Question 1

Which of the following is a type of pericyclic reaction?

Accepted Answer

A)  electrocyclic reactions
B)  acyclic reactions
C)  cycloelimination reactions
D)  electrophilic reactionsE) None of the above
F) A) and B)

Question 2

Which of the following statements about cycloaddition reactions is true?

Accepted Answer

A)  Cycloaddition reactions can be initiated by heat only.
B)  Cycloaddition reactions can be initiated by light only.
C)  Cycloaddition reactions can be initiated by heat or light.
D)  Cycloaddition reactions are identified by the number of p electrons in the two products.E) None of the above
F) All of the above

Question 3

Which of the following statements about molecular orbitals is true?

Accepted Answer

A)  The number of molecular orbitals formed is different from the number of atomic orbitals used.
B)  The number of molecular orbitals formed is equal to the number of atomic orbitals used.
C)  The number of molecular orbitals formed is equal to twice the number of atomic orbitals used.
D)  The number of molecular orbitals formed is equal to half the number of atomic orbitals used.E) A) and B)
F) A) and C)

Question 4

Which of the following is not a correct designation for a sigmatropic rearrangement?

Accepted Answer

A)  [1,3]
B)  [1,5]
C)  [3,3]
D)  [3,1]E) All of the above
F) C) and D)

Question 5

Which of the following statements about photochemical electrocyclic reactions is not true?

Accepted Answer

A)  In photochemical reactions, we consider the orbitals of the HOMO of the excited state to determine the course of the reaction.
B)  Photochemical electrocyclic reactions occur in a conrotatory fashion for a conjugated polyene with an odd number of pbonds.
C)  Photochemical electrocyclic reactions occur in a disrotatory fashion for a conjugated polyene with an even number of pbonds.
D)  In photochemical reactions, we consider the orbitals of the LUMO of the excited state to determine the course of the reaction.E) B) and C)
F) All of the above

Question 6

How many p molecular orbitals are present in 1,3,5,7,9-decapentaene?

Accepted Answer

A)  4
B)  5
C)  10
D)  12E) A) and C)
F) A) and B)

Question 7

Which of the following statements about pericyclic reactions is true?

Accepted Answer

A)  Pericyclic reactions occur by way of ionic intermediates.
B)  Pericyclic reactions occur by way of radical intermediates.
C)  Pericyclic reactions involve multiple steps.
D)  Reactive intermediates are not formed in pericyclic reactions.E) None of the above
F) All of the above

Question 8

What type of cycloaddition reaction is shown in the following equation?

Accepted Answer

A)  [2+2]
B)  [4+2]
C)  [4+4]
D)  [0+2]E) A) and B)
F) B) and C)

Question 9

Which of the following statements about sigmatropic rearrangements and orbital symmetry is not true?

Accepted Answer

A)  Reactions involving six atoms or fewer must take place by suprafacial pathways.
B)  In a suprafacial rearrangement, the new sbond forms on the opposite side of the psystem as the broken s bond.
C)  In an antarafacial rearrangement, the new sbond forms on the opposite side of the psystem as the broken s bond.
D)  In a suprafacial rearrangement, the new sbond forms on the same side of the p system as the broken s bond.E) A) and B)
F) B) and C)

Question 10

Consider the following reaction sequence.What is the correct classification of the second reaction in the sequence?
 Consider the following reaction sequence.What is the correct classification of the second reaction in the sequence?   A) [2 + 2] Cycloaddition B) [6 + 4] Cycloaddition C) [4 + 4] Cycloaddition D) [4 + 2] Cycloaddition" class="answers-bank-image d-inline" rel="preload" >

Accepted Answer

A)  [2 + 2] Cycloaddition
B)  [6 + 4] Cycloaddition
C)  [4 + 4] Cycloaddition
D)  [4 + 2] CycloadditionE) A) and D)
F) All of the above

Question 11

Which of the following statements about electrocyclic ring closure is not true?

Accepted Answer

A)  It is an intramolecular reaction.
B)  It requires heat or light.
C)  The cyclic product contains one more s bond and one fewer p bond than the reactants.
D)  The cyclic product contains one more p bond and one fewer s bond than the reactants.E) A) and B)
F) All of the above

Question 12

How many bonding molecular orbitals are present in 1,3,5-hexatriene?

Accepted Answer

A)  3
B)  4
C)  5
D)  6E) All of the above
F) A) and C)

Question 13

How many bonding molecular orbitals are present in 1,3,5,7,9-decapentaene?

Accepted Answer

A)  4
B)  5
C)  10
D)  12E) A) and D)
F) C) and D)

Question 14

Predict the major organic product(s)  of the following electrocyclic reaction.

Accepted Answer

A)  Only I
B)  Only II
C)  Only III
D)  Only I and IIE) C) and D)
F) A) and B)

Question 15

Which of the following statements about cycloaddition reactions is not true?

Accepted Answer

A)  Cycloaddition reactions form a cyclic product with two new s bonds.
B)  The course of the reaction is determined by the symmetry of the molecular orbitals of the products.
C)  Cycloaddition reactions are concerted.
D)  Cycloaddition reactions are stereospecific.E) None of the above
F) A) and B)

Question 16

Which of the following statements about pericyclic reactions is not true?

Accepted Answer

A)  Pericyclic reactions are concerted reactions.
B)  Pericyclic reactions proceed through a cyclic transition state.
C)  Pericyclic reactions are not stereospecific.
D)  Pericyclic reactions require light or heat.E) A) and D)
F) All of the above

Question 17

What type of sigmatropic rearrangement is illustrated below?

Accepted Answer

A)  [1,3]
B)  [1,4]
C)  [3,3]
D)  [1,5]E) B) and C)
F) A) and D)

Question 18

What is the major organic product of the following Claisen rearrangement?

Accepted Answer

A)  I
B)  II
C)  III
D)  IVE) A) and B)
F) All of the above

Question 19

Predict the major organic product(s)  of the following electrocyclic reaction.

Accepted Answer

A)  Only I
B)  Only II
C)  Only III
D)  Only I and IIE) C) and D)
F) B) and C)

Question 20

Which of the following statements about electrocyclic reactions is true?

Accepted Answer

A)  An electrocyclic reaction is generally irreversible.
B)  Generally, an acyclic triene is favored over a six-membered ring at equilibrium.
C)  Generally, a four-membered ring is favored over an acyclic diene at equilibrium.
D)  An electrocyclic reaction is generally reversible.E) A) and D)
F) B) and C)

Exam 27: Pericyclic Reactions

Consider the following reaction sequence.What is the correct classification of the second reaction in the sequence?

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How many bonding molecular orbitals are present in 1,3,5-hexatriene?

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Predict the major organic product(s) of the following electrocyclic reaction.

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How many bonding molecular orbitals are present in 1,3,5,7,9-decapentaene?

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Which of the following is not a correct designation for a sigmatropic rearrangement?

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Which of the following statements about cycloaddition reactions is true?

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Which of the following statements about pericyclic reactions is not true?

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Predict the major organic product(s) of the following electrocyclic reaction.

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Which of the following statements about electrocyclic reactions is true?

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Which of the following statements about molecular orbitals is true?

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Which of the following statements about photochemical electrocyclic reactions is not true?

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Which of the following statements about cycloaddition reactions is not true?

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Which of the following is a type of pericyclic reaction?

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What type of cycloaddition reaction is shown in the following equation?

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What is the major organic product of the following Claisen rearrangement?

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Which of the following statements about pericyclic reactions is true?

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Which of the following statements about sigmatropic rearrangements and orbital symmetry is not true?

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How many p molecular orbitals are present in 1,3,5,7,9-decapentaene?

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What type of sigmatropic rearrangement is illustrated below?

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Which of the following statements about electrocyclic ring closure is not true?

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