Question 1

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) B) and C)
F) None of the above

Question 2

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 D)
F) None of the above

Question 3

What type of cycloaddition reaction is shown below?

Accepted Answer

A)  [2+2]
B)  [4+2]
C)  [4+4]
D)  [0+2]E) All of the above
F) C) and D)

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 B)
F) B) and C)

Question 5

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

Accepted Answer

A)  [1,3] Sigmatropic rearrangement
B)  [1,5] Sigmatropic rearrangement
C)  [3,3] Sigmatropic rearrangement
D)  [5,5] Sigmatropic rearrangementE) B) and C)
F) A) and B)

Question 6

How many pi electrons are in the excited state LUMO for hexa-1,3,5-triene?

Accepted Answer

A)  0
B)  1
C)  2
D)  3E) None of the above
F) C) and D)

Question 7

Which of the following statements about a thermal reaction involving an even number of electron pairs is true?

Accepted Answer

A)  A thermal reaction involving an even number of electron pairs is conrotatory or antarafacial.
B)  A thermal reaction involving an even number of electron pairs is disrotatory or suprafacial.
C)  A thermal reaction involving an even number of electron pairs is conrotatory or suprafacial.
D)  A thermal reaction involving an even number of electron pairs is disrotatory or antarafacial.E) None of the above
F) B) and D)

Question 8

How many pi electrons are in the excited state HOMO for hexa-1,3,5-triene?

Accepted Answer

A)  0
B)  1
C)  2
D)  3E) A) and B)
F) A) and C)

Question 9

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

Accepted Answer

A)  A sigmatropic reaction is an intramolecular pericyclic reaction.
B)  In a sigmatropic reaction,s bond is broken in one of the reactants.
C)  The p bonds rearrange in a sigmatropic reaction.
D)  The number of p bonds in the reactants and product differs in a sigmatropic reaction.E) All of the above
F) None of the above

Question 10

What is the correct classification of the following reaction?

Accepted Answer

A)  Cycloaddition reaction
B)  Electrophilic reaction
C)  Electrocyclic reaction
D)  Sigmatropic reactionE) All of the above
F) None of the above

Question 11

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

Accepted Answer

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

Question 12

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 C)

Question 13

Which of the following statements about a p-bonding molecular orbital is true?

Accepted Answer

A)  A p-bonding molecular orbital is formed when two p orbitals of similar phase overlap.
B)  A p-bonding molecular orbital is lower in energy than a s-bonding molecular orbital.
C)  A p-bonding molecular orbital is formed when two p orbitals of opposite phase overlap.
D)  Both the statements a p-bonding molecular orbital is formed when two p orbitals of similar phase overlap and a p-bonding molecular orbital is lower in energy than a s-bonding molecular orbital are true.E) All of the above
F) None of the above

Question 14

Which of the following statements about a p* antibonding molecular orbital is true?

Accepted Answer

A)  A p* antibonding molecular orbital is formed when two p orbitals of similar phase overlap.
B)  A p* antibonding molecular orbital is formed when two p orbitals of opposite phase overlap.
C)  A p* antibonding molecular orbital is a higher-energy molecular orbital than a p bonding molecular orbital.
D)  Both the statements a p* antibonding molecular orbital is formed when two p orbitals of opposite phase overlap and a p* antibonding molecular orbital is a higher-energy molecular orbital than a p bonding molecular orbital are true.E) A) and D)
F) All of the above

Question 15

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

Accepted Answer

A)  3
B)  4
C)  5
D)  6E) A) and D)
F) A) and B)

Question 16

Which of the following statements about [2+2] cycloaddition reactions between two alkenes is true?

Accepted Answer

A)  The reaction is initiated by heat.
B)  The reaction is initiated by light.
C)  The product is a cyclopentane derivative.
D)  Each reactant contains two s electrons that participate in the formation of new bonds.E) All of the above
F) None of the above

Question 17

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

Accepted Answer

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

Question 18

What is the correct classification of the following reaction?

Accepted Answer

A)  Cycloaddition reaction
B)  Electrophilic reaction
C)  Electrocyclic reaction
D)  Sigmatropic reactionE) B) and C)
F) A) and D)

Question 19

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 20

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

Accepted Answer

A)  3
B)  4
C)  5
D)  6E) None of the above
F) B) and D)

Exam 25: Pericyclic Reactions

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

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

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

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Which of the following statements about [2+2] cycloaddition reactions between two alkenes is true?

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

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

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Which of the following statements about a p* antibonding molecular orbital is true?

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How many pi electrons are in the excited state HOMO for hexa-1,3,5-triene?

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What is the correct classification of the following reaction?

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Which of the following statements about a thermal reaction involving an even number of electron pairs is true?

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

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What type of cycloaddition reaction is shown below?

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

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What is the correct classification of the following reaction?

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How many pi electrons are in the excited state LUMO for hexa-1,3,5-triene?

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Which of the following statements about a p-bonding molecular orbital is 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 cycloaddition reactions is true?

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

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

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