Deck 6: Isomerism 1: Conformational and Constitutional Isomers

Question 1

Rank the steric strain of the following types of conformations from highest energy to lowest energy.

A)Anti > eclipsed > gauche
B)Eclipsed > anti > gauche
C)Gauche > anti > eclipsed
D)Eclipsed > gauche > anti

Answer 1

Eclipsed > gauche > anti

Question 2

Which of the following compounds has/have substituents cis to each other?

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

Answer 2

II and IV

Question 3

How many fluorine atoms are in equatorial positions in the following chair structure?

A)One
B)Two
C)Three
D)Four
E)Five

Answer 3

Three

Question 4

Which of the following dash-wedge structures best represents the Newman projection below?

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

Question 5

Which is the least stable cyclohexane conformation?

A)Chair
B)Half-chair
C)Twist-boat
D)Boat
E)Crown

Question 6

Which of the following dash-wedge structures best represents the Newman projection below?

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

Question 7

Which of the following molecules has the largest molar heat of combustion?

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

Question 8

Which substituents are gauche to each other?

A)I and Br
B)I and OH
C)CH₃ and Br
D)H and I
E)Cl and Br

Question 9

The Newman projection looking down the indicated bond in the species below is best represented by which of the following (I,II,III,IV,or V)?

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

Question 10

The Newman projection looking down the indicated bond in the species below is best represented by which of the following (I,II,III,IV,or V)?

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

Question 11

Which conformer is highest in energy?

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

Question 12

Which Newman projection results from rotating the front carbon 240° clockwise?

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

Question 13

Which of the following pairs do not have the same connectivity?

A)Two stereoisomers
B)Two conformational isomers
C)Cyclohexane chair conformations before and after a chair flip
D)Two constitutional isomers
E)Two Newman projection rotamers

Question 14

Which of the following has the least ring strain?

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

Question 15

Which substituents are anti to each other?

A)OCH₃ and H
B)Cl and CH₂CH₃
C)Br and SH
D)H and Cl
E)CH₂CH₃ and Br

Question 16

Which of the following types of isomer differs only by the rotation about single bonds?

A)Constitutional
B)Configurational
C)Conformational
D)Diastereomers
E)Enantiomers

Question 17

Which of the following Newman projections is least stable?

A)I
B)II
C)III
D)IV
E)All are equally stable.

Question 18

How many degrees does the front carbon have to be rotated clockwise to result in a gauche conformer?

A)60°
B)90°
C)109.5°
D)120°
E)300°

Question 19

Which structure best represents the following disubstituted cyclohexane?

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

Question 20

Which molecule represents the chair-flipped conformer of the given compound?

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

Question 21

Calculate the index of hydrogen deficiency for the following formula: C₈H₁₂NOF₂^-.

A)0
B)1
C)2
D)3
E)4

Question 22

Which set of molecules does not consist of constitutional isomers?

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

Question 23

Which of the following isomers is most stable?

A)I
B)II
C)III
D)IV
E)I, II, and III have the same stability and are more stable than IV.

Question 24

Which is the most stable conformation of the given trisubstituted cyclohexane below?

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

Question 25

Which set of molecules are not considered constitutional isomers?

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

Question 26

Perform a conformational analysis of 1,1-dichloropropane looking down the C1-C2 bond.

Question 27

Draw a constitutional isomer for the following compound.

Question 28

Draw the least stable Newman projection for 1-iodobutane looking down the C1-C2 bond.

Question 29

Conformational isomers differ by __________.

Question 30

Which is the most stable chair conformation of the following Haworth projection?

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

Question 31

Perform a conformational analysis of bromoethane looking down the C1-C2 bond.

Question 32

Draw the dash-wedge structure that corresponds to the following Newman projection.

Question 33

Draw the dash-wedge structure that corresponds to the following Newman projection.

Question 34

Which Haworth projection corresponds to the following chair conformation?

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

Question 35

Which of the following chair conformations is lowest in energy?

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

Question 36

Which of the following molecules has the highest IHD?

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

Question 37

Draw the Newman projection that corresponds to the following species.

Question 38

Draw the Newman projection for the following species.

Question 39

What is the most stable chair conformation for the following molecule?

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

Question 40

Draw the most stable Newman projection for 1-bromo-2-chloroethane.

Question 41

Calculate the IHD for the formula C₇H₁₁BrO.

Question 42

Draw the following molecule after it undergoes a chair flip.

Question 43

Draw six constitutional isomers for C₄H₁₁N.

Question 44

Draw the most stable chair conformation for the following molecule.

Question 45

Draw a Haworth projection for the following trisubstituted cyclohexane

Question 46

Clearly draw the following molecule with all of its substituents in axial positions.

Question 47

Explain why cyclohexane has less ring strain than cyclopropane.

Question 48

Draw the most Newman projection for 1-iodobutane looking down the C1-C2 bond.

Question 49

How many of the following chair conformations have CH₃ groups that are trans to each other?

Question 50

Draw a chair structure for the following Haworth structure.

Question 51

Would the cis or trans isomer be more stable for the following disubstituted cyclohexane? Explain.

Question 52

Clearly draw the most stable conformer of the following molecule in chair formation.

Question 53

A molecule has two rings,three double bonds,and two triple bonds.How many IHD units does this molecule have?

Question 54

What is the IHD for the formula C₈H₁₇NOClF?

Question 55

How many CH₃ -CH₃ gauche interactions are present in the following Newman projection?

Question 56

Label each of the following molecules as cis or trans.

Question 57

Draw all alkyne-containing isomers of C₅H₈.

Question 58

Give five constitutional isomers for the formula C₄H₆.

Question 59

Would the cis or trans isomer be more stable for the following disubstituted cyclohexane? Explain.

Question 60

Draw the most stable chair conformation for the following compound.