Question 1

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. 
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. D

Question 2

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. 
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. B

Question 3

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. 
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. D

Question 4

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. 
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.

Question 5

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 6

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 7

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 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

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 10

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 11

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

Question 13

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 14

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. 
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.

Question 15

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 16

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 17

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

Accepted Answer

A) 2 
B) 3 
C) 4 
D) 5 
A) 2 
B) 3 
C) 4 
D) 5

Question 18

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 19

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 20

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

Exam 27: Pericyclic Reactions

Which of the following statements about porbitals is true?

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

Which of the following statements about cycloaddition reactions is true?

Which of the following statements about sigmatropic reactions is true?

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

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

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

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

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

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

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

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

What type of sigmatropic rearrangement is illustrated below?

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

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

What type of sigmatropic rearrangement is illustrated below?

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

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

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

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

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

Alkynes

Oxidation and Reduction

Mass Spectrometry and Infrared Spectroscopy

Nuclear Magnetic Resonance Spectroscopy

Radical Reactions

Conjugation, Resonance, and Dienes

Benzene and Aromatic Compounds

Reactions of Aromatic Compounds

Carboxylic Acids and the Acidity of the O-H Bond

Introduction to Carbonyl Chemistry;

Aldehydes and Ketones Nucleophilic Addition

Carboxylic Acids and Derivatives

Substitution Reactions of Carbonyl Compounds at the Alpha-Carbon

Carbonyl Condensation Reactions

Amines

Carbon-Carbon Bond Forming Reactions in Organic Synthesis

Carbohydrates

Amino Acids and Proteins

Synthetic Polymers

Lipids

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