Deck 3: Molecules in Motion: Conformations by Rotation

Question 1

Which of the following conformations exhibits the highest torsional strain?

A)
B)
C)
D)

Answer 1

Question 2

Which of the following Newman projections is in a gauche conformation?

A)
B)
C)
D)

Answer 2

Question 3

Which of the following represents the order of conformations in a cyclohexane ring flip?

A)chair $\rightarrow$ half chair $\rightarrow$ twist boat $\rightarrow$ boat $\rightarrow$ twist boat $\rightarrow$ half chair $\rightarrow$ chair
B)chair $\rightarrow$ half chair $\rightarrow$ boat $\rightarrow$ twist boat $\rightarrow$ boat $\rightarrow$ half chair $\rightarrow$ chair
C)chair $\rightarrow$ twist boat $\rightarrow$ half chair $\rightarrow$ boat $\rightarrow$ half chair $\rightarrow$ twist boat $\rightarrow$ chair
D)chair $\rightarrow$ twist boat $\rightarrow$ boat $\rightarrow$ half chair $\rightarrow$ boat $\rightarrow$ twist boat $\rightarrow$ chair

Answer 3

chair $\rightarrow$ half chair $\rightarrow$ twist boat $\rightarrow$ boat $\rightarrow$ twist boat $\rightarrow$ half chair $\rightarrow$ chair

Question 4

Which of the following conformations of cyclohexane is highest in energy?

A)chair
B)half-chair
C)boat
D)twist-boat

Question 5

Which of the following molecules has two equally stable chair conformations?

A)
B)
C)
D)

Question 6

Which of the following conformations exhibits the largest steric strain?

A)
B)
C)
D)

Question 7

Which of the following best describes cyclohexane in the chair conformation?

A)It contains torsional strain.
B)It contains angle strain.
C)It contains both torsional and angle strain.
D)It contains neither torsional nor angle strain.

Question 8

Which of the following best describes the bromo group in the molecule shown below?

A)It is equatorial and above the plane of the ring.
B)It is equatorial and below the plane of the ring.
C)It is axial and above the plane of the ring.
D)It is axial and below the plane of the ring.

Question 9

Which of the following molecules exhibits the least ring strain?

A)cyclobutane
B)cyclopentane
C)cyclohexane
D)cycloheptane

Question 10

What is the relationship between the bromo and chloro substituents in the molecule shown below?

A)cis
B)trans
C)syn
D)anti

Question 11

Which of the following is a chair conformation of the structure shown below?

A)
B)
C)
D)

Question 12

Which of the following molecules has two equally stable chair conformations?

A)trans-1,4-dimethylcyclohexane
B)cis-1,4-dimethylcyclohexane
C)trans-1-ethyl-4-methylcyclohexane
D)cis-1-ethyl-4-methylcyclohexane

Question 13

Which of the following best describes a cyclopropane ring?

A)It contains torsional strain.
B)It contains angle strain.
C)It contains both torsional and angle strain.
D)It contains neither torsional nor angle strain.

Question 14

Which of the following best describes the molecule shown below?

A)Both bromo and chloro are axial.
B)Both bromo and chloro are equatorial.
C)Bromo is axial and chloro is equatorial.
D)Bromo is equatorial and chloro is axial.

Question 15

Which of the following represents a Newman projection of the molecule shown below?

A)
B)
C)
D)

Question 16

Which of the following represents the Newman projection shown below?

A)
B)
C)
D)

Question 17

Which of the following exhibits the largest angle strain?

A)cyclobutane
B)cyclopentane
C)cyclohexane
D)cycloheptane

Question 18

What is the optimal dihedral angle between substituents of a Newman projection in a staggered conformation?

A)15°
B)30°
C)60°
D)90°

Question 19

Which of the following represents the most stable chair conformation of the molecule shown below?

A)
B)
C)
D)

Question 20

Which of the following represents the most stable conformation of cis-1-bromo-2-chlorocyclohexane?

A)
B)
C)
D)

Question 21

Which of the following is a Newman conformation of the structure shown below?

A)
B)
C)
D)

Question 22

How many possible butterfly conformations exist for cyclobutane?

A)1
B)2
C)4
D)8

Question 23

Which of the following best describes the Newman conformation shown below?

A)gauche
B)eclipsed
C)antiperiplanar
D)torsional

Question 24

What is the torsional angle between the alcohol and methyl substituents shown below?

A)30°
B)60°
C)90°
D)120°

Question 25

Which of the following is a Newman projection of the molecule shown below?

A)
B)
C)
D)

Question 26

Which of the following does NOT represents a ring flip of the chair structure shown below?

A)
B)
C)
D)

Question 27

Which of the following best describes the conformation of a cyclobutane ring?

A)envelope
B)chair
C)boat
D)butterfly

Question 28

Which of the following is a Newman projection of the molecule shown below?

A)
B)
C)
D)

Question 29

How many possible envelope conformations exist for cyclopentane?

A)1
B)2
C)5
D)10

Question 30

Which of the following best describes the conformation of a cyclopentane ring?

A)envelope
B)chair
C)boat
D)butterfly

Question 31

Which group would you expect to have the largest A-value?

A)methyl
B)ethyl
C)isopropyl
D)tert-butyl

Question 32

Which of the following represents a conformation of the molecule shown below?

A)
B)
C)
D)

Question 33

Which of the following best describes the relationship between bromo and chloro in the molecule shown below?

A)cis
B)trans
C)syn
D)anti

Question 34

Which of the following represents a ring flip of the chair structure shown below?

A)
B)
C)
D)

Question 35

Which of the following has the most conformational stability?

A)
B)
C)
D)

Question 36

Which of the following best describes the molecule shown below?

A)Both bromo and chloro are axial.
B)Both bromo and chloro are equatorial.
C)Bromo is axial and chloro is equatorial.
D)Bromo is equatorial and chloro is axial.

Question 37

What best describes the relationship between bromo and chloro in the molecule shown below?

A)cis
B)trans
C)syn
D)anti

Question 38

Which of the following molecules contains the most rotatable bonds?

A)
B)
C)
D)

Question 39

What is the torsional angle between the chloro and propyl substituents shown below?

A)15°
B)30°
C)45°
D)60°

Question 40

What is the interior angle of a cyclobutane ring in its most stable conformation?

A)less than 90°
B)90°
C)greater than 90°
D)impossible to determine

Question 41

A cyclohexane twist-boat conformation is more strained then the half-chair conformation.

Question 42

A Newman projection with eclipsed substituents is considered gauche.

Question 43

The chair conformations of trans-1,4-dimethylcyclohexane are equal in energy.

Question 44

Free rotation is allowed around single bonds.

Question 45

Cyclobutane rings adopt an envelope conformation.

Question 46

The chair conformation is the most stable conformation of cyclohexane rings.

Question 47

An eclipsed confirmation has only steric strain.

Question 48

Large substituents prefer to point equatorial in cyclohexane chair conformations.

Question 49

The most stable conformation of cyclopropane is planar.

Question 50

The chair conformations of trans-1,3-dimethylcyclohexane are equal in energy.

Question 51

Axial substituents exist above and below the plane of the ring.

Question 52

The interpenetration of electron clouds from nearby substituents is a result of torsional strain.

Question 53

A cyclohexane twist-boat conformation is more strained than the boat conformation.

Question 54

A cyclohexane boat conformation is more strained than the half chair conformation.

Question 55

Which cyclopropane ring would be more strained and why?

A)A because of increased angle strain
B)A because of increased torsional strain
C)B because of increased angle strain
D)B because of increased torsional strain

Question 56

Cyclopentane rings have 10 possible envelope conformations available to them.

Question 57

Cyclopentane rings adopt a boat conformation.

Question 58

The most stable conformation of cyclobutane is planar.

Question 59

Ring-flips of cyclohexane ring chair conformations result in an inversion of stereochemistry.

Question 60

The chair conformations of cis-1,3-dimethylcyclohexane are equal in energy.

Question 61

Cyclobutane adopts a_______________ conformation.

Question 62

Cyclohexane can undergo chair flips rapidly at room temperature.

Question 63

The difference in energy between two chair conformations is referred to as an _______________.

Question 64

A gauche confirmation leads to _______________ strain.

Question 65

Cyclopropane has a lower heat of combustion then propane.

Question 66

Draw the Newman projection of the following molecule looking through the bond indicated by a *.

Question 67

The interpenetration of electron clouds from nearby substituents is a result of_______________ strain.

Question 68

The _______________ is the highest energy cyclohexane conformation.

Question 69

Cyclopentane rings adopt a _______________ conformation.

Question 70

Chair conformations still experience angle strain.

Question 71

The boat conformation is the least stable cyclohexane conformation.

Question 72

A Newman projection whereupon the dihedral angle between two substituents is 180° is said to be in a _______________ conformation.

Question 73

Draw both chair conformations of the molecule shown below and indicate which is more stable.

Question 74

Draw the Newman projection of the following molecule looking through the bond indicated by a *.

Question 75

A Newman projection whereupon the dihedral angle between two substituents is 0° is said to be in a _______________ conformation.

Question 76

Draw the ring flip of the following molecule,shown below.

Question 77

Molecules that exist in different conformations are called _______________ .

Question 78

Axial substituents in a chair conformation experience steric strain through 1,2-diaxial interactions

Question 79

A-values represent the torsional strain in chair conformations.

Question 80

A Newman projection whereupon the dihedral angle between two substituents is 180° is said to be in a _______________ conformation.