Question 1

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. 
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.

Question 2

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 3

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

Accepted Answer

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

Question 4

What type of cycloaddition reaction is shown below?

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 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 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. 
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 7

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 8

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 9

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 10

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. 
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.

Question 11

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. 
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.

Question 12

What is the correct classification of the following reaction?

Accepted Answer

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

Question 13

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 14

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

Question 15

What is the correct classification of the following reaction?

Accepted Answer

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

Question 16

How many pi electrons are in the ground state HOMO 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 bonding 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 18

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 19

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. 
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.

Question 20

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. 
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.

Exam 25: Pericyclic Reactions

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

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

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

What type of cycloaddition reaction is shown below?

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

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

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

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

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

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

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

What is the correct classification of the following reaction?

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

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

What is the correct classification of the following reaction?

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

How many bonding 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?

Which of the following statements about cycloaddition reactions is true?

Which of the following statements about cycloaddition reactions is not 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

Molecular Ion Peaks and Fragmentation Patterns

Analyzing Molecular Motion and Infrared Spectroscopy

Organic Spectroscopy Concepts

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