Question 1

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

Accepted Answer

A)  [2 + 2] Cycloaddition
B)  [6 + 4] Cycloaddition
C)  [4 + 4] Cycloaddition
D)  [4 + 2] CycloadditionE) A) and C)
F) B) and C)

Question 2

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) All of the above
F) A) and D)

Question 3

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

Question 4

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

Accepted Answer

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

Question 5

Which of the following is not a type of pericyclic reactions?

Accepted Answer

A)  cycloadditions
B)  nucleophilic reactions
C)  electrocyclic reactions
D)  sigmatropic rearrangementsE) A) and B)
F) None of the above

Question 6

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) B) and C)
F) A) and D)

Question 7

What is the organic product of the following electrocyclic reaction?

Accepted Answer

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

Question 8

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

Accepted Answer

A)  4
B)  5
C)  10
D)  12E) B) and C)
F) None of the above

Question 9

What type of sigmatropic rearrangement is illustrated below?

Accepted Answer

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

Question 10

Which of the following statements about orbital symmetry and cycloaddition reactions is true?

Accepted Answer

A)  Thermal cycloadditions involving an even number of p bonds proceed by a suprafacial pathway.
B)  Thermal cycloadditions involving an odd number of p bonds proceed by an antarafacial pathway.
C)  Photochemical cycloadditions involving an even number of p bonds proceed by an antarafacial pathway.
D)  Photochemical cycloadditions involving an even number of p bonds proceed by a suprafacial pathway.E) A) and B)
F) A) and C) D

Question 11

Which of the following statements about the Claisen rearrangement is true?

Accepted Answer

A)  The Claisen rearrangement occurs readily in a suprafacial pathway under photochemical conditions.
B)  The Claisen rearrangement occurs readily in an antarafacial pathway under thermal conditions.
C)  The Claisen rearrangement involves three electron pairs; two in p bonds and one in a s bond.
D)  The Claisen rearrangement involves the rearrangement of an unsaturated ether to a b,g-unsaturated carbonyl compound.E) None of the above
F) A) and C)

Question 12

What are the two modes of bond formation in cycloaddition reactions?

Accepted Answer

A)  Suprafacial and antarafacial bond formations
B)  Superfacial and antifacial bond formations
C)  Suprafacial and synfacial bond formations
D)  Synfacial and antifacial bond formationsE) B) and D)
F) C) and D)

Question 13

Which of the following statements about pericyclic reactions is true?

Accepted Answer

A)  In pericyclic reactions,bonds are broken and formed in multiple steps.
B)  In pericyclic reactions,all bonds are broken and formed in a single step.
C)  One intermediate has been identified in pericyclic reactions.
D)  The transition state in a pericyclic reaction is acyclic.E) A) and D)
F) None of the above B

Question 14

How many pi electrons are in the ground state LUMO for buta-1,3-diene?

Accepted Answer

A)  0
B)  2
C)  4
D)  6E) A) and B)
F) A) and C)

Question 15

How many pi electrons are in the excited state LUMO for buta-1,3-diene?

Accepted Answer

A)  0
B)  1
C)  2
D)  3E) All of the above
F) B) and D) A

Question 16

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) B) and C)
F) A) and D)

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) A) and D)
F) B) and C)

Question 18

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) A) and D)
F) C) and D)

Question 19

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) A) and B)
F) C) and D)

Question 20

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

Accepted Answer

A)  The number of s bonds in the conjugated polyene determines whether rotation is conrotatory or disrotatory.
B)  Thermal electrocyclic reactions occur in a disrotatory fashion for a conjugated polyene with an odd number of p bonds.
C)  Thermal electrocyclic reactions occur in a conrotatory fashion for a conjugated polyene with an even number of p bonds.
D)  In thermal reactions,we consider the orbitals of the HOMO of the ground state electronic configuration to determine the course of the reaction.E) None of the above
F) All of the above

Exam 25: Pericyclic Reactions

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

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Which of the following statements about pericyclic reactions is true?

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

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

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Which of the following is not a type of pericyclic reactions?

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

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What is the organic product of the following electrocyclic reaction?

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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 orbital symmetry and cycloaddition reactions is true?

Correct AnswerverifiedD

Which of the following statements about the Claisen rearrangement is true?

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What are the two modes of bond formation in cycloaddition reactions?

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Which of the following statements about pericyclic reactions is true?

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How many pi electrons are in the ground state LUMO for buta-1,3-diene?

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How many pi electrons are in the excited state LUMO for buta-1,3-diene?

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

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What type of sigmatropic rearrangement is illustrated below?

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

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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 thermal electrocyclic reactions is not true?

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D

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A

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