline d) o-bromobenzyl amine e) 3-bromophenyl amine Answer: A Topic: Nomenclature and Isomerism Section: 14.2 Difficulty Level: Easy

1

3) The correct name for the compound shown below is: OCH3 O2N

a) o-nitroanisole b) m-nitroanisole c) p-nitroanisole d) p-nitrotoluene e) 4-nitrophenol Answer: C Topic: Nomenclature and Isomerism Section: 14.2 Difficulty Level: Easy

4) The correct name for the compound shown below is:

Br CH 3

a) 3-bromobenzene b) 4-bromobenzene c) m-bromobenzene d) o-bromotoluene e) Bromomethylbenzene Answer: D Topic: Nomenclature and Isomerism Section: 14.2 Difficulty Level: Easy

5) Which of the following is NOT 2-bromo-5-nitrobenzoic acid?

2

Br

Br HO

OH

O2N

NO2

O

O

O

NO2

HO Br

II

I

III HO

Br

O

Br

HO O

NO2

IV

NO2

V

a) I b) II c) III d) IV e) V Answer: D Topic: Nomenclature and Isomerism Section: 14.2 Difficulty Level: Easy

6) Toluene is the name commonly assigned to: a) Hydroxybenzene b) Aminobenzene c) Methylbenzene d) Ethylbenzene e) Methoxybenzene Answer: C Topic: Nomenclature and Isomerism Section: 14.2 Difficulty Level: Easy

7) Anisole is the name commonly assigned to: a) Hydroxybenzene b) Aminobenzene c) Methylbenzene d) Ethylbenzene 3

e) Methoxybenzene Answer: E Topic: Nomenclature and Isomerism Section: 14.2 Difficulty Level: Medium

8) Phenol is the name commonly assigned to: a) Hydroxybenzene b) Aminobenzene c) Methylbenzene d) Ethylbenzene e) Methoxybenzene Answer: A Topic: Nomenclature and Isomerism Section: 14.2 Difficulty Level: Medium

9) Aniline is the name commonly assigned to: a) Hydroxybenzene b) Aminobenzene c) Methylbenzene d) Ethylbenzene e) Methoxybenzene Answer: B Topic: Nomenclature and Isomerism Section: 14.2 Difficulty Level: Medium

10) Xylene is the name commonly assigned to: a) Hydroxybenzene b) Aminobenzene c) Dimethylbenzene d) Ethylbenzene e) Methoxybenzene 4

Answer: C Topic: Nomenclature and Isomerism Section: 14.2 Difficulty Level: Medium

11) Cumene is the name commonly assigned to: a) Hydroxybenzene b) Aminobenzene c) Ethylbenzene d) Isopropylbenzene e) Isobutylbenzene Answer: D Topic: Nomenclature and Isomerism Section: 14.2 Difficulty Level: Medium

12) The correct name for the compound shown below is: Br Br NH2

a) 3,4-Dibromoaniline b) 2,4-Dibromoaniline c) 2,5-Dibromoaniline d) 3,6-Dibromoaniline e) 2,6-Dibromoaniline Answer: C Topic: Nomenclature and Isomerism Section: 14.2 Difficulty Level: Medium

13) 2-Bromo-4-nitroaniline is:

5

Br

Br NH2 Br

NO2

NO2 NH2

NO2

I

II

H2N

III

OCH3

Br

Br

H3CO NO2

NO2

IV

V

a) I b) II c) III d) IV e) V Answer: C Topic: Nomenclature and Isomerism Section: 14.2 Difficulty Level: Medium

14) 2-Bromo-5-nitroaniline is: Br

Br NH2 Br

NO2

NO2 NH2

NO2

I

II

H2N

III

OCH3 Br

Br H3CO

NO2

NO2

IV

V

a) I b) II c) III d) IV e) V

6

Answer: B Topic: Nomenclature and Isomerism Section: 14.2 Difficulty Level: Medium

15) 2-Bromo-4-nitroaniline is: Br

Br NH2 Br

NO2

NO2 NH2

NO2

I

II

H2N

III

OCH3 Br

Br H3CO

NO2

NO2

IV

V

a) I b) II c) III d) IV e) V Answer: C Topic: Nomenclature and Isomerism Section: 14.2 Difficulty Level: Medium

16) m-chlorobenzenesulfonic acid is:

7

Cl Cl

SO 3HCl

SO3 H Cl

SO 3H

I

II HO3 S

HOOC

III HOOC

Cl

Cl

IV

V

a) I b) II c) III d) IV e) V Answer: D Topic: Nomenclature and Isomerism Section: 14.2 Difficulty Level: Medium

17) 4-Bromo-2-nitroaniline is: Br

Br NH2 Br

NO2

NO2 NH2

NO2

I

II

H2N

III

OCH3 Br

Br H3CO

NO2

NO2

IV

V

a) I b) II c) III d) IV e) V 8

Answer: A Topic: Nomenclature and Isomerism Section: 14.2 Difficulty Level: Medium

18) 4-Amino-2-chlorophenol is: Cl

OH

Cl

O

O

Cl NH2

NO2

I

II

H2N

III

OH

OH

Cl

Cl

NH2

NO2

IV

V

a) I b) II c) III d) IV e) V Answer: D Topic: Nomenclature and Isomerism Section: 14.2 Difficulty Level: Medium

19) 3-bromo-4-nitroacetophenone is: Br

O

O

O Br

H O2 N

O 2N

O 2N

I

Br

H

II

III O

O O 2N

O 2N

H

Br

Br

IV

V 9

a) I b) II c) III d) IV e) V Answer: C Topic: Nomenclature and Isomerism Section: 14.2 Difficulty Level: Medium

20) 4-Chloro-3-nitro-benzaldehyde is: Cl

OH

Cl

O

O

Cl NH2

NO2

I

II

H2N

III

OH Cl

OH Cl

NH2

NO2

IV

V

a) I b) II c) III d) IV e) V Answer: B Topic: Nomenclature and Isomerism Section: 14.2 Difficulty Level: Medium

21) 4-Amino-2-chlorobenzaldehyde is:

10

Cl

OH

Cl

O

O

Cl NH2

NO2

I

II

H2N

III

OH

OH

Cl

Cl

NH2

NO2

IV

V

a) I b) II c) III d) IV e) V Answer: C Topic: Nomenclature and Isomerism Section: 14.2 Difficulty Level: Medium

22) 4-Amino-2-bromoanisole is: Br

Br

Br

OCH3

O

H3CO NH2

NO2

I

II

H2N

III

OCH3 Br

OCH3 Br

NH2

NO2

IV

V

a) I b) II c) III d) IV e) V Answer: D Topic: Nomenclature and Isomerism 11

Section: 14.2 Difficulty Level: Medium

23) 4-Bromomethyl-2-nitroanisole is: Br

Br

Br

OCH3

O

H3CO NH2

NO2

I

II

H2N

III

OCH3

OCH3

Br

Br

NH2

NO2

IV

V

a) I b) II c) III d) IV e) V Answer: B Topic: Nomenclature and Isomerism Section: 14.2 Difficulty Level: Medium

24) 3-chloro-4-nitrobenzoic acid is: Cl

O

O

O Cl

H O2 N

O 2N

O 2N

I

Cl

OH

II

III O

O O 2N

O 2N

H

Cl

Cl

IV

V

a) I 12

b) II c) III d) IV e) V Answer: B Topic: Nomenclature and Isomerism Section: 14.2 Difficulty Level: Medium

25) In theory, a single molecule of this compound will rotate plane-polarized light. a) Butylbenzene b) Isobutylbenzene c) sec-Butylbenzene d) tert-Butylbenzene e) None of these choices. Answer: C Topic: Nomenclature and Isomerism Section: 14.2 Difficulty Level: Medium

26) Which dichlorobenzene might theoretically yield three mononitro products? a) o-Dichlorobenzene b) m-Dichlorobenzene c) p-Dichlorobenzene d) None of these choices. e) All of these choices. Answer: B Topic: Nomenclature and Isomerism Section: 14.2 and 14.3 Difficulty Level: Medium

27) Which dibromobenzene can yield only one mononitro derivative? a) o-Dibromobenzene b) m-Dibromobenzene 13

c) p-Dibromobenzene d) More than one of these choices. e) None of these choices. Answer: C Topic: Nomenclature and Isomerism Section: 14.2 and 14.3 Difficulty Level: Medium

28) If thiophene is an aromatic molecule and reacts similarly to benzene, how many (neutral) monobromothiophenes could be obtained in the following reaction? S

Br2 FeBr3

a) 1 b) 2 c) 3 d) 4 e) 5 Answer: B Topic: Nomenclature and Isomerism Section: 14.3 Difficulty Level: Medium

29) Which of these is the single best representation for naphthalene?

II

I

IV

III

V

a) I b) II c) III d) IV e) V 14

Answer: A Topic: Nomenclature and Isomerism Section: 14.8 Difficulty Level: Medium

30) How many dichloronaphthalenes are possible? a) 7 b) 8 c) 9 d) 10 e) 12 Answer: D Topic: Nomenclature and Isomerism Section: 14.2 and 14.8 Difficulty Level: Hard

31) How many monochloronaphthalenes are possible? a) 2 b) 3 c) 4 d) 5 e) 6 Answer: A Topic: Nomenclature and Isomerism Section: 14.2 and 14.8 Difficulty Level: Hard

32) The complete name for the following compound is: CH3

H

a) sec-Hexylbenzene b) 2-Phenylhexane c) (R)-2-Phenylhexane 15

d) (S)-2-Phenylhexane e) Butylmethylphenylmethane Answer: D Topic: Nomenclature and Isomerism Section: 5.7 and 14.2 Difficulty Level: Hard

33) The complete name for the following compound is: CH3

H

a) sec-Hexylbenzene b) 2-Phenylhexane c) (R)-2-Phenylhexane d) (S)-2-Phenylhexane e) Butylmethylphenylmethane Answer: C Topic: Nomenclature and Isomerism Section: 5.7 and 14.2 Difficulty Level: Hard

34) Which dibromobenzene can, in theory, yield three mononitro derivatives? a) o-Dibromobenzene b) m-Dibromobenzene c) p-Dibromobenzene d) All of these choices. e) None of these choices. Answer: B Topic: Nomenclature and Isomerism Section: 14.3 Difficulty Level: Hard

35) Which dihydroxybenzene can yield only one mononitro derivative? 16

a) o-Dihydroxybenzene b) m-Dihydroxybenzene c) p- Dihydroxybenzene d) More than one of these choices. e) None of these choices. Answer: C Topic: Nomenclature and Isomerism Section: 14.2 and 14.3 Difficulty Level: Hard

36) How many different dibromophenols are possible? a) 8 b) 7 c) 6 d) 5 e) 4 Answer: C Topic: Nomenclature and Isomerism Section: 14.2 and 14.3 Difficulty Level: Hard

37) How many different dichloronitrobenzenes are possible? a) 8 b) 7 c) 6 d) 5 e) 4 Answer: C Topic: Nomenclature and Isomerism Section: 14.2 and 14.3 Difficulty Level: Hard

38) How many different dihydroxybromobenzenes are possible?

17

a) 8 b) 7 c) 6 d) 5 e) 4 Answer: C Topic: Nomenclature and Isomerism Section: 14.2 and 14.3 Difficulty Level: Hard

39) Which is the only one of these reagents which will react with benzene under the specified conditions? a) Cl2, FeCl3, heat b) H2, 25°C c) Br2/CCl4, 25°C, dark d) KMnO4/H2O, 25°C e) H3O+, heat Answer: A Topic: Chemical Tests and Reactions Section: 14.3 Difficulty Level: Easy

40) Which reagent(s) would serve as the basis for a simple chemical test that would distinguish between benzene and 1-hexene? a) NaOH in H2O b) Br2 in CCl4 c) AgNO3 in C2H5OH d) NaHSO3 in H2O e) None of these choices. Answer: B Topic: Chemical Tests and Reactions Section: 14.3 Difficulty Level: Medium

41) Which reagent(s) would serve as the basis for a simple chemical test that would distinguish 18

between benzene and cyclohexene? a) NaOH in H2O b) Br2 in CCl4 c) AgNO3 in C2H5OH d) NaHSO3 in H2O e) None of these choices. Answer: B Topic: Chemical Tests and Reactions Section: 14.3 Difficulty Level: Medium

42) Which reagent(s) would serve as the basis for a simple chemical test that would distinguish between ethylbenzene and vinylcyclohexane? a) H2CrO4 b) LAH c) NaBH4, H2O d) KMnO4, OH−, H2O e) Two of these choices. Answer: D Topic: Chemical Tests and Reactions Section: 14.3 Difficulty Level: Medium

43) Which reagent(s) would serve as the basis for a simple chemical test that would distinguish between ethylbenzene and vinylcyclohexane? a) H2CrO4 b) LAH c) NaBH4, H2O d) O3/Zn, H+ e) Two of these choices. Answer: D Topic: Chemical Tests and Reactions Section: 14.3 Difficulty Level: Medium

19

44) Which reagent(s) would serve as the basis for a simple chemical test that would distinguish between naphthalene and 2,4,6-decatriene? a) NaOH in H2O b) KMnO4, OH−, H2O c) NaBH4, H2O d) H2CrO4 e) None of these choices. Answer: B Topic: Chemical Tests and Reactions Section: 14.3 Difficulty Level: Medium

45) Why would 1,3-cyclohexadiene undergo dehydrogenation readily? a) It is easily reduced. b) Hydrogen is a small molecule. c) 1,3-Cyclohexadiene has no resonance energy. d) It would gain considerable stability by becoming benzene. e) It would not undergo dehydrogenation. Answer: D Topic: Explanations and Predictions Section: 14.5 Difficulty Level: Medium 46) Recalling that benzene has a resonance energy of 152 kJ mol-1 and naphthalene has a resonance energy of 255 kJ mol-1, predict the positions which would be occupied by bromine when phenanthrene (below) undergoes addition of Br2.

3

4

5

6

2

7 1

8 10

9

a) 1, 2 b) 1, 4 c) 3, 4 d) 7, 8 20

e) 9, 10 Answer: E Topic: Explanations and Predictions Section: 14.3 and 14.5 Difficulty Level: Medium

47) Which of the following statements about cyclooctatetraene is NOT true? a) The compound rapidly decolorizes Br2/CCl4 solutions. b) The compound rapidly decolorizes aqueous solutions of KMnO4. c) The compound readily adds hydrogen. d) The compound is nonplanar. e) The compound is comparable to benzene in stability. Answer: E Topic: Explanations and Predictions Section: 14.5 and 14.7 Difficulty Level: Medium

48) Cyclopentadiene is unusually acidic for a hydrocarbon. An explanation for this is the following statement. a) The carbon atoms of cyclopentadiene are all sp2-hybridized. b) Cyclopentadiene is aromatic. c) Removal of a proton from cyclopentadiene yields an aromatic anion. d) Removal of a hydrogen atom from cyclopentadiene yields a highly stable free radical. e) Removal of a hydride ion from cyclopentadiene produces an aromatic cation. Answer: C Topic: Explanations and Predictions Section: 14.5 and 14.7 Difficulty Level: Medium

49) Consider the molecular orbital model of benzene. In the ground state how many molecular orbitals are filled with electrons? a) 1 b) 2 c) 3 21

d) 4 e) 5 Answer: C Topic: Molecular Orbital Theory Section: 14.6 Difficulty Level: Medium

50) In the molecular orbital model of benzene, how many pi-electrons are delocalized about the ring? a) 2 b) 3 c) 4 d) 5 e) 6 Answer: E Topic: Molecular Orbital Theory Section: 14.6 Difficulty Level: Medium

51) In the molecular orbital model of benzene, how many pi-electrons are in bonding molecular orbitals? a) 6 b) 5 c) 4 d) 3 e) 2 Answer: A Topic: Molecular Orbital Theory Section: 14.6 Difficulty Level: Medium

52) Which cyclization(s) should occur with a decrease in pi-electron energy?

22

I

CH2

CH

CH

II

CH2

CH

CH2

III CH2

CH

CH2

IV CH2

CH

CH2

CH2

+ H2

+ H2

+ H2

+ H2

a) I b) II c) III d) IV e) All of these choices. Answer: B Topic: Molecular Orbital Theory Section: 14.7 Difficulty Level: Medium

53) Which cyclization(s) should occur with a decrease in pi-electron energy? I

+

H2

II

+

H2

III

+

H2

IV

+

H2

23

a) I b) II c) III d) IV e) All of these choices. Answer: B Topic: Molecular Orbital Theory Section: 14.7 Difficulty Level: Medium

54) Which cyclization(s) should occur with an increase in pi-electron energy?

a) I b) II c) III d) IV e) All of these choices. Answer: D Topic: Molecular Orbital Theory Section: 14.7 Difficulty Level: Medium

55) Which cyclization(s) should occur with an increase in pi-electron energy? 24

a) I b) II c) III d) IV e) All of these choices. Answer: A Topic: Molecular Orbital Theory Section: 14.7 Difficulty Level: Medium

56) Application of the polygon-and-circle technique reveals that single electrons occupy each of the two nonbonding orbitals in the molecular orbital diagram of: a) Cyclobutadiene b) Benzene c) Cyclopropenyl cation d) Cyclopentadienyl anion e) Cycloheptatrienyl cation Answer: A Topic: Molecular Orbital Theory Section: 14.7 Difficulty Level: Medium

57) In the molecular orbital model of benzene, the six p-orbitals combine to form how many 25

molecular orbitals? a) 6 b) 5 c) 4 d) 3 e) 2 Answer: A Topic: Molecular Orbital Theory Section: 14.6 and 14.7 Difficulty Level: Medium 58) In the molecular orbital model of benzene, how many π-bonding molecular orbitals are there? a) 6 b) 5 c) 4 d) 3 e) 2 Answer: D Topic: Molecular Orbital Theory Section: 14.6 and 14.7 Difficulty Level: Medium 59) In the molecular orbital model of benzene, how many π-antibonding molecular orbitals are there? a) 6 b) 5 c) 4 d) 3 e) 2 Answer: D Topic: Molecular Orbital Theory Section: 14.6 and 14.7 Difficulty Level: Medium

26

60) In the molecular orbital model of benzene, how many pairs of degenerate π-molecular orbitals are there? a) 6 b) 5 c) 4 d) 3 e) 2 Answer: E Topic: Molecular Orbital Theory Section: 14.6 and 14.7 Difficulty Level: Medium 61) In the molecular orbital model of benzene, how many pairs of degenerate π-bonding molecular orbitals are there? a) 1 b) 2 c) 3 d) 4 e) 5 Answer: A Topic: Molecular Orbital Theory Section: 14.6 and 14.7 Difficulty Level: Medium 62) In the molecular orbital model of benzene, how many pairs of degenerate π-antibonding molecular orbitals are there? a) 1 b) 2 c) 3 d) 4 e) 5 Answer: A Topic: Molecular Orbital Theory Section: 14.6 and 14.7 27

Difficulty Level: Medium

63) In the molecular orbital model of benzene, how many non-bonding molecular orbitals are there? a) 1 b) 2 c) 3 d) 4 e) 0 Answer: E Topic: Molecular Orbital Theory Section: 14.6 and 14.7 Difficulty Level: Medium 64) In the molecular orbital model of the cyclopentadienyl cation, how many π-bonding molecular orbitals are there? a) 6 b) 5 c) 4 d) 3 e) 2 Answer: D Topic: Molecular Orbital Theory Section: 14.6 and 14.7 Difficulty Level: Medium 65) In the molecular orbital model of the cyclopentadienyl cation, how many π-antibonding molecular orbitals are there? a) 6 b) 5 c) 4 d) 3 e) 2 Answer: E

28

Topic: Molecular Orbital Theory Section: 14.6 and 14.7 Difficulty Level: Medium

66) In the molecular orbital model of the cyclopentadienyl cation, how many pairs of degenerate π-molecular orbitals are there? a) 6 b) 5 c) 4 d) 3 e) 2 Answer: E Topic: Molecular Orbital Theory Section: 14.6 and 14.7 Difficulty Level: Medium

67) In the molecular orbital model of the cyclopentadienyl cation, how many pairs of degenerate π-bonding molecular orbitals are there? a) 1 b) 2 c) 3 d) 4 e) 5 Answer: A Topic: Molecular Orbital Theory Section: 14.6 and 14.7 Difficulty Level: Medium

68) In the molecular orbital model of the cyclopentadienyl cation, how many pairs of degenerate π-antibonding molecular orbitals are there? a) 1 b) 2 c) 3 d) 4 e) 5

29

Answer: A Topic: Molecular Orbital Theory Section: 14.6 and 14.7 Difficulty Level: Medium

69) In the molecular orbital model of the cyclopentadienyl cation, how many non-bonding molecular orbitals are there? a) 1 b) 2 c) 3 d) 4 e) 0 Answer: E Topic: Molecular Orbital Theory Section: 14.6 and 14.7 Difficulty Level: Medium 70) In the molecular orbital model of cyclobutadiene, how many π-bonding molecular orbitals are there? a) 1 b) 2 c) 3 d) 4 e) 5 Answer: A Topic: Molecular Orbital Theory Section: 14.6 and 14.7 Difficulty Level: Medium 71) In the molecular orbital model of cyclobutadiene, how many π-antibonding molecular orbitals are there? a) 5 b) 4 c) 3 d) 2 30

e) 1 Answer: E Topic: Molecular Orbital Theory Section: 14.6 and 14.7 Difficulty Level: Medium 72) In the molecular orbital model of cyclobutadiene, how many pairs of degenerate π-molecular orbitals are there? a) 0 b) 1 c) 2 d) 3 e) 4 Answer: A Topic: Molecular Orbital Theory Section: 14.6 and 14.7 Difficulty Level: Medium 73) In the molecular orbital model of the cyclobutadiene, how many pairs of degenerate πbonding molecular orbitals are there? a) 1 b) 2 c) 3 d) 4 e) 0 Answer: E Topic: Molecular Orbital Theory Section: 14.6 and 14.7 Difficulty Level: Medium 74) In the molecular orbital model of cyclobutadiene, how many pairs of degenerate πantibonding molecular orbitals are there? a) 1 b) 2 31

c) 3 d) 4 e) 0 Answer: E Topic: Molecular Orbital Theory Section: 14.6 and 14.7 Difficulty Level: Medium

75) In the molecular orbital model of cyclobutadiene, how many non-bonding molecular orbitals are there? a) 1 b) 2 c) 3 d) 4 e) 0 Answer: B Topic: Molecular Orbital Theory Section: 14.6 and 14.7 Difficulty Level: Medium

76) Consider the molecular orbital model of cyclopentadienyl anion. In the ground state how many molecular orbitals are filled with electrons? a) 1 b) 2 c) 3 d) 4 e) 5 Answer: C Topic: Molecular Orbital Theory Section: 14.6 and 14.7 Difficulty Level: Medium

77) In the molecular orbital model of cyclopentadienyl anion, how many pi-electrons are delocalized about the ring?

32

a) 2 b) 3 c) 4 d) 5 e) 6 Answer: E Topic: Molecular Orbital Theory Section: 14.6 and 14.7 Difficulty Level: Medium

78) In the molecular orbital model of cyclopentadienyl anion, how many pi-electrons are in bonding molecular orbitals? a) 6 b) 5 c) 4 d) 3 e) 2 Answer: A Topic: Molecular Orbital Theory Section: 14.6 and 14.7 Difficulty Level: Medium

79) In the molecular orbital model of cycloheptadienyl cation, how many pi-electrons are in bonding molecular orbitals? a) 6 b) 5 c) 4 d) 3 e) 2 Answer: A Topic: Molecular Orbital Theory Section: 14.6 and 14.7 Difficulty Level: Medium

80) In the molecular orbital model of cycloheptadienyl cation, how many pi-electrons are 33

delocalized about the ring? a) 6 b) 5 c) 4 d) 3 e) 2 Answer: A Topic: Molecular Orbital Theory Section: 14.6 and 14.7 Difficulty Level: Medium

81) In the molecular orbital model of 1,3-cyclobutadiene, how many electrons are in nonbonding molecular orbitals? a) 6 b) 5 c) 4 d) 3 e) 2 Answer: E Topic: Molecular Orbital Theory Section: 14.6 and 14.7 Difficulty Level: Medium

82) In the molecular orbital model of which of the following substance(s) are non-bonding orbitals found? a) 1,3-Cyclobutadiene b) Cyclopentadienyl anion c) 1,3,5,7-Cyclooctatetraene d) Two of these choices. e) All of these choices. Answer: D Topic: Molecular Orbital Theory Section: 14.6 and 14.7 Difficulty Level: Medium

34

83) Which of the following is NOT true of benzene? a) Benzene tends to undergo substitution rather than addition reactions, even though it has a high index of hydrogen deficiency. b) All of the hydrogen atoms of benzene are equivalent. c) The carbon-carbon bonds of benzene are alternately short and long around the ring. d) Only one o-dichlorobenzene has ever been found. e) Benzene is more stable than the hypothetical compound 1,3,5-cyclohexatriene. Answer: C Topic: Bonding and Resonance Section: 14.4 and 14.6 Difficulty Level: Easy

84) Which of the following is true of benzene? a) Benzene tends to undergo addition rather than substitution reactions. b) All of the hydrogen atoms of benzene are equivalent. c) The carbon-carbon bonds of benzene are alternately short and long around the ring. d) The benzene ring is a distorted hexagon. e) Benzene has the stability expected for cyclohexatriene. Answer: B Topic: Bonding and Resonance Section: 14.4 and 14.6 Difficulty Level: Easy

85) The carbon-carbon bonds in benzene are: a) of equal length and are shorter than the double bond of ethene. b) of equal length and are intermediate between a double bond and a single bond. c) of unequal length and are alternately short and long around the ring. d) due only to p-orbital overlap. e) of equal length and intermediate between the carbon-carbon bond lengths in ethene and ethyne. Answer: B Topic: Bonding and Resonance Section: 14.4 and 14.6 Difficulty Level: Easy 35

86) We now know that the two Kekule structures for benzene are related in the following way: a) They are each equally correct as a structure for benzene. b) Benzene is sometimes one structure and sometimes the other. c) The two structures are in a state of rapid equilibrium. d) Neither of the two structures adequately describes benzene; benzene is a resonance hybrid of the two. e) None of these choices. Answer: D Topic: Bonding and Resonance Section: 14.4 and 14.6 Difficulty Level: Easy

87) In which of the following compounds would the shortest carbon-carbon bond(s) be found? a) Toluene b) 2-Ethylcyclopentene c) 4-Methyl-1,3-cyclohexadiene d) 3-Methyl-1-hexyne e) 3-Methyl-1,3-hexadiene Answer: D Topic: Nomenclature, Bonding and Resonance Section: 14.4 and 14.6 Difficulty Level: Medium

88) In which of the following compounds would the longest carbon-carbon bond(s) be found? a) 2-Bromobenzaldehyde b) Vinylbenzene c) 1,3,5-Heptatriene d) 2,4,6-Octatriene e) 2-Ethylbenzoic acid Answer: D Topic: Nomenclature, Bonding and Resonance Section: 14.4 and 14.6 Difficulty Level: Hard 36

89) Which of the following statements regarding the cyclopentadienyl radical is correct? a) It is aromatic. b) It is not aromatic. c) It obeys Huckel's rule. d) It undergoes reactions characteristic of benzene. e) It has a closed shell of 6 pi-electrons. Answer: B Topic: Aromatic/ Antiaromatic/ Nonaromatic Section: 14.7 Difficulty Level: Medium

90) Which of the following statements regarding the cycloheptatrienyl radical is correct? a) It is aromatic. b) It is not aromatic. c) It obeys Hückel's rule. d) It undergoes reactions characteristic of benzene. e) It has a closed shell of 6 pi-electrons. Answer: B Topic: Aromatic/ Antiaromatic/ Nonaromatic Section: 14.7 Difficulty Level: Medium

91) Which of the following statements regarding the cyclopentadienyl cation is correct? a) It is aromatic. b) It is not aromatic. c) It obeys Hückel’s rule. d) It undergoes reactions characteristic of benzene. e) It has a closed shell of 6 pi-electrons. Answer: B Topic: Aromatic/ Antiaromatic/ Nonaromatic Section: 14.7 Difficulty Level: Medium

37

92) Which of the following statements regarding the cyclopropenyl anion is correct? a) It is aromatic. b) It is not aromatic. c) It obeys Hückel’s rule. d) It undergoes reactions characteristic of benzene. e) It has a closed shell of 6 pi-electrons. Answer: B Topic: Aromatic/ Antiaromatic/ Nonaromatic Section: 14.7 Difficulty Level: Medium

93) Which of the following statements regarding the cyclopropenyl radical is correct? a) It is aromatic. b) It is not aromatic. c) It obeys Hückel’s rule. d) It undergoes reactions characteristic of benzene. e) It has a closed shell of 6 pi-electrons. Answer: B Topic: Aromatic/ Antiaromatic/ Nonaromatic Section: 14.7 Difficulty Level: Medium

94) Which of the following statements regarding the cycloheptatrienyl anion is correct? a) It is aromatic. b) It is not aromatic. c) It obeys Hückel’s rule. d) It undergoes reactions characteristic of benzene. e) It has a closed shell of 6 pi-electrons. Answer: B Topic: Aromatic/ Antiaromatic/ Nonaromatic Section: 14.7 Difficulty Level: Medium

38

95) Of Hückel’s requirements for aromatic character, only this one is waived in the case of certain compounds considered to be aromatic. a) The ring system must be planar. b) The system must be monocyclic. c) There must be (4n + 2) π electrons. d) The Hückel number of electrons must be completely delocalized. e) None. All of these rules must apply in every case. Answer: B Topic: Aromaticity, Hückel’s Rule Section: 14.7 Difficulty Level: Easy

96) Which of the following would you expect to be aromatic? H H

I

II

III

IV

V

a) I b) II c) III d) IV e) V Answer: E Topic: Aromaticity, Huckel’s Rule Section: 14.7 Difficulty Level: Medium

97) Which of the following would you expect to be aromatic? H H

I

II

III

IV

2+ V

a) I b) II 39

c) III d) IV e) V Answer: E Topic: Aromaticity, Hückel’s Rule Section: 14.7 Difficulty Level: Medium

98) Which of the following would you expect to be aromatic?

H H

I

II

III

IV

a) I b) II c) III d) IV e) None of these choices. Answer: B Topic: Aromaticity, Hückel’s Rule Section: 14.7 Difficulty Level: Medium

99) Which of the following would you expect to show aromatic character?

a) I b) II c) III d) IV e) None of these choices. 40

Answer: B Topic: Aromaticity, Hückel’s Rule Section: 14.7 Difficulty Level: Medium

100) Which of the following would you expect to be aromatic?

I

II

III

IV

a) I b) II c) III d) IV e) All of these choices. Answer: A Topic: Aromaticity, Hückel’s Rule Section: 14.7 Difficulty Level: Medium

101) Which of the following would you expect to be aromatic?

a) I b) II c) III d) IV e) All of these choices. Answer: A Topic: Aromaticity, Hückel’s Rule Section: 14.7 Difficulty Level: Medium 41

102) Which of the following would you expect to be aromatic?

a) I b) II c) III d) IV e) All of these choices. Answer: A Topic: Aromaticity, Hückel’s Rule Section: 14.7 Difficulty Level: Medium

103) Which of the following structures would be aromatic?

a) I b) II c) III d) IV e) V Answer: B Topic: Aromaticity, Hückel’s Rule Section: 14.7 Difficulty Level: Medium

42

104) Which of the following would you expect to be aromatic?

H H

I

II

III

IV

a) I b) II c) III d) IV e) None of these choices. Answer: C Topic: Aromaticity, Hückel’s Rule Section: 14.7 Difficulty Level: Medium

105) Which of the following would you expect to be aromatic?

a) I b) II c) III d) IV e) None of these choices. Answer: C Topic: Aromaticity, Hückel’s Rule Section: 14.7 Difficulty Level: Medium

106) On the basis of molecular orbital theory and Hückel’s rule, which molecules and/or ions should be aromatic? 43

I

H

H H

II

III

H

IV

V

N H

H

VI

VII

H

H

VIII

IX

a) I and V b) III and VIII c) IV, VII and IX d) IV, VI, VII and IX e) All of the structures, I-IX Answer: D Topic: Aromaticity, Hückel’s Rule Section: 14.7 Difficulty Level: Medium

107) On the basis of molecular orbital theory and Hückel’s rule, which molecules and/or ions should be antiaromatic?

I

H

H H

II

III

H

IV

V

N H

VI

H

VII

H

H

VIII

IX

a) I and V b) I, II and V c) III and VIII 44

d) IV, VII and IX e) IV, VI, VII and IX Answer: B Topic: Aromaticity, Hückel’s Rule Section: 14.7 Difficulty Level: Medium

108) On the basis of molecular orbital theory and Hückel’s rule, which molecules and/or ions should be non-aromatic?

I

H

H H

II

III

H

IV

V

N H

VI

H

VII

H

H

VIII

IX

a) I and V b) I and II c) III and VIII d) IV, VII and IX e) IV, VI, VII and IX Answer: C Topic: Aromaticity, Hückel’s Rule Section: 14.7 Difficulty Level: Medium

109) On the basis of molecular orbital theory and Hückel’s rule, which of these compounds should be aromatic?

45

H H

I

II

III

IV

V

a) I b) II c) III d) IV e) V Answer: E Topic: Aromaticity, Hückel’s Rule Section: 14.7 Difficulty Level: Medium

110) On the basis of molecular orbital theory and Hückel’s rule, which of these compounds should be aromatic?

a) I b) II c) III d) IV e) V Answer: E Topic: Aromaticity, Hückel’s Rule Section: 14.7 Difficulty Level: Medium

111) On the basis of molecular orbital theory and Hückel’s rule, which of these compounds should be aromatic?

46

a) I b) II c) III d) IV e) V Answer: E Topic: Aromaticity, Hückel’s Rule Section: 14.7 Difficulty Level: Medium

112) Which of these is an aromatic molecule?

N

O

CH3

I

B CH3

II

III

N

S

H

O

IV

V

a) I b) II c) III d) IV e) V Answer: A Topic: Aromaticity, Hückel’s Rule Section: 14.7 Difficulty Level: Medium

113) Which of these is an aromatic molecule?

47

a) I b) II c) III d) IV e) V Answer: A Topic: Aromaticity, Hückel’s Rule Section: 14.7 Difficulty Level: Medium

114) Which of these is an aromatic molecule?

a) I b) II c) III d) IV e) V Answer: A Topic: Aromaticity, Hückel’s Rule Section: 14.7 Difficulty Level: Medium

115) Which of these is an aromatic molecule? 48

a) I b) II c) III d) IV e) V Answer: A Topic: Aromaticity, Hückel’s Rule Section: 14.7 Difficulty Level: Medium

116) Which of these is not an aromatic molecule?

a) I b) II c) III d) IV e) V Answer: D Topic: Aromaticity, Hückel’s Rule Section: 14.7 Difficulty Level: Medium

49

117) Of the following C-10 compounds, which is expected to possess the greatest resonance (delocalization) energy?

I

II

III

IV

V

a) I b) II c) III d) IV e) V Answer: C Topic: Aromaticity, Hückel’s Rule Section: 14.7 and 14.8 Difficulty Level: Medium

118) Which of the following would you expect to be antiaromatic?

I

II

III

IV

V

a) I b) II c) III d) IV e) V Answer: C Topic: Aromaticity, Hückel’s Rule Section: 14.7 and 14.8 Difficulty Level: Medium

119) Which of these would you expect to have significant resonance stabilization energy? 50

N H

N

I

II

III

a) I b) II c) III d) All of these choices. e) None of these choices. Answer: D Topic: Aromaticity, Huckel’s Rule Section: 14.7 and 14.9 Difficulty Level: Medium

120) Which of these would you expect to have significant resonance stabilization energy?

O N

I

II

III

a) I b) II c) III d) All of these choices. e) None of these choices. Answer: D Topic: Aromaticity, Hückel’s Rule Section: 14.7 and 14.9 Difficulty Level: Medium

121) Which of these would you expect to have significant resonance stabilization energy?

51

a) I b) II c) III d) All of these choices. e) None of these choices. Answer: D Topic: Aromaticity, Hückel’s Rule Section: 14.7 and 14.9 Difficulty Level: Medium

122) Which of these would you expect to have significant resonance stabilization energy?

S N

I

II

III

a) I b) II c) III d) All of these choices. e) None of these choices. Answer: D Topic: Aromaticity, Hückel’s Rule Section: 14.7 and 14.9 Difficulty Level: Medium

123) Which of these would you expect to have significant resonance stabilization energy?

52

CH N

II

I

III

a) I b) II c) III d) All of these choices. e) None of these choices. Answer: D Topic: Aromaticity, Hückel’s Rule Section: 14.7 and 14.9 Difficulty Level: Medium

124) Which compound would you NOT expect to be aromatic?

N

I

S

N

O

H

II

III

B R

IV

V

a) I b) II c) III d) IV e) V Answer: E Topic: Aromaticity, Huckel’s Rule Section: 14.7 and 14.9 Difficulty Level: Medium

125) Which compound would you NOT expect to be aromatic?

53

a) I b) II c) III d) IV e) V Answer: E Topic: Aromaticity, Huckel’s Rule Section: 14.7 and 14.9 Difficulty Level: Medium

126) Which compound would you NOT expect to be aromatic?

N

I

S

N

O

H

II

III

IV

V

a) I b) II c) III d) IV e) V Answer: E Topic: Aromaticity, Hückel’s Rule Section: 14.7 and 14.9 Difficulty Level: Medium

127) Which of these species is aromatic?

54

O

O

N H

O

N H

O

S

I

II

III

IV

V

a) I b) II c) III d) IV e) V Answer: B Topic: Aromaticity, Huckel’s Rule Section: 14.7 and 14.9 Difficulty Level: Medium 128) In which case is the indicated unshared pair of electrons NOT a contributor to the π aromatic system?

N H

I

O

N

II

H

III

IV

a) I b) II c) III d) IV e) None of these choices. Answer: B Topic: Aromaticity, Hückel’s Rule Section: 14.7 and 14.9 Difficulty Level: Medium 129) In which case is the indicated unshared pair of electrons NOT a contributor to the π aromatic system?

55

S

O

N I

H

II

III

IV

a) I b) II c) III d) IV e) None of these choices. Answer: B Topic: Aromaticity, Hückel’s Rule Section: 14.7 and 14.9 Difficulty Level: Medium

130) Which of these species is aromatic? O O

O

O

S

IV

V

N H

O

N H

I

II

III

a) I b) II c) III d) IV e) V Answer: B Topic: Aromaticity, Hückel’s Rule Section: 14.7 and 14.9 Difficulty Level: Hard

131) Which of these species is aromatic?

56

O

N H

I

O

O

N H

O

S

IV

V

III

II

a) I b) II c) III d) IV e) V Answer: B Topic: Aromaticity, Hückel’s Rule Section: 14.7 and 14.9 Difficulty Level: Hard

132) Which of these species is aromatic? O O

O

O

S

IV

V

N H

S

N H

I

II

III

a) I b) II c) III d) IV e) V Answer: B Topic: Aromaticity, Hückel’s Rule Section: 14.7 and 14.9 Difficulty Level: Hard

133) Which of these species is aromatic? 57

N H

N H

I

II

O

O

O

N H

O

S

IV

V

III

a) I b) II c) III d) IV e) V Answer: B Topic: Aromaticity, Hückel’s Rule Section: 14.7 and 14.9 Difficulty Level: Hard

134) Which of these species is aromatic? NH2 O

O N

N H

S

N H

I

II

III

O

N H

IV

V

O

a) I b) II c) III d) IV e) V Answer: E Topic: Aromaticity, Hückel’s Rule Section: 14.7 and 14.9 Difficulty Level: Hard

135) Which of the following would you expect to be antiaromatic?

58

O

I

III

II

IV

V

a) I b) II c) III d) IV e) V Answer: C Topic: Aromaticity, Hückel’s Rule Section: 14.7 and 14.8 Difficulty Level: Hard

136) Which of the following would you expect to be antiaromatic? O

I

II

IV

III

a) I b) II c) III d) IV e) V Answer: C Topic: Aromaticity, Hückel’s Rule Section: 14.7 and 14.8 Difficulty Level: Hard

137) Which of the following would you expect to be antiaromatic?

59

V

O

I

II

III

IV

a) I b) II c) III d) IV e) V Answer: C Topic: Aromaticity, Hückel’s Rule Section: 14.7 and 14.8 Difficulty Level: Hard

138) Which annulene would you NOT expect to be aromatic? a) [6]-Annulene b) [14]-Annulene c) [16]-Annulene d) [18]-Annulene e) [22]-Annulene Answer: C Topic: Aromaticity, Hückel’s Rule Section: 14.7 and 14.8 Difficulty Level: Hard

139) Which of these is an aromatic molecule?

60

V

O

N

O

CH3

CH3

I

B

II

III

N

S

H

O

IV

V

a) I b) II c) III d) IV e) V Answer: A Topic: Aromaticity, Hückel’s Rule Section: 14.7 Difficulty Level: Hard

140) On the basis of molecular orbital theory and Hückel’s rule, which of these compounds should be aromatic?

O

H H

I

II

III

IV

V

a) I b) II c) III d) IV e) V Answer: E Topic: Aromaticity, Hückel’s Rule Section: 14.7 Difficulty Level: Hard

61

141) How many equivalent resonance structures can be written for the cyclopentadienyl anion? a) 3 b) 4 c) 5 d) 6 e) 7 Answer: C Topic: Resonance Forms Section: 14.7 Difficulty Level: Medium

142) How many equivalent resonance structures can be written for the cycloheptatrienyl cation? a) 3 b) 4 c) 5 d) 6 e) 7 Answer: E Topic: Resonance Forms Section: 14.7 Difficulty Level: Medium

143) How many equivalent resonance structures can be written for the cyclopropenyl cation? a) 1 b) 2 c) 3 d) 4 e) 5 Answer: C Topic: Resonance Forms Section: 14.7 Difficulty Level: Medium

144) How many equivalent resonance structures can be written for the cyclobutadienyl dication? 62

a) 1 b) 2 c) 3 d) 4 e) No equivalent resonance forms can be drawn. Answer: D Topic: Resonance Forms Section: 14.7 Difficulty Level: Medium

145) How many resonances would be expected in the broad-band decoupled C-13 spectra of:

a) 1 b) 2 c) 3 d) 4 e) 5 Answer: D Topic: Spectroscopy Section: 14.11 Difficulty Level: Medium

146) How many resonances would be expected in the broad-band decoupled C-13 spectra of:

a) 1 b) 2 c) 3 d) 4 63

e) 5 Answer: C Topic: Spectroscopy Section: 14.11 Difficulty Level: Medium

147) How many resonances would be expected in the broad-band decoupled C-13 spectra of:

a) 1 b) 2 c) 3 d) 4 e) 5 Answer: E Topic: Spectroscopy Section: 14.11 Difficulty Level: Medium

148) How many resonances would be expected in the broad-band decoupled C-13 spectra of:

a) 2 b) 3 c) 4 d) 5 e) 6 Answer: E Topic: Spectroscopy 64

Section: 14.11 Difficulty Level: Medium

149) How many resonances would be expected in the broad-band decoupled C-13 spectra of: CHO

Cl

a) 2 b) 3 c) 4 d) 5 e) 6 Answer: D Topic: Spectroscopy Section: 14.11 Difficulty Level: Medium

150) How many resonances would be expected in the broad-band decoupled C-13 spectra of:

a) 3 b) 4 c) 5 d) 6 e) 7 Answer: E Topic: Spectroscopy Section: 14.11 Difficulty Level: Medium 65

151) How many resonances would be expected in the broad-band decoupled C-13 spectra of:

a) 2 b) 3 c) 4 d) 5 e) 6 Answer: B Topic: Spectroscopy Section: 14.11 Difficulty Level: Medium

152) How many resonances would be expected in the broad-band decoupled C-13 spectra of:

a) 4 b) 5 c) 6 d) 7 e) 8 Answer: E Topic: Spectroscopy Section: 14.11 Difficulty Level: Medium

153) How many resonances would be expected in the broad-band decoupled C-13 spectra of: 66

a) 4 b) 5 c) 6 d) 7 e) 8 Answer: A Topic: Spectroscopy Section: 14.11 Difficulty Level: Medium

154) How many resonances would be expected in the broad-band decoupled C-13 spectra of:

a) 4 b) 5 c) 6 d) 7 e) 8 Answer: E Topic: Spectroscopy Section: 14.11 Difficulty Level: Medium

155) How many resonances would be expected in the broad-band decoupled C-13 spectra of:

a) 4 67

b) 5 c) 6 d) 7 e) 8 Answer: B Topic: Spectroscopy Section: 14.11 Difficulty Level: Medium

156) How many resonances would be expected in the broad-band decoupled C-13 spectra of:

a) 5 b) 6 c) 7 d) 8 e) 9 Answer: E Topic: Spectroscopy Section: 14.11 Difficulty Level: Medium

157) How many resonances would be expected in the broad-band decoupled C-13 spectra of:

a) 4 b) 5 c) 6 d) 7 e) 8 68

Answer: E Topic: Spectroscopy Section: 14.11 Difficulty Level: Medium

158) Which of these compounds absorbs at the longest wavelength in the UV-visible region?

I

II

III

IV

V

a) I b) II c) III d) IV e) V Answer: B Topic: Spectroscopy Section: 14.11 Difficulty Level: Medium 159) A compound has the formula C8H9Br. Its 1H NMR spectrum consists of: doublet, δ 2.0 quartet, δ 5.15 multiplet, δ 7.35 The IR spectrum shows two peaks in the 680-840 cm-1 region; one is between 690 and 710 cm-1 and the other is between 730 and 770 cm-1. Which is a possible structure for the compound? Br

Br

Br

II

I

III

Br

Br

IV

V

a) I b) II 69

c) III d) IV e) V Answer: D Topic: Spectroscopy Section: 14.11 Difficulty Level: Medium 160) Which of the following substances, formula C8H9Br, might exhibit the following 1H NMR spectrum? triplet, δ 2.8 triplet, δ 4.65 multiplet, δ 7.2 Br

Br

Br

II

I

III

Br

Br

IV

V

a) I b) II c) III d) IV e) V Answer: C Topic: Spectroscopy Section: 14.11 Difficulty Level: Medium 161) Which of the following substances, formula C8H9Br, might exhibit the following 1H NMR spectrum? triplet, δ 1.2 quartet, δ 2.45 multiplet, δ 7.4

70

Br

Br

Br

II

I

III

Br

Br

V

IV a) I b) II c) III d) IV e) V Answer: A Topic: Spectroscopy Section: 14.11 Difficulty Level: Medium

162) Which of the following substances, formula C8H9Br, might exhibit the following 1H NMR spectrum? singlet, δ 2.45 singlet, δ 2.5 multiplet, δ 7.35 Br

Br

Br

II

I

III

Br

Br

IV

V

a) I b) II c) III d) IV e) V Answer: E 71

Topic: Spectroscopy Section: 14.11 Difficulty Level: Medium 163) Which of the following substances, C8H9Cl, would exhibit five signals in its 13C NMR spectrum? Cl Cl

Cl

I

III

II Cl

Cl

V

IV

a) I b) II c) III d) IV e) V Answer: C Topic: Spectroscopy Section: 14.11 Difficulty Level: Medium 164) Which of the following substances, C9H10O, would exhibit seven signals in its 13C NMR spectrum? O O

I

O

II

III

HO

O

IV

V

a) I b) II

72

c) III d) IV e) V Answer: A Topic: Spectroscopy Section: 14.11 Difficulty Level: Medium 165) For which of the following substances, C9H10O, would the aromatic multiplet, in its 1H NMR spectrum, consist of two doublets? O O

I

O

II

III

HO

O

IV

V

a) I b) II c) III d) IV e) V Answer: A Topic: Spectroscopy Section: 14.11 Difficulty Level: Medium 166) In the 1H NMR spectra of which of the following substances, C9H10O, would you expect to see two singlets in the range of δ 2.0-2.5 ppm?

73

O O O

I

II

III

HO

O

V

IV

a) I and III b) I, II, and III c) IV d) V e) All of these substances would exhibit two singlets δ 2.0-2.5 ppm in their 1H NMR spectra. Answer: B Topic: Spectroscopy Section: 14.11 Difficulty Level: Medium 167) Which isomer of C7H7Cl exhibits strong IR absorbances at 690 and 750 cm1? CH3

CH3

CH3

CH2Cl

Cl Cl Cl

I a) I b) II c) III d) IV e) II and IV

II

III

IV

Answer: E Topic: Spectroscopy Section: 14.11 Difficulty Level: Hard

168) Which reagent(s)/technique would serve to distinguish between azulene and bicyclo[5.3.0]decane? 74

a) Br2, CCl4 b) KMnO4, OH−, H2O c) NMR Spectroscopy d) UV Spectroscopy e) Two of these choices. Answer: E Topic: Chemical and Spectroscopic Analysis Section: 13.9, 14.7 and 14.11 Difficulty Level: Medium

169) Which reagent(s)/technique would serve to distinguish between azulene and bicyclo[5.3.0]decane?

a) Br2, CCl4 b) KMnO4, OH−, H2O c) NMR Spectroscopy d) NaBH4, H2O e) Two of these choices. Answer: C Topic: Chemical and Spectroscopic Analysis Section: 14.7 and 14.11 Difficulty Level: Medium

Question type: fill-in-the-blank

170) A compound that reacts like an alkane, alkene, alkyne, or one of their derivatives, is called an ___ compound, while one that reacts like benzene is called an ___ compound. Answer: aliphatic, aromatic Topic: General Concepts Section: 14.1 Difficulty Level: Easy 75

171) Humans do not have the biochemical ability to synthesize the benzene ring. Therefore, two amino acids, ___ and ___, are essential to the human diet. Answer: tryptophan, phenylalanine Topic: General Concepts Section: 14.10 Difficulty Level: Easy

172) Cagelike molecules with the geometry of a truncated icosahedron are called ___. Answer: fullerenes Topic: General Concepts Section: 14.8 Difficulty Level: Easy

173) Monocyclic compounds with alternating single and double bonds are called ___. Answer: annulenes Topic: General Concepts Section: 14.7 Difficulty Level: Easy

174) The difference between the amount of heat actually released upon hydrogenation of benzene and that calculated on the basis of the Kekule structure is called the ___ of benzene. Answer: resonance energy Topic: General Concepts Section: 14.5 Difficulty Level: Easy

175) Molecular orbitals of equal energy are referred to as ___ orbitals. Answer: degenerate Topic: General Concepts Section: 14.6 76

Difficulty Level: Medium

176) When a benzene ring is used as a substituent, it is called a ___ group. Answer: phenyl Topic: Nomenclature Section: 14.2 Difficulty Level: Easy

Question type: Molecular Drawing

177) Draw the structure corresponding to the following name: 2-bromo-5-nitrophenol OH Br

Answer: O2N Topic: Nomenclature Section: 14.2 Difficulty Level: Medium

178) Draw the structure corresponding to the following name: 3-bromo 5-phenylaniline NH2

Br

Answer: Topic: Nomenclature Section: 14.2 Difficulty Level: Medium

179) Draw the structure corresponding to the following name: 3-nitro-4-iodoanisole O2N

Answer:

O

I

77

Topic: Nomenclature Section: 14.2 Difficulty Level: Medium

Question type: Essay

180) Give the IUPAC name for the following substance: OH O

Answer: 2-methyl-4-(3-methylbutyl)benzoic acid Topic: Nomenclature Section: 14.2 Difficulty Level: Hard

181) Draw the structure corresponding to the following name: 2-hydroxy-4-(3methylcyclopentyl)benzoic acid HO

Answer:

HO2C

Topic: Nomenclature Section: 14.2 Difficulty Level: Hard

Question type: fill-in-the-blank 182) Hückel’s Rule requires ___ π electrons for an aromatic compound. Answer: 4n+2 Topic: Hückel’s rule Section: 14.7 Difficulty Level: Easy

Question type: Essay 78

183) The heats of hydrogenation for cyclohexene and benzene are given below. Calculate the resonance stabilization energy of benzene. C6H10 + H2 Æ C6H12 C6H6 + 3H2 Æ C6H12

ΔHo = -120 kJ/mol ΔHo = -208 kJ/mol

Answer: The resonance stabilization energy of benzene is the difference between the theoretical and observed ΔHo values. Hydrogenation of three double bonds should release 3 times the energy released when one double bond is hydrogenated. Thus, the theoretical ΔHo for benzene can be calculated as [3x (120)] kJ/mol = -360 kJ/mol Therefore, Resonance stabilization energy of benzene = (-208) – (-360) kJ/mol = 152 kJ/mol Topic: Aromaticity, Resonance Stabilization Energy Section: 14.5 Difficulty Level: Medium

184) Use the “polygon-in-circle” method to draw an MO diagram showing the pi-electron distribution pattern in the cyclopentadienyl anion. How is this diagram useful in explaining the aromatic properties of this anion? Answer: The following MO diagram can be generated using the polygon-in-circle method. The six pi electrons of the cyclopentadienyl anion in the bonding molecular orbitals form a closed bonding shell, accounting for its aromatic properties.

Antibonding MO Bonding MO 6 pi electrons "closed bonding shell" Topic: Aromaticity, Molecular Orbital Theory Section: 14.7 Difficulty Level: Medium

185) Use the “polygon-in-circle” method to draw an MO diagram showing the pi-electron distribution pattern in the cyclopentadienyl cation. How is this diagram useful in explaining the antiaromatic properties of this anion?

79

Answer: This MO diagram can be generated using the polygon-in-circle method. The 4 pi electrons of the cyclopentadienyl cation in the bonding molecular orbitals form a bonding shell which lacks 2 pi electrons from being closed, accounting for its antiaromatic properties. Topic: Aromaticity, Molecular Orbital T heory Section: 14.7 Difficulty Level: Medium

186) Use the “polygon-in-circle” method to draw an MO diagram showing the pi-electron distribution pattern in the cycloheptatrienyl cation. How is this diagram useful in explaining the antiaromatic properties of this anion?

Answer: This MO diagram can be generated using the polygon-in-circle method. The six pi electrons of the cycloheptatrienyl cation in the bonding molecular orbitals form a closed bonding shell, accounting for its aromatic properties Topic: Aromaticity, Molecular Orbital Theory Section: 14.7 Difficulty Level: Medium

187) The pka of cyclopentadiene is found to be 16 while, by contrast, that of cycloheptatriene is found to be 36. Explain the large difference found in the two pka values.

H

H

..

Answer: The 20 order of magnitude difference in acidity of cyclopentadiene compared with cycloheptatriene lies in the fact that the conjugate base of cyclopentadiene is the aromatic cyclopentadienyl anion, a very stable conjugate base species. However, in the case of cycloheptatriene, removal of a proton produces the cyclohe[tatrienyl anion, a cyclic, conjugated, planar system with 8 π-electrons, that is antiaromatic. B:− H

Aromatic anion

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H

H

H

B:-

Topic: Aromaticity, Molecular Orbital Theory Section: 14.7 Difficulty Level: Hard

188) Benzene, while unusually unreactive with electrophiles, will react under certain conditions. However, when it does react, it does so by ___ rather than by addition. Answer: substitution Topic: Aromaticity, Reactivity Section: 14.3 Difficulty Level: Easy

189) Explain briefly why cyclopentadiene readily reacts with strong bases.

H

H

..

Answer: The acidity of a substance can be often be correlated with the stability of its conjugate base: substances that have exceptionally stable conjugate bases tend to be strong acids. The conjugate base of cyclopentadiene, formed during reaction with a base, is exceptionally stable, by virtue of being an aromatic anion (6 pi electrons, planar ring), thus accounting for the readiness with which cyclopentadiene reacts with bases. B:− H

Aromatic anion

Topic: Aromaticity, Reactivity Section: 14.7 Difficulty Level: Medium

190) Cyclohepatriene is found to readily undergo a hydride transfer with triphenylmethyl arbocation to generate the cycloheptatrienyl cation and triphenylmethane. Explain why this transformation is facile.

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H

H

H

+

Ph3C+

+

Ph3CH

Answer: This reaction readily proceeds because the product, cycloheptatrienyl cation, is aromatic and much more stable than even the triphenyl substituted carbocation. Topic: Aromaticity, Reactivity Section: 14.7 Difficulty Level: Medium

191) Pyrrole is not particularly basic, because the lone pair on the nitrogen is ___. Answer: part of the aromatic system Topic: Aromaticity, Reactivity Section: 14.9 Difficulty Level: Medium

192) The Lewis structures of both pyridine and pyrrole have an electron pair on the nitrogen atom, suggesting that both substances might possess basic properties. However, only pyridine reacts readily with HCl to form pyridinium chloride, while pyrrole is rather unreactive. Explain clearly, using relevant diagrams to illustrate/clarify your answer. Answer: + HCl N

..

N+ − Cl H

2

sp pyridinium chloride

pyridinium chloride

.. p N H

+ HCl

X

H N + Cl− H

not aromatic pyrrole electron pair: part of aromatic pi sextet Both pyridine and pyrrole are known to exhibit aromatic properties; the nitrogen atom must therefore be sp2 hybridized in both cases. In the pyridine molecule, this places the electron pair in an sp2 hybrid orbital, and not involved in the aromatic π sextet needed for aromatic stability; the electron pair is thus “available” for

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reacting with HCl, forming pyridinium chloride, while preserving aromatic stability. By contrast, the electron pair in pyrrole must be placed in the p orbital, since all three sp2 orbitals are used in sigma bonds with neighboring atoms. This allows the electron pair to contribute to aromatic stability by becoming part of the aromatic sextet. Thus, the electron pair on nitrogen is not “available” for reacting with HCl, because doing so would destroy the aromaticity of the ring. Topic: Aromaticity, Reactivity Section: 14.9 Difficulty Level: Medium

193) Predict the product of the reaction of one equivalent of hydrochloric acid with the organic compound shown: H N

1 equivalent HCl

N

Answer: H N

H N

1 equivalent HCl

N

N

H

Topic: Aromaticity, Reactivity Section: 14.9 Difficulty Level: Medium

194) Consider the nitrogen atom in the molecules of pyrrole and pyrrolidine. Bearing in mind that pyrrole exhibits aromatic properties, compare the hybridization of nitrogen in both species, explaining why it must be different, although at first glance, it may appear identical. H N

pyrrole

H N

pyrrolidine

Answer:

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sp2 NH

sp3 NH

In pyrrole, the conjugated unsaturated ring system forces the nitrogen to be trigonal planar, that is sp2 hybridized, with the lone pair electrons in an unhybridized p-orbital. This allows for overlap with the conjugate system accounting for the aromatic character. The nitrogen in pyrrolidine, on the other hand, is closer to tetrahedral, and as a result sp3 hybridized, and the lone pair electrons reside in an sp3 hybrid orbital. Topic: Aromaticity, Reactivity Section: 14.9 Difficulty Level: Medium

195) Briefly explain why the aromatic hydrocarbon shown possesses a significant dipole moment. Use diagrams as needed to illustrate/clarify your answer.

Answer:

+ =

The stable, low energy resonance contributor shown creates an aromatic system in both rings. This separation of charge creates the significant dipole observed. Topic: Aromaticity Section: 14.7 Difficulty Level: Hard

196) Briefly explain why the aromatic hydrocarbon shown possesses a significant dipole moment. Use diagrams as needed to illustrate/clarify your answer.

84

Answer:

The stable, low energy resonance contributor shown creates an aromatic system in both rings. This separation of charge creates the significant dipole observed. Topic: Aromaticity Section: 14.7 and 14.8 Difficulty Level: Hard

197) Briefly explain why the aromatic hydrocarbon azulene, C10H8, possesses a significant dipole moment. Use diagrams as needed to illustrate/clarify your answer. Answer: Azulene has the bicyclic structure shown below. Since the “non-polar” resonance hybrid meets the Hückel rule for aromaticity, it accounts for the observed aromatic properties of azulene. However, closer scrutiny suggests that a shift in electron density, in which the 7membered ring is electron deficient and the 5-membered ring is electron-rich would be especially stable: each ring is now independently aromatic, an aromatic cycloheptatrienyl cation fused with an aromatic cyclopentadienyl anion. Thus, the most stable pi-electron distribution would suggest a polar structure for azulene, accounting for this substance having a significant dipole moment.

non-polar

polar

Topic: Aromaticity Section: 14.7 Difficulty Level: Hard

198) Although all bond lengths in benzene are identical, that is not always true for all aromatic compounds. In naphthalene, for instance, the C1-C2 bond is shorter than the C2-C3 bond. Explain, using resonance theory. 85

Answer: The major resonance structures for naphthalene are drawn below. The observed bond lengths reflect the contribution of each structure to the overall resonance hybrid: The C1-C2 bond: two double bonds (I and II), and one single bond (III) The C2-C3 bond: one double bond (III), and two single bonds (I and II) Overall: C1-C2 bond is more double-bond-like, thus shorter.

shorter 1

1

1

1

2

2

2

2

3

3

3

3

II

I

III

longer

IV

Topic: Resonance, Bond Lengths, Bond Order Section: 14.7 Difficulty Level: Medium

Question type: Molecular Drawing

199) Draw all significant resonance structures for pyridine, C6H5N

Answer:

..N

N ..

Topic: Resonance Section: 1.8 and 14.9 Difficulty Level: Hard

200) Draw all significant resonance structures for azulene, C10H8

Answer: Topic: Resonance Section: 1.8 and 14.8 Difficulty Level: Hard

201) Draw all significant resonance structures for the cyclopentadienyl anion. Answer: 86

202) Consider the oxygen atom in the molecules of furan and tetrahydrofuran. Bearing in mind that furan exhibits aromatic properties, compare the hybridization of oxygen in both species, explaining why it must be different, although at first glance, it may appear identical. .. .. O. O.. .

Furan

THF

Answer: .. p

3 .. sp

2 O .. sp

Furan: sp2 hybridized one electron pair in p orbital: part of aromatic pi sextet

O

.. sp3

Tetrahydrofuran: sp3 hybridized both electron pairs in sp3 orbitals

Oxygen has 2 lone electron pairs in both species and, at first glance, it might appear that the hybridization patterns are identical. In THF, the oxygen atom is sp3 hybridized and both pairs can be placed in sp3 hybrid orbitals. In furan, there are two possibilities that must be considered: i) the oxygen may be sp3 hybridized, with both electron pairs sp3 hybrid orbitals, as in THF, or, ii) oxygen may be sp2 hybridized, with one electron pair in an sp3 hybrid orbital, the other in a p orbital. In the latter case, the electrons in the p orbital can then become part of an aromatic sextet, allowing the molecule to gain aromatic stability. Since furan is known to exhibit markedly aromatic properties, the oxygen must be sp2 hybridized. Topic: Resonance Section: 1.8 and 14.8 Difficulty Level: Hard

203) The compound illustrated below is found to have the following signals in its broadband decoupled C-13 spectra: 190.77, 140.91, 134.82, 130.89 and 129.45 δ Using resonance theory, assign the C-13 peaks to the appropriate carbons.

87

CHO

Cl

Answer: 190.77 CHO 134.82 130.89 129.45 140.91 Cl

Topic: Spectroscopy and Resonance Theory Section: 14.11 Difficulty Level: Medium

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