Question 1

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

Accepted Answer

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

Question 2

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

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 IIE) C) and D)
F) B) and D)

Question 4

What type of sigmatropic rearrangement is illustrated below?

Accepted Answer

A)  [1,3]
B)  [1,4]
C)  [3,3]
D)  [1,5]E) None of the above
F) B) and C)

Question 5

Why is the Diels-Alder reaction called a thermal [4+2] cycloaddition?

Accepted Answer

A)  Because the reaction is initiated by heat; the diene has four p electrons and the dienophile has two p electrons.
B)  Because the reaction is initiated by light; the diene has four p electrons and the dienophile has two p electrons.
C)  Because the reaction is initiated by heat; the dienophile has four p electrons and the diene has two pelectrons.
D)  Because the reaction is initiated by light; the dienophile has four p electrons and the diene has two pelectrons.E) A) and D)
F) None of the above

Question 6

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

Accepted Answer

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

Question 7

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) None of the above

Question 8

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

Question 9

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

Question 10

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

Accepted Answer

A)  cycloadditions
B)  nucleophilic reactions
C)  electrocyclic reactions
D)  sigmatropic rearrangementsE) All of the above
F) A) and B)

Question 11

Which of the following statements about sigmatropic reactions is true?

Accepted Answer

A)  The reactants contain one more p bond than the product.
B)  The product contains one more p bond than the reactant.
C)  A p bond is broken in the reactant.
D)  A s bond is broken in the reactant.E) All of the above
F) A) and B)

Question 12

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) A) and D)

Question 13

What type of sigmatropic rearrangement is illustrated below?

Accepted Answer

A)  [1,3]
B)  [1,4]
C)  [3,3]
D)  [1,5]E) All of the above
F) C) and D)

Question 14

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

Question 15

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) A) and B)

Question 16

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

Accepted Answer

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

Question 17

Which of the following statements about porbitals is true?

Accepted Answer

A)  P Orbitals are formed by the linear combination of two sp3 orbitals.
B)  P Orbitals are formed by the linear combination of two sp2 orbitals.
C)  P Orbitals are formed by the linear combination of two sp orbitals.
D)  P Orbitals are formed by the linear combination of two p orbitals.E) A) and C)
F) C) and D) D

Question 18

How many nodes are present in Y5 of 1,3,5,7,9-decapentaene?

Accepted Answer

A)  2
B)  3
C)  4
D)  5E) A) and B)
F) B) and D)

Question 19

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 p bonds.
D)  Cycloaddition reactions can be intramolecular or intermolecular.E) None of the above
F) B) and C) D

Question 20

Which of the following statements about an electrocyclic ring-opening reaction is not true?

Accepted Answer

A)  An electrocyclic ring-opening reaction is an intramolecular reaction.
B)  An electrocyclic ring-opening reaction requires a source of energy (heat or light) .
C)  The product of an electrocyclic ring-opening reaction contains one fewer p bond than the reactant.
D)  The product of an electrocyclic ring-opening reaction contains one more p bond than the reactant.E) A) and D)
F) All of the above

Exam 27: Pericyclic Reactions

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

Correct AnswerverifiedB

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

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

What type of sigmatropic rearrangement is illustrated below?

Correct AnswerverifiedShow Answer

Why is the Diels-Alder reaction called a thermal [4+2] cycloaddition?

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

Which of the following statements about sigmatropic reactions is true?

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

What type of sigmatropic rearrangement is illustrated below?

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

Which of the following statements about porbitals is true?

Correct AnswerverifiedD

How many nodes are present in Y5 of 1,3,5,7,9-decapentaene?

Correct AnswerverifiedShow Answer

Which of the following statements about cycloaddition reactions is true?

Correct AnswerverifiedD

Which of the following statements about an electrocyclic ring-opening reaction is not true?

Correct AnswerverifiedShow Answer

Correct Answer
verified
B

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified
D

How many nodes are present in Y₅ of 1,3,5,7,9-decapentaene?

Correct Answer
verified

Correct Answer
verified
D

Correct Answer
verified