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Essential Organic Chemistry 2nd Edition Bruice

Essential Organic Chemistry, 2e (Bruice)

 

Chapter 6

 

 

Isomers and Stereochemistry

 

1)

 

Write two of the constitutional isomers for C3H8O.

 

Answer:

 

CH3CH2CH2OH and CH3CH2OCH3

 

Section:

 

 

6.0

 

2)

 

Draw the cis and trans isomers for 2-hexene.

 

Answer:

 

 

 

 

Section:

 

 

6.1

 

3)

 

Draw the cis and trans isomers for 1-bromo-2-methylcyclopropane.

 

Answer:

 

 

trans                                                                       cis

 

Section:

 

 

6.1

 

4)

 

What is the IUPAC name of the following structure?

 

 

 

Answer:

 

trans-1-isobutyl-3-methylcyclobutane

 

Section:

 

 

6.1

 

5)

 

What is the IUPAC name of the following structure?

 

 

Answer:

 

trans-2,5-dimethyl-3-hexene

 

Section:

 

 

6.1

 

6)

 

Explain how to determine if an object or molecule is chiral.

 

Answer:

 

If an object’s or molecule’s mirror image will not superimpose on the original object or molecule, then the object or molecule is chiral.

 

Section:

 

 

6.2

 

7)

 

Which of the following objects are achiral?

 

  1. A)

 

fork

 

  1. B)

 

balloon with no drawing on it

 

  1. C)

 

a hand

 

  1. D)

 

A and B

 

  1. E)

 

B and C

 

Answer:

 

D

 

Section:

 

 

6.2

 

8)

 

Which of the following compounds is never chiral?

 

  1. A)

 

2,3-dibromobutane

 

  1. B)

 

1,3-dibromobutane

 

  1. C)

 

1,2-dichlorobutane

 

  1. D)

 

1,4-dibromobutane

 

  1. E)

 

1-bromo-2-chlorobutane

 

Answer:

 

D

 

Section:

 

 

6.2

 

9)

 

Is the molecule shown below chiral or achiral?

 

 

 

Answer:

 

achiral

 

Section:

 

 

6.2

 

10)

 

Is the molecule shown below chiral or achiral?

 

 

 

Answer:

 

chiral

 

Section:

 

 

6.2

 

11)

 

Is the molecule shown below chiral or achiral?

 

 

 

Answer:

 

achiral

 

Section:

 

 

6.2

 

12)

 

Which of the following compounds has an asymmetric center?

 

 

  1. A)

 

I

 

  1. B)

 

II

 

  1. C)

 

III

 

  1. D)

 

IV

 

  1. E)

 

V

 

Answer:

 

C

 

Section:

 

 

6.3

 

13)

 

Mark each asymmetric center in the following molecule with an asterisk.

 

 

 

Answer:

 

 

 

 

Section:

 

 

6.3

 

14)

 

Mark each asymmetric center in the following molecule with an asterisk.

 

 

 

Answer:

 

 

 

 

Section:

 

 

6.3

 

15)

 

How many asymmetric centers are present in the compound below?

 

 

 

Answer:

 

5

 

Section:

 

 

6.3

 

16)

 

How many asymmetric centers are present in a molecule of 2,4,6-trimethylheptane?

 

  1. A)

 

0

 

  1. B)

 

1

 

  1. C)

 

2

 

  1. D)

 

3

 

  1. E)

 

4

 

Answer:

 

A

 

Section:

 

 

6.3

 

17)

 

A and B are stereoisomers. They are nonsuperimposable and are mirror images of one another. Which of the following best describes the relationship between A and B?

 

  1. A)

 

structural isomers

 

  1. B)

 

enantiomers

 

  1. C)

 

cis-trans isomers

 

  1. D)

 

diastereomers

 

  1. E)

 

constitutional isomers

 

Answer:

 

B

 

Section:

 

 

6.4

 

18)

 

Which of the following compounds is an enantiomer of the structure below?

 

 

 

  1. A)

 

 

 

 

  1. B)

 

 

 

 

  1. C)

 

 

 

 

  1. D)

 

A and B

 

  1. E)

 

It does not have an enantiomer.

 

Answer:

 

E

 

Section:

 

 

6.4

 

19)

 

Which of the following compounds is chiral?

 

  1. A)

 

 

 

 

  1. B)

 

 

 

 

  1. C)

 

 

 

 

  1. D)

 

 

 

 

Answer:

 

B

 

Section:

 

 

6.2 and 6.4

 

20)

 

Is the molecule shown below chiral or achiral?

 

 

 

Answer:

 

achiral

 

Section:

 

 

6.2 and 6.4

 

21)

 

Which of the following terms best describes the pair of compounds shown:  enantiomers, diastereomers, or the same compound?

 

 

 

Answer:

 

the same compound

 

Section:

 

 

6..4, 6.5, and 6.9

 

22)

 

Which of the following statements correctly describes the molecule shown below?

 

 

 

  1. A)

 

It is achiral.

 

  1. B)

 

It is meso.

 

  1. C)

 

Its asymmetric center possesses the R configuration.

 

  1. D)

 

The mirror image of this molecule is its enantiomer.

 

  1. E)

 

The molecule possesses enantiotopic hydrogens.

 

Answer:

 

D

 

Section:

 

 

6.4

 

23)

 

Assign relative priorities to the following groups (Use 1  for the highest priority and 4 for the lowest priority).

 

 

 

Answer:

 

 

 

 

Section:

 

 

6.6

 

24)

 

Which of the following compounds has an S configuration?

 

  1. A)

 

 

 

 

  1. B)

 

 

 

 

  1. C)

 

 

 

 

  1. D)

 

 

 

 

  1. E)

 

 

 

 

Answer:

 

B

 

Section:

 

 

6.6

 

25)

 

Which of the following groups has the highest priority when ranking the groups or atoms bonded to the asymmetric center?

 

  1. A)

 

 

 

 

  1. B)

 

 

 

 

  1. C)

 

OH

 

  1. D)

 

OCH3

 

  1. E)

 

 

 

 

Answer:

 

D

 

Section:

 

 

6.6

 

26)

 

The configuration of R-(+)-glyceraldehyde is as follows:

 

What is the absolute configuration of (-)-lactic acid?

 

 

  1. A)

 

R configuration

 

  1. B)

 

L configuration

 

  1. C)

 

S configuration

 

  1. D)

 

R and S configuration

 

  1. E)

 

D and L configuration

 

Answer:

 

A

 

Section:

 

 

6.6

 

27)

 

Assign priorities to each group/element on both compounds, assign R or S configuration to each structure and explain the relationship between the two structures?

assign priorities to each group.

 

Answer:

 

 

 

Therefore, the two compounds are enantiomers.

 

Section:

 

 

6.6

 

28)

 

Label each chiral carbon in the compound below as R or S.

 

 

 

Answer:

 

 

 

 

Section:

 

 

6.6

 

29)

 

Draw the structure of (S)-1-bromo-1-chloropropane. Use solid-wedge lines and dashed lines  in the structure to show the stereochemistry around the asymmetric center.

 

Answer:

 

 

 

 

Section:

 

 

6.6

 

30)

 

Provide the structure of (R)-4-octanol.  Be careful to indicate the proper stereochemistry.

 

Answer:

 

 

 

 

Section:

 

 

6.6

 

31)

 

Which of the following is not true of enantiomers?

 

  1. A)

 

They have the same melting point.

 

  1. B)

 

They have the same boiling point.

 

  1. C)

 

They have the same chemical reactivity with non-chiral reagents.

 

  1. D)

 

They have the same density.

 

  1. E)

 

They have the same specific rotation.

 

Answer:

 

E

 

Section:

 

 

6.7

 

32)

 

Which of the following is/are optically inactive?

 

  1. A)

 

a 50-50 mixture of R and S enantiomers

 

  1. B)

 

a meso compound

 

  1. C)

 

every achiral compound

 

  1. D)

 

a racemic mixture

 

  1. E)

 

all the above

 

Answer:

 

E

 

Section:

 

 

6.7

 

33)

 

Which of the following statements is correct concerning a pair of enantiomers?

 

  1. A)

 

They rotate the plane of polarized light by exactly the same amount and in opposite directions.

 

  1. B)

 

They rotate the plane of polarized light by differing amounts and in opposite directions.

 

  1. C)

 

They rotate the plane of polarized light by differing amounts and in the same direction.

 

  1. D)

 

They have different melting points.

 

  1. E)

 

They have the same melting point, but they have different boiling points.

 

Answer:

 

A

 

Section:

 

 

6.7

 

34)

 

A mixture of equal amounts of two enantiomers __________.

 

  1. A)

 

is called a racemic mixture

 

  1. B)

 

is optically inactive

 

  1. C)

 

implies that the enantiomers are meso forms

 

  1. D)

 

both A and B

 

  1. E)

 

none of the above

 

Answer:

 

D

 

Section:

 

 

6.7

 

35)

 

Which of the following is a true statement?

 

  1. A)

 

All chiral molecules possess a plane of symmetry.

 

  1. B)

 

All achiral molecules are meso.

 

  1. C)

 

All molecules which possess a single asymmetric center of the S configuration are levorotatory.

 

  1. D)

 

A mixture of achiral compounds will be optically inactive.

 

  1. E)

 

All molecules which possess 2 or more chirality centers will be chiral.

 

Answer:

 

D

 

Section:

 

 

6.7

 

36)

 

Explain the difference between dextrorotatory and levorotatory.

 

Answer:

 

Dextrorotatory  means an optically active compound that rotates a plane of polarized light clockwise and levorotatory means an optically active compound that rotates a plane of polarized light counterclockwise.

 

Section:

 

 

6.7

 

37)

 

A solution containing 0.96 g of 2-bromooctane in 10ml ether solution gave an observed rotation of -1.8° in a 10 cm cell at 20°C. Calculate the specific rotation of this solution.

 

Answer:

 

=

 

=  = -18.75° in ether

 

Section:

 

 

6.8

 

38)

 

If (S)-glyceraldehyde has a specific rotation of -8.7°, what is the specific rotation of (R)-glyceraldehyde?

 

  1. A)

 

-8.7°

 

  1. B)

 

+8.7°

 

  1. C)

 

0.0°

 

  1. D)

 

cannot be determined from the information given

 

Answer:

 

B

 

Section:

 

 

6.8

 

39)

 

A newly isolated natural product was shown to be optically active. If a solution of 2.0 g in 10 mL of ethanol in a 50 cm tube gives a rotation of +2.57°, what is the specific rotation of this natural product?

 

Answer:

 

+2.57°

 

Section:

 

 

6.8

 

40)

 

Which of the statements is correct about diastereomers?

 

  1. A)

 

They are stereoisomers that are not enantiomers.

 

  1. B)

 

They are a pair of identical isomers.

 

  1. C)

 

They are a pair of isomers that are mirror images.

 

  1. D)

 

All their asymmetric centers are the same.

 

Answer:

 

A

 

Section:

 

 

6.9

 

41)

 

What is the relationship between the following compounds?

 

 

 

  1. A)

 

enantiomers

 

  1. B)

 

diastereomers

 

  1. C)

 

constitutional isomers

 

  1. D)

 

conformational isomers

 

  1. E)

 

identical compounds

 

Answer:

 

A

 

Section:

 

 

6.9

 

42)

 

What is the relationship between the following compounds?

 

 

 

  1. A)

 

enantiomers

 

  1. B)

 

diastereomers

 

  1. C)

 

constitutional isomers

 

  1. D)

 

conformational isomers

 

  1. E)

 

identical compounds

 

Answer:

 

B

 

Section:

 

 

6.9

 

43)

 

Draw the structure of (2R,3S)-dichloropentane. Take particular care to indicate three-dimensional stereochemical detail properly.

 

Answer:

 

 

 

 

Section:

 

 

6.6 and 6.9

 

44)

 

Draw the structure of (2S,3R)-dichloropentane. Take particular care to indicate three-dimensional stereochemical detail properly.

 

Answer:

 

 

 

 

Section:

 

 

6.6 and 6.9

 

45)

 

Draw the structure of any diastereomer of (2R,3S)-dichloropentane. Take particular care to indicate three-dimensional stereochemical detail properly.

 

Answer:

 

 

 

 

Section:

 

 

6.6 and 6.9

 

46)

 

Stereoisomers which are not mirror image isomers are __________.

 

Answer:

 

diastereomers

 

Section:

 

 

6.9

 

47)

 

Which of the following terms best describes the pair of compounds shown: enantiomers, diastereomers, or the same compound?

 

 

 

Answer:

 

the same compound

 

Section:

 

 

6.6 and 6.9

 

48)

 

The compound CH3CHClCH2CH=CHCH2CH3 contains only one asymmetric center. Explain why it has four stereoisomers.

 

Answer:

 

In addition to the single asymmetric center which may be either R or S, it also contains a carbon-carbon double bond which may be either E or Z. Thus, the four stereoisomers can be designated E, R; E, S; Z, R; and Z, S.

 

Section:

 

 

6.6 and 6.9

 

49)

 

How many diastereomers exist for the compound below?

 

 

 

  1. A)

 

2

 

  1. B)

 

4

 

  1. C)

 

6

 

  1. D)

 

7

 

  1. E)

 

8

 

Answer:

 

C

 

Section:

 

 

6.9

 

 

 

50)

 

Which of the following is a meso compound?

 

  1. A)

 

 

 

 

  1. B)

 

 

 

 

  1. C)

 

 

 

 

  1. D)

 

 

 

 

  1. E)

 

 

 

 

Answer:

 

A

 

Section:

 

 

6.10

 

51)

 

What is the relationship between the following compounds?

 

 

 

  1. A)

 

enantiomers

 

  1. B)

 

diastereomers

 

  1. C)

 

constitutional isomers

 

  1. D)

 

conformational isomers

 

  1. E)

 

identical compounds

 

Answer:

 

E

 

Section:

 

 

6.10

 

52)

 

Consider the molecule C2H2Br2Cl2.

  1. a) Draw a structure that is optically inactive because it does not have an asymmetric center.
  2. b) Draw a structure that is optically inactive because it is a meso compound.
  3. c) Draw a structure that is optically active because it is chiral.

 

Answer:

 

a)

no chirality center

b)

meso compound

c)

chiral

 

Section:

 

 

6.10

 

53)

 

Which of the statements below correctly describes an achiral molecule?

 

  1. A)

 

The molecule has a nonsuperimposable mirror image.

 

  1. B)

 

The molecule exhibits optical activity when it interacts with plane-polarized light.

 

  1. C)

 

The molecule has an enantiomer.

 

  1. D)

 

The molecule might be a meso form.

 

  1. E)

 

none of the above

 

Answer:

 

D

 

Section:

 

 

6.10

 

54)

 

How many stereoisomers exist with the following basic connectivity?

 

BrCH2CH(CH3)CH2CH3

 

  1. A)

 

0

 

  1. B)

 

1

 

  1. C)

 

2

 

  1. D)

 

4

 

  1. E)

 

8

 

Answer:

 

C

 

Section:

 

 

6.10

 

55)

 

How many stereoisomers exist with the following basic connectivity?

 

CH3CHClCH2CHClCH3

 

  1. A)

 

0

 

  1. B)

 

1

 

  1. C)

 

2

 

  1. D)

 

3

 

  1. E)

 

4

 

Answer:

 

D

 

Section:

 

 

6.10

 

56)

 

What is the configuration of the following compound?

 

 

 

  1. A)

 

2S, 3R

 

  1. B)

 

3R, 3S

 

  1. C)

 

2S, 3S

 

  1. D)

 

2R, 3R

 

  1. E)

 

Can’t do R and S; the compound is achiral.

 

Answer:

 

C

 

Section:

 

 

6.6, 6.9, and 6.10

 

57)

 

Label each chiral carbon in the compound below as R or S.

 

 

 

Answer:

 

 

 

 

Section:

 

 

6.6, 6.9, and 6.10

 

58)

 

Draw a perspective formula of (2R,3S)-3-bromo-2-butanol.

 

Answer:

 

 

 

 

Section:

 

 

6.6, 6.9, and 6.10

 

59)

 

In the Fischer projection below, what are the configurations of the two chirality centers?

 

 

 

  1. A)

 

2R, 3R

 

  1. B)

 

2R, 3S

 

  1. C)

 

2S, 3R

 

  1. D)

 

2S, 3S

 

  1. E)

 

cannot be determined from structure

 

Answer:

 

A

 

Section:

 

 

6.6, 6.9, and 6.10

 

 

 

60)

 

Draw any diastereomer of (2R,3R)-2,3-dichloropentane.  Be careful to indicate proper stereochemistry.

 

Answer:

 

 

 

 

Section:

 

 

6.6, 6.9, and 6.10

 

61)

 

Can one predict whether a compound with a single chiral carbon is dextro- or levorotatory based on the R/S assignment at this chiral carbon? Explain briefly.

 

Answer:

 

No. R/S assignment is purely a convention of nomenclature and is completely independent of the direction in which plane-polarized light is rotated by the compound.

 

Section:

 

 

6.6, 6.9, and 6.10

 

62)

 

Briefly describe how two enantiomers might be separated.

 

Answer:

 

The two compounds can be converted to diastereomers, separated based on different physical properties of these diastereomers, and subsequently returned to their original forms or chromatographic separation using a chiral stationary phase.

 

Section:

 

 

6.11

 

63)

 

A receptor is a protein that binds a particular molecule and is achiral.

 

Answer:

 

FALSE

 

Section:

 

 

6.12

 

64)

 

Explain the term “stereochemistry.”

 

Answer:

 

It is the field of chemistry that deals with the structures of molecules in three dimensions.

 

Section:

 

 

6.13

 

Essential Organic Chemistry, 2e (Bruice)

 

Chapter 7

 

 

Delocalized Electrons and Their Effect on Stability, Reactivity, and pKa: Ultraviolet and Visible Spectroscopy

 

1)

 

Which of the following statements are correct concerning localized electrons?

 

  1. A)

 

Electrons are restricted to a particular region.

 

  1. B)

 

Electrons belong to a single atom.

 

  1. C)

 

Electrons are related to a bond between atoms.

 

  1. D)

 

A, B, and C

 

  1. E)

 

A, and C

 

Answer:

 

D

 

Section:

 

 

7.0

 

2)

 

Which of the following statements are correct concerning delocalized electrons ?

 

  1. A)

 

Electrons do not belong to a single atom.

 

  1. B)

 

Electrons are not confined to a bond between two atoms

 

  1. C)

 

Electrons are shared by three or more atoms.

 

  1. D)

 

A and B

 

  1. E)

 

A, B, and C

 

Answer:

 

E

 

Section:

 

 

7.0

 

3)

 

Which of the following statements are correct concerning benzene?

 

  1. A)

 

Benzene is a planar molecule.

 

  1. B)

 

The six carbon-carbon bonds have the same length.

 

  1. C)

 

Benzene has alternating single and double bonds.

 

  1. D)

 

A and B

 

  1. E)

 

A, B, and C

 

Answer:

 

D

 

Section:

 

 

7.1

 

4)

 

Which of the following statements is incorrect about benzene?

 

  1. A)

 

All of the carbon atoms are sp hybridized.

 

  1. B)

 

It has delocalized electrons.

 

  1. C)

 

The carbon-carbon bond lengths are all the same.

 

  1. D)

 

The carbon-hydrogen bond lengths are all the same.

 

  1. E)

 

All twelve atoms lie in the same plane.

 

Answer:

 

A

 

Section:

 

 

7.2

 

5)

 

Which of the following statements about benzene is correct?

 

  1. A)

 

All of the carbon atoms are sp3 hybridized.

 

  1. B)

 

It has no delocalized electrons.

 

  1. C)

 

The carbon-carbon bond length is longer than that of ethane.

 

  1. D)

 

It is a planar molecule.

 

  1. E)

 

The carbon-hydrogen bonds are not the same length.

 

Answer:

 

D

 

Section:

 

 

7.2

 

6)

 

The declocalized π system in benzene is formed by a cyclic overlap of 6 __________ orbitals.

 

  1. A)

 

s

 

  1. B)

 

p

 

  1. C)

 

sp

 

  1. D)

 

sp2

 

  1. E)

 

sp3

 

Answer:

 

B

 

Section:

 

 

7.2

 

7)

 

Which of the following pairs are resonance structures?

 

 

 

  1. A)

 

I

 

  1. B)

 

II

 

  1. C)

 

III

 

  1. D)

 

IV

 

  1. E)

 

V

 

Answer:

 

C

 

Section:

 

 

7.3

 

8)

 

Which of the following pairs are resonance structures?

 

 

 

  1. A)

 

I

 

  1. B)

 

II

 

  1. C)

 

III

 

  1. D)

 

IV

 

  1. E)

 

V

 

Answer:

 

C

 

Section:

 

 

7.3

 

9)

 

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

 

 

 

 

  1. A)

 

I

 

  1. B)

 

II

 

  1. C)

 

III

 

  1. D)

 

IV

 

Answer:

 

D

 

Section:

 

 

7.3

 

10)

 

Draw two other resonance contributors for the following compound:

 

 

 

Answer:

 

 

 

 

Section:

 

 

7.4

 

11)

 

Are the following pairs of structures resonance contributors or different compounds?

 

 

 

Answer:

 

They are resonance contributors.

 

Section:

 

 

7.4

 

12)

 

Draw the important resonance structures of:

 

H2 — N:

 

 

Answer:

 

 

 

 

Section:

 

 

7.4

 

13)

 

Draw the important resonance structure of:

 

 

 

Answer:

 

 

 

 

Section:

 

 

7.4

 

14)

 

Draw the important resonance structures of:

 

 

 

Answer:

 

 

 

 

Section:

 

 

7.4

 

15)

 

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

 

 

 

Answer:

 

 

 

 

Section:

 

 

7.4

 

16)

 

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

 

 

 

Answer:

 

 

 

 

Section:

 

 

7.4

 

17)

 

Draw all major resonance contributors of the species below.

 

 

 

Answer:

 

 

 

 

Section:

 

 

7.4

 

18)

 

Draw all major resonance contributors of the species below.

 

 

 

Answer:

 

 

 

 

Section:

 

 

7.4 and 7.5

 

19)

 

Draw all major resonance contributors of the species below.

 

 

 

Answer:

 

 

 

 

Section:

 

 

7.4 and 7.5

 

20)

 

Draw all major resonance contributors of the species below.

 

 

 

Answer:

 

 

 

 

Section:

 

 

7.4 and 7.5

 

21)

 

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

 

 

 

  1. A)

 

 

 

 

  1. B)

 

 

 

 

  1. C)

 

 

 

 

  1. D)

 

 

 

 

  1. E)

 

 

 

 

Answer:

 

E

 

Section:

 

 

7.5

 

22)

 

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

 

 

 

 

Answer:

 

C is the most important contributor because all the atoms have complete octets and the negative charges are on the most electronegative atoms.

 

Section:

 

 

7.4 and 7.5

 

23)

 

Order the following molecules in decreasing order of stability:

 

 

 

Answer:

 

a > c > b

aromatic > linear > antiaromatic

 

Section:

 

 

7.5

 

24)

 

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

 

Answer:

 

Stabilization results from delocalization of charge.

 

Section:

 

 

7.5

 

25)

 

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

 

Answer:

 

The acetate ion is a hybrid of the two resonance contributors below. Each oxygen in this ion has the same charge (-1/2); the oxygen atoms are indistinguishable and the carbon-oxygen bonds are identical.

 

 

 

Section:

 

 

7.6

 

26)

 

Which of the following is incorrect?

 

  1. A)

 

Resonance stabilization is the extra stability a compound gains from having delocalized electrons.

 

  1. B)

 

Delocalized electrons destabilize a compound.

 

  1. C)

 

The greater the number of relatively stable resonance contributors, the greater is the resonance stabilization.

 

  1. D)

 

A and C

 

  1. E)

 

B and C

 

Answer:

 

B

 

Section:

 

 

7.6 and 7.7

 

27)

 

Which of the following is an allylic cation?

 

 

 

  1. A)

 

I

 

  1. B)

 

II

 

  1. C)

 

III

 

  1. D)

 

IV

 

  1. E)

 

V

 

Answer:

 

B

 

Section:

 

 

7.7

 

28)

 

Which of the following is a benzylic cation?

 

 

 

  1. A)

 

I

 

  1. B)

 

II

 

  1. C)

 

III

 

  1. D)

 

IV

 

  1. E)

 

V

 

Answer:

 

D

 

Section:

 

 

7.7

 

29)

 

Which of the following is the most stable cation?

 

 

 

  1. A)

 

I

 

  1. B)

 

II

 

  1. C)

 

III

 

  1. D)

 

IV

 

  1. E)

 

V

 

Answer:

 

C

 

Section:

 

 

7.7

 

30)

 

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

 

 

 

  1. A)

 

2

 

  1. B)

 

3

 

  1. C)

 

4

 

  1. D)

 

5

 

  1. E)

 

zero

 

Answer:

 

E

 

Section:

 

 

7.7

 

31)

 

How many benzylic hydrogens are present in the following molecule?

 

 

 

  1. A)

 

2

 

  1. B)

 

3

 

  1. C)

 

4

 

  1. D)

 

5

 

  1. E)

 

zero

 

Answer:

 

E

 

Section:

 

 

7.7

 

32)

 

Which of the following compounds is more stable? Explain.

 

 

 

Answer:

 

(a) and (b) are both benzylic cations. (b) is more stable because it has more alkyl substituents.

 

Section:

 

 

7.7

 

33)

 

Which of the following is the most stable diene?

 

 

 

  1. A)

 

I

 

  1. B)

 

II

 

  1. C)

 

III

 

  1. D)

 

IV

 

  1. E)

 

V

 

Answer:

 

C

 

Section:

 

 

7.7

 

34)

 

Rank the following dienes in order of increasing stability:

trans-1, 3-pentadiene, cis-1,3-pentadiene, 1,4-pentadiene, and1, 2-pentadiene.

 

Answer:

 

1,2-pentadiene < 1,4-pentadiene < cis-1,3-pentadiene < trans-1,3-pentadiene

 

Section:

 

 

7.7

 

35)

 

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

 

  1. A)

 

sp

 

  1. B)

 

sp2

 

  1. C)

 

sp3

 

  1. D)

 

p

 

  1. E)

 

none of the above

 

Answer:

 

A

 

Section:

 

 

7.7

 

36)

 

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

 

  1. A)

 

conjugated diene

 

  1. B)

 

cumulated diene

 

  1. C)

 

isolated diene

 

  1. D)

 

alkynyl diene

 

  1. E)

 

none of the above

 

Answer:

 

A

 

Section:

 

 

7.7

 

37)

 

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

 

  1. A)

 

conjugated diene

 

  1. B)

 

cumulated diene

 

  1. C)

 

isolated diene

 

  1. D)

 

alkynyl diene

 

  1. E)

 

none of the above

 

Answer:

 

C

 

Section:

 

 

7.7

 

38)

 

Which of the following is an isolated diene?

 

 

 

  1. A)

 

I

 

  1. B)

 

II

 

  1. C)

 

III

 

  1. D)

 

IV

 

  1. E)

 

V

 

Answer:

 

D

 

Section:

 

 

7.7

 

39)

 

Which of the following is a conjugated diene?

 

 

 

  1. A)

 

I

 

  1. B)

 

II

 

  1. C)

 

III

 

  1. D)

 

IV

 

  1. E)

 

V

 

Answer:

 

A

 

Section:

 

 

7.7

 

40)

 

Which of the following is/are the main product(s) of the following reaction?

 

CH2CHCHCH2         ?

 

 

  1. A)

 

 

 

 

  1. B)

 

 

 

 

  1. C)

 

 

 

 

  1. D)

 

A and B

 

  1. E)

 

A and C

 

Answer:

 

E

 

Section:

 

 

7.8

 

41)

 

Which of the following is/are the major product(s) of the following reaction?

 

 

 

  1. A)

 

I

 

  1. B)

 

I and II

 

  1. C)

 

I and III

 

  1. D)

 

II

 

  1. E)

 

III

 

Answer:

 

A

 

Section:

 

 

7.8

 

42)

 

Provide the structure of the major organic product(s) in the reaction below.

 

 

 

Answer:

 

 

 

 

Section:

 

 

7.8

 

43)

 

Which of the following is/are the major product(s) of the following reaction?

 

 

 

  1. A)

 

I

 

  1. B)

 

I and III

 

  1. C)

 

II

 

  1. D)

 

II and III

 

  1. E)

 

III

 

Answer:

 

C

 

Section:

 

 

7.8

 

44)

 

What is/are the product(s) from the following reaction?

 

 

 

  1. A)

 

I only

 

  1. B)

 

II only

 

  1. C)

 

I is minor, II is major

 

  1. D)

 

I is major, II is minor

 

  1. E)

 

equal amounts of I and II

 

Answer:

 

D

 

Section:

 

 

7.8

 

45)

 

What is/are the product(s) of the following reaction?

 

 

 

 

  1. A)

 

I only

 

  1. B)

 

II only

 

  1. C)

 

III only

 

  1. D)

 

I and II

 

  1. E)

 

I and III

 

Answer:

 

E

 

Section:

 

 

7.8

 

46)

 

Arrange the following unsaturated hydrocarbons in order of decreasing reactivity toward HBr addition:

 

 

 

Answer:

 

III > II > IV > I

 

Section:

 

 

7.8

 

47)

 

Provide the structure of the major product which results from 1,2-addition of HBr to the diene shown below.

 

 

 

Answer:

 

 

 

 

Section:

 

 

7.8

 

48)

 

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

 

  1. A)

 

1-bromo-1-butene

 

  1. B)

 

2-bromo-2-butene

 

  1. C)

 

4-bromo-1-butene

 

  1. D)

 

3-bromo-1-butene

 

  1. E)

 

1-bromo-2-butene

 

Answer:

 

E

 

Section:

 

 

7.8

 

49)

 

Which of the following is the strongest acid?

 

  1. A)

 

CH3CH2OH

 

  1. B)

 

CH3OCH3

 

  1. C)

 

 

 

 

  1. D)

 

 

 

 

  1. E)

 

 

 

 

Answer:

 

E

 

Section:

 

 

7.9

 

50)

 

Which of the following is the strongest acid?

 

 

 

  1. A)

 

I

 

  1. B)

 

II

 

  1. C)

 

III

 

  1. D)

 

IV

 

  1. E)

 

V

 

Answer:

 

D

 

Section:

 

 

7.9

 

51)

 

Why is phenol a stronger acid than cyclohexanol?

 

 

 

Answer:

 

The anion of phenol is stabilized by resonance, causing the proton to be more easily abstracted than that of cyclohexanol.

 

Section:

 

 

7.9

 

52)

 

Which of the following ions is most acidic?

 

  1. A)

 

C6H5NH3+

 

  1. B)

 

C6H5CH2NH3+

 

  1. C)

 

(CH3)2CHNH3+

 

  1. D)

 

CH3CH2NH3+

 

  1. E)

 

CH3NH3+

 

Answer:

 

A

 

Section:

 

 

7.9

 

53)

 

Which of the following is the weakest base?

 

  1. A)

 

phenolate ion (C6H5O-)

 

  1. B)

 

ethoxide ion (CH3CH2O-)

 

  1. C)

 

hydroxide ion (HO-)

 

  1. D)

 

acetate ion (CH3CO2-)

 

  1. E)

 

methoxide ion (CH3O-)

 

Answer:

 

D

 

Section:

 

 

7.9

 

54)

 

Which of the following is correct concerning Ultraviolet and Visible spectroscopy (UV/Vis)?

 

  1. A)

 

It provides information about compounds containing conjugated double bonds.

 

  1. B)

 

Visible light has wavelengths ranging from 180 nm to 400 nm.

 

  1. C)

 

Ultraviolet light has wavelengths ranging from 400 nm to 780 nm.

 

  1. D)

 

B and C

 

  1. E)

 

A, B, and C

 

Answer:

 

A

 

Section:

 

 

7.10

 

55)

 

How is lmax described?

 

Answer:

 

lmax is the highest point of the absorption band in the UV spectrum.

 

Section:

 

 

7.10

 

56)

 

What is the effect on the wavelength in a UV/Vis spectrum if the number of conjugated double bonds in a compound labeled A is greater than the number of conjugated double bonds in a compound labeled B.

 

Answer:

 

Compound A will have a longer wavelength or the lmax value for compound A is larger than the lmax  value for compound B.

 

Section:

 

 

7.10 and 7.11

 

57)

 

Which of the following compounds exhibits the highest λmax in UV spectra?

 

 

 

  1. A)

 

I

 

  1. B)

 

II

 

  1. C)

 

III

 

  1. D)

 

IV

 

  1. E)

 

V

 

Answer:

 

D

 

Section:

 

 

7.11

 

58)

 

Which of the following compounds absorbs the longest wavelength of UV-visible light?

 

  1. A)

 

(E)-2-butene

 

  1. B)

 

(Z)-2-butene

 

  1. C)

 

1-hexene

 

  1. D)

 

(Z)-1,3-hexadiene

 

  1. E)

 

(E)-1,3,5-hexatriene

 

Answer:

 

E

 

Section:

 

 

7.11

 

59)

 

Which color is observed when a sample absorbs light at 650 nm?

 

  1. A)

 

yellow

 

  1. B)

 

orange

 

  1. C)

 

red

 

  1. D)

 

green

 

  1. E)

 

blue

 

Answer:

 

E

 

Section:

 

 

7.12

 

60)

 

When a solution of an organic compound absorbs light whose wavelength is 400 nm, the solution appears __________.

 

  1. A)

 

yellow

 

  1. B)

 

red

 

  1. C)

 

purple

 

  1. D)

 

blue

 

  1. E)

 

white

 

Answer:

 

A

 

Section:

 

 

7.12

 

61)

 

When a solution of an organic compound absorbs light whose wavelength is 700 nm, the solution appears __________.

 

  1. A)

 

yellow

 

  1. B)

 

green

 

  1. C)

 

red

 

  1. D)

 

orange

 

  1. E)

 

purple

 

Answer:

 

B

 

Section:

 

 

7.12

 

62)

 

Which color is observed when a sample absorbs light at 400 nm?

 

  1. A)

 

blue

 

  1. B)

 

green

 

  1. C)

 

yellow

 

  1. D)

 

red

 

Answer:

 

C

 

Section:

 

 

7.12

 

63)

 

Which color is observed when a sample absorbs light at 500 nm?

 

  1. A)

 

blue

 

  1. B)

 

yellow

 

  1. C)

 

green

 

  1. D)

 

orange

 

Answer:

 

D

 

Section:

 

 

7.12

 

64)

 

White light is a mixture of all wavelengths of visible light.

 

Answer:

 

TRUE

 

Section:

 

 

7.12