Question 1

Which of the following statements about electrocyclic ring closure is not true?

Accepted Answer

A) It is an intramolecular reaction. 
B) It requires heat or light. 
C) The cyclic product contains one more s bond and one fewer p bond than the reactants. 
D) The cyclic product contains one more p bond and one fewer s bond than the reactants. 
A) It is an intramolecular reaction. 
B) It requires heat or light. 
C) The cyclic product contains one more s bond and one fewer p bond than the reactants. 
D) The cyclic product contains one more p bond and one fewer s bond than the reactants.

Question 2

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.

Question 3

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 4

Which of the following statements about sigmatropic rearrangements and orbital symmetry is not true?

Accepted Answer

A) Reactions involving six atoms or fewer must take place by suprafacial pathways. 
B) In a suprafacial rearrangement,the new s bond forms on the opposite side of the p system as the broken s bond. 
C) In an antarafacial rearrangement,the new s bond forms on the opposite side of the p system as the broken s bond. 
D) In a suprafacial rearrangement,the new s bond forms on the same side of the p system as the broken s bond. 
A) Reactions involving six atoms or fewer must take place by suprafacial pathways. 
B) In a suprafacial rearrangement,the new s bond forms on the opposite side of the p system as the broken s bond. 
C) In an antarafacial rearrangement,the new s bond forms on the opposite side of the p system as the broken s bond. 
D) In a suprafacial rearrangement,the new s bond forms on the same side of the p system as the broken s bond.

Question 5

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 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

How many pi electrons are in the ground state HOMO 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 8

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

Question 9

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 10

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.

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. 
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 12

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 13

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 14

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 15

How many bonding 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 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

Which of the following is a type of pericyclic reaction?

Accepted Answer

A) electrocyclic reactions 
B) acyclic reactions 
C) cycloelimination reactions 
D) electrophilic reactions 
A) electrocyclic reactions 
B) acyclic reactions 
C) cycloelimination reactions 
D) electrophilic reactions

Question 18

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

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 molecular orbitals is true?

Accepted Answer

A) The number of molecular orbitals formed is different from the number of atomic orbitals used. 
B) The number of molecular orbitals formed is equal to the number of atomic orbitals used. 
C) The number of molecular orbitals formed is equal to twice the number of atomic orbitals used. 
D) The number of molecular orbitals formed is equal to half the number of atomic orbitals used. 
A) The number of molecular orbitals formed is different from the number of atomic orbitals used. 
B) The number of molecular orbitals formed is equal to the number of atomic orbitals used. 
C) The number of molecular orbitals formed is equal to twice the number of atomic orbitals used. 
D) The number of molecular orbitals formed is equal to half the number of atomic orbitals used.

Question 20

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

Exam 25: Pericyclic Reactions

Which of the following statements about electrocyclic ring closure is not true?

Which of the following statements about cycloaddition reactions is true?

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

Which of the following statements about sigmatropic rearrangements and orbital symmetry is not true?

What is the organic product of the following electrocyclic reaction?

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

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

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

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

Which of the following statements about porbitals is true?

Which of the following statements about sigmatropic reactions is true?

What type of cycloaddition reaction is shown below?

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 Cope rearrangement?

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

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

Which of the following is a type of pericyclic reaction?

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

Which of the following statements about molecular orbitals is true?

How many bonding 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 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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