Question 1

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

Accepted Answer

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

Question 2

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

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

Question 4

What is the correct classification of the following reaction?

Accepted Answer

A) Cycloaddition reaction 
B) Electrocyclic reaction 
C) Electrophilic reaction 
D) Sigmatropic reaction 
A) Cycloaddition reaction 
B) Electrocyclic reaction 
C) Electrophilic reaction 
D) Sigmatropic reaction

Question 5

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. 
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.

Question 6

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.

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. 
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

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

Accepted Answer

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

Question 9

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 10

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 11

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 12

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 p electrons. 
D) Because the reaction is initiated by light; the dienophile has four p electrons and the diene has two p electrons. 
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 p electrons. 
D) Because the reaction is initiated by light; the dienophile has four p electrons and the diene has two p electrons.

Question 13

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 p bonds and one in a s bond. 
D) The Cope rearrangement takes place readily in a suprafacial pathway,when heated. 
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 p bonds and one in a s bond. 
D) The Cope rearrangement takes place readily in a suprafacial pathway,when heated.

Question 14

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. 
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 15

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 16

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 17

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

Accepted Answer

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

Question 18

What is the correct classification of the following reaction?

Accepted Answer

A) Cycloaddition reaction 
B) Electrocyclic reaction 
C) Electrophilic reaction 
D) Sigmatropic reaction 
A) Cycloaddition reaction 
B) Electrocyclic reaction 
C) Electrophilic reaction 
D) Sigmatropic reaction

Question 19

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

Question 20

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.

Exam 25: Pericyclic Reactions

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

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

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

What is the correct classification of the following reaction?

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

Which of the following statements about pericyclic reactions is true?

Which of the following statements about pericyclic reactions is true?

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

What type of sigmatropic rearrangement is illustrated below?

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

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

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

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

Which of the following statements about electrocyclic reactions is true?

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

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

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

What is the correct classification of the following reaction?

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

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

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

Spectroscopy A: Mass Spectrometry

Spectroscopy B: Infrared Spectroscopy

Spectroscopy C: Nuclear Magnetic Resonance Spectroscopy

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