Question 1

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  bonds and one in a  bond.
D)   The Claisen rearrangement involves the rearrangement of an unsaturated ether to a ,-unsaturated carbonyl compound.

Question 2

Which of the following statements about cycloaddition reactions is true?

Accepted Answer

A)   Cycloaddition reactions occur only intermolecularly.
B)   Cycloaddition reactions occur only intramolecularly.
C)   Cycloaddition reactions form a cyclic product with two new  bonds.
D)   Cycloaddition reactions can be intramolecular or intermolecular.

Question 3

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 II

Question 4

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  bond forms on the opposite side of the  system as the broken  bond.
C)   In an antarafacial rearrangement, the new  bond forms on the opposite side of the  system as the broken  bond.
D)   In a suprafacial rearrangement, the new  bond forms on the same side of the  system as the broken  bond.

Question 5

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]

Question 6

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.

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.

Question 8

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

Accepted Answer

A)   4
B)   5
C)   10
D)   12

Question 9

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.

Question 10

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.

Question 11

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

Question 12

What type of sigmatropic rearrangement is illustrated below?

Accepted Answer

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

Question 13

What type of cycloaddition reaction is shown below?

Accepted Answer

A)   [2+2]
B)   [4+2]
C)   [4+4]
D)   [0+2]

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 II

Question 15

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

Accepted Answer

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

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 II

Question 17

Which of the following statements about the Cope rearrangement is not true?

Accepted Answer

A)   The Cope rearrangement involves the rearrangement of a 1,5-diene to an isomeric 1,5-diene.
B)   The Cope rearrangement takes place readily in a suprafacial pathway under photochemical conditions.
C)   The Cope rearrangement involves three electron pairs; two in  bonds and one in a  bond.
D)   The Cope rearrangement takes place readily in a suprafacial pathway, when heated.

Question 18

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

Question 19

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

Accepted Answer

A)   3
B)   4
C)   5
D)   6

Question 20

What type of sigmatropic rearrangement is illustrated below?

Accepted Answer

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

Exam 27: Pericyclic Reactions

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-hexatriene?

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

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Which of the following statements about the Cope rearrangement is not true?

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Which of the following statements about cycloaddition reactions is true?

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What type of cycloaddition reaction is shown below?

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

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Which of the following statements about sigmatropic rearrangements and orbital symmetry 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 is not a correct designation for a sigmatropic rearrangement?

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

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

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Which of the following statements about electrocyclic reactions is true?

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What type of sigmatropic rearrangement is illustrated below?

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Which of the following statements about pericyclic reactions is true?

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What type of sigmatropic rearrangement is illustrated below?

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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 a thermal reaction involving an even number of electron pairs is true?

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