Question 1

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

Accepted Answer

A) 0 
B) 1 
C) 2 
D) 3 
A) 0 
B) 1 
C) 2 
D) 3 A

Question 2

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. 
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. B

Question 3

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

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

Question 6

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

Question 7

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

Accepted Answer

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

Question 8

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. 
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.

Question 9

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

Accepted Answer

A) 0 
B) 2 
C) 4 
D) 6 
A) 0 
B) 2 
C) 4 
D) 6

Question 10

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

Accepted Answer

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

Question 11

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

Question 12

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. 
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.

Question 13

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

Accepted Answer

A) cycloadditions 
B) nucleophilic reactions 
C) electrocyclic reactions 
D) sigmatropic rearrangements 
A) cycloadditions 
B) nucleophilic reactions 
C) electrocyclic reactions 
D) sigmatropic rearrangements

Question 14

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

Question 15

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. 
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 16

What is the organic product of the following electrocyclic reaction?

Accepted Answer

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

Question 17

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. 
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.

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

Question 19

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

Question 20

What type of sigmatropic rearrangement is illustrated below?

Accepted Answer

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

Exam 25: Pericyclic Reactions

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

Which of the following statements about pericyclic reactions is true?

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

What type of sigmatropic rearrangement is illustrated below?

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

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

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

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

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

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

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

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

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

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

Which of the following statements about pericyclic reactions is true?

What is the organic product of the following electrocyclic reaction?

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

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

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

What type of sigmatropic rearrangement is illustrated below?

Structure and Bonding

Acids and Bases

Introduction to Organic Molecules and Functional Groups

Alkanes

Stereochemistry

Understanding Organic Reactions

Alkyl Halides and Nucleophilic Substitution

Alkyl Halides and Elimination Reactions

Alcohols,ethers,and Related Compounds

Alkenes and Addition Reactions

Alkynes and Synthesis

Oxidation and Reduction

Radical Reactions

Conjugation, resonance, and Dienes

Benzene and Aromatic Compounds

Reactions of Aromatic Compounds

Introduction to Carbonyl Chemistry; Organometallic Reagents; Oxidation and Reduction

Aldehydes and Ketones - Nucleophilic Addition

Carboxylic Acids and the Acidity of the O-H Bond

Carboxylic Acids and Their Derivatives - Nucleophilic Acyl Substitution

Substitution Reactions of Carbonyl Compounds at the a Carbon

Carbonyl Condensation Reactions

Amines

Carbon-Carbon Bond-Forming Reactions in Organic Synthesis

Carbohydrates

Amino Acids and Proteins

Synthetic Polymers

Lipids

Molecular Ion Peaks and Fragmentation Patterns

Analyzing Molecular Motion and Infrared Spectroscopy

Organic Spectroscopy Concepts

Filters