Deck 16: Conjugated Pi Systems and Pericyclic Reactions

Question 1

Provide the structure for (1E,3Z)-1-methoxy-2-methyl-1,3-pentadiene.

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

Answer 1

I

Question 2

What is the IUPAC name for the following compound?

A) (2E, 4Z)-2,4-hexadiene
B) (2E, 4Z)-1,4-dimethyl-1,3-butadiene
C) (2Z, 4Z)-1,4-dimethyl-1,3-butadiene
D) (2Z, 4Z)-2,4-hexadiene
E) None of these

Answer 2

(2E, 4Z)-2,4-hexadiene

Question 3

What is the IUPAC name for the following compound?

Answer 3

1-isopropyl-4-methyl-1,3-cyclopentadiene

Question 4

Provide the structure for (Z)-2-methyl-2,4-hexadiene.

Question 5

What is the IUPAC name for the following compound?

A) (2E,4Z,6E)-3,4,7,8-tetramethyl-2,4,6-heptatriene
B) (2Z,4E)-3,4,7-trimethyl-2,4,6-octatriene
C) (2E,4Z,6E)-2,5,6,7-tetramethyl-3,5,7-heptatriene
D) (2E,4Z)- 2,5,6-trimethyl-3,5,7-octatriene
E) (4E,6E)-2,5,6-trimethyl-2,4,6-octatriene

Question 6

Which of the following compounds is an isolated diene?

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

Question 7

Classify the following compounds as having cumulated, conjugated or isolated double bonds?

Question 8

Zingiberene, a terpene found in ginger, has the following structure. Classify the $\pi$ bonds in zingiberene as conjugated, cumulated or isolated.

Question 9

Identify the cumulated diene.

A) 4-methyl-1,3-heptadiene
B) 3-methyl-1,5-heptadiene
C) 2-methyl-2,4-heptadiene
D) 4-methyl-1,4-heptadiene
E) 5-methyl-2,3-heptadiene

Question 10

Dienes with adjacent π bonds are classified as ______.

A) isolated
B) cumulated
C) skipped
D) conjugated
E) none of these

Question 11

Which of the following compounds have isolated double bonds?

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

Question 12

What is the IUPAC name for the following compound?

A) 1-chloro-1-methyl-2,5-cyclohexadiene
B) 3-chloro-3-methyl-1,4-cyclohexadiene
C) 6-chloro-6-methyl-1,4-cyclohexadiene
D) 2-chloro-2-methyl-1,3-cyclohexadiene
E) None of these

Question 13

Vitamin D₃ has the following structure. Classify the $\pi$ bonds in vitamin D₃ as conjugated, cumulated or isolated.

Question 14

Identify the conjugated diene(s).

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

Question 15

Identify the isolated dienes.

A) 4-methyl-1,3-heptadiene
B) 3-methyl-1,5-heptadiene
C) 2-methyl-2,4-heptadiene
D) 4-methyl-1,4-heptadiene
E) 5-methyl-2,3-heptadiene

Question 16

Identify the conjugated diene(s).
A. 4-methyl-1,3-heptadiene
B. 3-methyl-1,5-heptadiene
C. 2-methyl-2,4-heptadiene
D. 4-methyl-1,4-heptadiene
E. 5-methyl-2,3-heptadiene

Question 17

Provide the structure for (E)-1,3-pentadiene.

Question 18

Dienes with alternate π and σ bonds are classified as ______.

A) isolated
B) cumulated
C) skipped
D) conjugated
E) none of these

Question 19

Which of the following compounds have conjugated double bonds?

A) II and V
B) II, IV, and V
C) I and III
D) I, III, and IV
E) all of them

Question 20

Dienes with $\pi$ bonds separated by two or more σ bonds are classified as ______.

A) isolated
B) cumulated
C) skipped
D) conjugated
E) none of these

Question 21

Rank the following dienes in order of decreasing heat of hydrogenation (highest to lowest).

Question 22

Predict the product(s) for the following reaction.

A) I
B) II
C) III
D) IV
E) both I & III

Question 23

Which of the following indicated C-C bonds is(are) the shortest?

A) I
B) II
C) III
D) both I and II

Question 24

Which one of the following dienes is most stable?

A) CH₃CH=CHCH=CHCH₃
B) CH₃CH=CHCH₂CH=CH₂
C) CH₂=CHCH₂CH₂CH=CH₂
D) CH₂=CHCH(CH₃)CH=CH₂
E) CH₃CH=C=CHCH₂CH₃

Question 25

Predict the product for the following reaction.

Question 26

Provide the reagents necessary to carry out the following conversion.

Question 27

Rank the following dienes in order of decreasing heat of hydrogenation (highest to lowest).

Question 28

Both s-cis and s-trans conformers of 1,3-butadiene have a continuous conjugated $\pi$ system. Which of the following statements is true about the s-cis conformer?

A) The s-cis conformer is lower in energy than the s-trans conformer
B) The s-cis conformer is higher in energy than the s-trans conformer
C) The s-cis conformer has equal energy as the s-trans conformer
D) none of these

Question 29

Rank the following dienes in order of increasing stability (least to most).

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

Question 30

Provide the reagents necessary to carry out the following conversion.

Question 31

Predict the product(s) for the following reaction.

A) I
B) II
C) III
D) IV
E) both I & III

Question 32

Which one of the following dienes is least stable?

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

Question 33

Predict the product for the following reaction.

Question 34

Which one of the following dienes is least stable?

A) CH₃CH=CHCH=CHCH₃
B) CH₃CH=CHCH₂CH=CH₂
C) CH₂=CHCH₂CH₂CH=CH₂
D) CH₂=CHCH(CH₃)CH=CH₂
E) CH₃CH=C=CHCH₂CH₃

Question 35

Provide the structure for (S,E)-3-t-butyl-4-methyl-1,4-hexadiene.

Question 36

Which one of the following dienes will have the highest heat of hydrogenation?

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

Question 37

Which one of the following dienes will have the lowest heat of hydrogenation?

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

Question 38

Which one of the following dienes is most stable?

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

Question 39

Provide the reagents necessary to carry out the following conversion.

Question 40

Which of the following indicated C-C bonds is (are) the longest?

A) I
B) II
C) III
D) both I and II

Question 41

The reaction of 1,3-butadiene with hydrogen halide at 0°C will undergo _____ -addition under ____________ control.

Question 42

The reaction of 1,3-butadiene with hydrogen halide at 40°C will undergo _____ -addition under ____________ control.

Question 43

Which one of the following represents the lowest energy $\pi$ -bonding molecular orbital of 1,3-butadiene?

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

Question 44

Identify the product of a thermodynamically-controlled reaction.

A) the most stable product
B) the product whose formation requires the smallest free energy of activation
C) the product that can be formed in the fewest steps
D) the product that is formed at the fastest rate
E) none of these

Question 45

Predict the major product for the following reaction.

Question 46

Provide the structure of the 1,4 addition product for the reaction of 1,3-hexadiene with Br₂/CCl₄.

Question 47

Provide the structure of the 1,2 addition product for the following reaction.

Question 48

Predict the possible major products for the following reaction.

Question 49

How many $\pi$ -bonding molecular orbitals does 1,3-pentadiene have?

A) 1
B) 2
C) 3
D) 4
E) none

Question 50

Which major product(s) is(are) formed in the following reaction?

A) I and V
B) II and IV
C) III and IV
D) I, III and VI
E) II, IV and V

Question 51

Identify the products of a reaction under kinetic control.

A) the most stable product
B) the product whose formation requires the smallest free energy of activation
C) the product that can be formed in the fewest steps
D) the product that is formed at the fastest rate
E) none of these

Question 52

Which one of the following represents the highest energy $\pi$ -antibonding molecular orbital of 1,3-butadiene?

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

Question 53

Which one of the following represents the LUMO of 1,3,5-hexatriene?

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

Question 54

How many electrons does the LUMO of 2,4-hexadiene have in its ground state?

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

Question 55

Which one of the following represents the HOMO of 1,3,5-hexatriene?

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

Question 56

How many electrons does the HOMO of 2,4-hexadiene have in its ground state?

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

Question 57

How many electrons does the HOMO of 1,3-pentadiene have in its excited state?

A) 1
B) 2
C) 3
D) 4
E) none

Question 58

Which one of the following compounds is not a product of the reaction between 1,3-butadiene and HBr?

A) (S)-3-bromo-1-butene
B) (R)-3-bromo-1-butene
C) (E)-1-bromo-2-butene
D) (Z)-1-bromo-2-butene
E) (Z)-2-bromo-2-butene

Question 59

Predict the possible products for the following reaction and provide a curved arrow mechanism for the formation of these products.

Question 60

Predict the product(s) for the following reaction.

Question 61

Predict the major product for the following reaction.

Question 62

Which of the following diene(s) cannot undergo the Diels-Alder reaction?

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

Question 63

Identify the pericyclic reaction in which two sigma bonds are broken and two pi bonds are formed.

A) sigmatropic rearrangement
B) cycloaddition reaction
C) electrolytic reaction
D) this is not a pericyclic reaction

Question 64

Identify the pericyclic reaction in which one sigma bond is formed and one pi bond is broken.

A) sigmatropic rearrangement
B) cycloaddition reaction
C) electrolytic reaction
D) this is not a pericyclic reaction

Question 65

Which one of the following dienophiles is least reactive in the Diels-Alder reaction?

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

Question 66

The polymerization of isoprene to produce synthetic rubber is a special case of ____- addition.

Question 67

Identify the pericyclic reaction in which no sigma bonds are formed and no pi bonds are broken.

A) sigmatropic rearrangement
B) cycloaddition reaction
C) electrolytic reaction
D) this is not a pericyclic reaction

Question 68

Which of the following diene(s) can undergo the Diels-Alder reaction?

A) I
B) II
C) III
D) IV
E) All of the these

Question 69

What is the correct classification of the following pericyclic reaction?

A) electrophilic addition
B) sigmatropic rearrangement
C) cycloaddition
D) electrocyclic reaction
E) C & D

Question 70

Predict the major product for the following reaction and explain why it is major product.

Question 71

Predict the major product for the following reaction.

Question 72

Which statement is NOT true about the Diels-Alder reaction?

A) It is a [4+2] cycloaddition reaction.
B) The diene must be in the s-cis conformation to react.
C) Most Diels-Alder reactions are reversible.
D) It is a sigmatropic rearrangement.
E) Electron donating groups on the diene and electron withdrawing groups on the dienophile favor product formation.

Question 73

Identify the pericyclic reaction in which two sigma bonds are formed and two pi bonds are broken.

A) sigmatropic rearrangement
B) cycloaddition reaction
C) electrolytic reaction
D) this is not a pericyclic reaction

Question 74

Provide the structure for 1,2 addition product for the following reaction and explain why it is a major product rather than 1,4 addition product.

Question 75

Which one of the following dienophiles is most reactive in the Diels-Alder reaction?

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

Question 76

The addition of a _____________ bond improves the elasticity in synthetic rubber.

Question 77

What is the correct classification of the following pericyclic reaction?

A) electrophilic addition
B) sigmatropic rearrangement
C) cycloaddition
D) electrocyclic reaction
E) C and D

Question 78

The Diels Alder reaction is a concerted reaction. Define concerted.

A) The product contains a cyclic ring.
B) The diene must be in the s-cis conformation to react.
C) All changes in bonding (bond making and bond breaking) occur simultaneously.
D) It is an endothermic reaction.
E) Both exo and endo products are formed.

Question 79

What is the correct classification of the following pericyclic reaction?

A) electrophilic addition
B) sigmatropic rearrangement
C) cycloaddition
D) electrocyclic reaction
E) C & D

Question 80

Which of the following is true of pericyclic reactions?

A) they are concerted reactions
B) proceed via a cyclic transition state
C) no intermediates are formed
D) all of these