For each of the given thermal electrocyclic reactions, the major product formed should be determined. Concept introduction: Electrocyclic reaction is a concerted cyclization reaction of conjugated polyenes ( π-system ) , in which one π-bond is converted into an σ-bond and remaining π-bonds shift their positions. Thereby the newly formed σ-bond connects the two ends of π-system to form a ring. The mechanism of the ring formation in the Electrocyclic reaction is drawn by using arrows representing the forming σ-bond and the shifting of π-bonds in the π-system of a polyene. The reaction conditions (thermal or photochemical) controls the product in such a way that the rotation for end lobes ( ring closure ) of the HOMO of conjugated (π-system) polyene. According to Woodward-Hoffmann rule for thermal and photochemical Electrocyclic reactions , π-systems Thermal Photochemical 4- π-electrons Conrotatory Disrotatory 6- π-electrons Disrotatory Conrotatory The mechanism for reverse of Electrocyclic reaction is drawn by using arrows representing the conversion of σ-bond to π-bond and the shifting of π-bonds in the π-system of a cyclic alkene . To determine: the major product formed for each of the given thermal electrocyclic reactions.

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Answer 1

Question

Chapter 16.9, Problem 20CC

(a)

Interpretation Introduction

Interpretation:

For each of the given thermal electrocyclic reactions, the major product formed should be determined.

Concept introduction:

Electrocyclic reaction is a concerted cyclization reaction of conjugated polyenes (π-system), in which one π-bond is converted into an σ-bond and remaining π-bonds shift their positions. Thereby the newly formed σ-bond connects the two ends of π-system to form a ring.

The mechanism of the ring formation in the Electrocyclic reaction is drawn by using arrows representing the forming σ-bond and the shifting of π-bonds in the π-system of a polyene.

The reaction conditions (thermal or photochemical) controls the product in such a way that the rotation for end lobes (ring closure) of the HOMO of conjugated (π-system) polyene.

According to Woodward-Hoffmann rule for thermal and photochemical Electrocyclic reactions,

π-systems Thermal Photochemical
4- π-electrons Conrotatory Disrotatory
6- π-electrons Disrotatory Conrotatory

The mechanism for reverse of Electrocyclic reaction is drawn by using arrows representing the conversion of σ-bond to π-bond and the shifting of π-bonds in the π-system of a cyclic alkene.

To determine: the major product formed for each of the given thermal electrocyclic reactions.

(b)

Interpretation Introduction

Interpretation:

For each of the given thermal electrocyclic reactions, the major product formed should be determined.

Concept introduction:

Electrocyclic reaction is a concerted cyclization reaction of conjugated polyenes (π-system), in which one π-bond is converted into an σ-bond and remaining π-bonds shift their positions. Thereby the newly formed σ-bond connects the two ends of π-system to form a ring.

The mechanism of the ring formation in the Electrocyclic reaction is drawn by using arrows representing the forming σ-bond and the shifting of π-bonds in the π-system of a polyene.

The reaction conditions (thermal or photochemical) controls the product in such a way that the rotation for end lobes (ring closure) of the HOMO of conjugated (π-system) polyene.

According to Woodward-Hoffmann rule for thermal and photochemical Electrocyclic reactions,

π-systems Thermal Photochemical
4- π-electrons Conrotatory Disrotatory
6- π-electrons Disrotatory Conrotatory

The mechanism for reverse of Electrocyclic reaction is drawn by using arrows representing the conversion of σ-bond to π-bond and the shifting of π-bonds in the π-system of a cyclic alkene.

To determine: the major product formed for each of the given thermal electrocyclic reactions.

(c)

Interpretation Introduction

Interpretation:

For each of the given thermal electrocyclic reactions, the major product formed should be determined.

Concept introduction:

Electrocyclic reaction is a concerted cyclization reaction of conjugated polyenes (π-system), in which one π-bond is converted into an σ-bond and remaining π-bonds shift their positions. Thereby the newly formed σ-bond connects the two ends of π-system to form a ring.

The mechanism of the ring formation in the Electrocyclic reaction is drawn by using arrows representing the forming σ-bond and the shifting of π-bonds in the π-system of a polyene.

The reaction conditions (thermal or photochemical) controls the product in such a way that the rotation for end lobes (ring closure) of the HOMO of conjugated (π-system) polyene.

According to Woodward-Hoffmann rule for thermal and photochemical Electrocyclic reactions,

π-systems Thermal Photochemical
4- π-electrons Conrotatory Disrotatory
6- π-electrons Disrotatory Conrotatory

The mechanism for reverse of Electrocyclic reaction is drawn by using arrows representing the conversion of σ-bond to π-bond and the shifting of π-bonds in the π-system of a cyclic alkene.

To determine: the major product formed for each of the given thermal electrocyclic reactions.

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Answer 2

Question

Chapter 16.9, Problem 20CC

(a)

Interpretation Introduction

Interpretation:

For each of the given thermal electrocyclic reactions, the major product formed should be determined.

Concept introduction:

Electrocyclic reaction is a concerted cyclization reaction of conjugated polyenes (π-system), in which one π-bond is converted into an σ-bond and remaining π-bonds shift their positions. Thereby the newly formed σ-bond connects the two ends of π-system to form a ring.

The mechanism of the ring formation in the Electrocyclic reaction is drawn by using arrows representing the forming σ-bond and the shifting of π-bonds in the π-system of a polyene.

The reaction conditions (thermal or photochemical) controls the product in such a way that the rotation for end lobes (ring closure) of the HOMO of conjugated (π-system) polyene.

According to Woodward-Hoffmann rule for thermal and photochemical Electrocyclic reactions,

π-systems Thermal Photochemical
4- π-electrons Conrotatory Disrotatory
6- π-electrons Disrotatory Conrotatory

The mechanism for reverse of Electrocyclic reaction is drawn by using arrows representing the conversion of σ-bond to π-bond and the shifting of π-bonds in the π-system of a cyclic alkene.

To determine: the major product formed for each of the given thermal electrocyclic reactions.

(b)

Interpretation Introduction

Interpretation:

For each of the given thermal electrocyclic reactions, the major product formed should be determined.

Concept introduction:

Electrocyclic reaction is a concerted cyclization reaction of conjugated polyenes (π-system), in which one π-bond is converted into an σ-bond and remaining π-bonds shift their positions. Thereby the newly formed σ-bond connects the two ends of π-system to form a ring.

The mechanism of the ring formation in the Electrocyclic reaction is drawn by using arrows representing the forming σ-bond and the shifting of π-bonds in the π-system of a polyene.

The reaction conditions (thermal or photochemical) controls the product in such a way that the rotation for end lobes (ring closure) of the HOMO of conjugated (π-system) polyene.

According to Woodward-Hoffmann rule for thermal and photochemical Electrocyclic reactions,

π-systems Thermal Photochemical
4- π-electrons Conrotatory Disrotatory
6- π-electrons Disrotatory Conrotatory

The mechanism for reverse of Electrocyclic reaction is drawn by using arrows representing the conversion of σ-bond to π-bond and the shifting of π-bonds in the π-system of a cyclic alkene.

To determine: the major product formed for each of the given thermal electrocyclic reactions.

(c)

Interpretation Introduction

Interpretation:

For each of the given thermal electrocyclic reactions, the major product formed should be determined.

Concept introduction:

Electrocyclic reaction is a concerted cyclization reaction of conjugated polyenes (π-system), in which one π-bond is converted into an σ-bond and remaining π-bonds shift their positions. Thereby the newly formed σ-bond connects the two ends of π-system to form a ring.

The mechanism of the ring formation in the Electrocyclic reaction is drawn by using arrows representing the forming σ-bond and the shifting of π-bonds in the π-system of a polyene.

The reaction conditions (thermal or photochemical) controls the product in such a way that the rotation for end lobes (ring closure) of the HOMO of conjugated (π-system) polyene.

According to Woodward-Hoffmann rule for thermal and photochemical Electrocyclic reactions,

π-systems Thermal Photochemical
4- π-electrons Conrotatory Disrotatory
6- π-electrons Disrotatory Conrotatory

The mechanism for reverse of Electrocyclic reaction is drawn by using arrows representing the conversion of σ-bond to π-bond and the shifting of π-bonds in the π-system of a cyclic alkene.

To determine: the major product formed for each of the given thermal electrocyclic reactions.

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Answer 3

Question

Chapter 16.9, Problem 20CC

(a)

Interpretation Introduction

Interpretation:

For each of the given thermal electrocyclic reactions, the major product formed should be determined.

Concept introduction:

Electrocyclic reaction is a concerted cyclization reaction of conjugated polyenes (π-system), in which one π-bond is converted into an σ-bond and remaining π-bonds shift their positions. Thereby the newly formed σ-bond connects the two ends of π-system to form a ring.

The mechanism of the ring formation in the Electrocyclic reaction is drawn by using arrows representing the forming σ-bond and the shifting of π-bonds in the π-system of a polyene.

The reaction conditions (thermal or photochemical) controls the product in such a way that the rotation for end lobes (ring closure) of the HOMO of conjugated (π-system) polyene.

According to Woodward-Hoffmann rule for thermal and photochemical Electrocyclic reactions,

π-systems Thermal Photochemical
4- π-electrons Conrotatory Disrotatory
6- π-electrons Disrotatory Conrotatory

The mechanism for reverse of Electrocyclic reaction is drawn by using arrows representing the conversion of σ-bond to π-bond and the shifting of π-bonds in the π-system of a cyclic alkene.

To determine: the major product formed for each of the given thermal electrocyclic reactions.

(b)

Interpretation Introduction

Interpretation:

For each of the given thermal electrocyclic reactions, the major product formed should be determined.

Concept introduction:

Electrocyclic reaction is a concerted cyclization reaction of conjugated polyenes (π-system), in which one π-bond is converted into an σ-bond and remaining π-bonds shift their positions. Thereby the newly formed σ-bond connects the two ends of π-system to form a ring.

The mechanism of the ring formation in the Electrocyclic reaction is drawn by using arrows representing the forming σ-bond and the shifting of π-bonds in the π-system of a polyene.

The reaction conditions (thermal or photochemical) controls the product in such a way that the rotation for end lobes (ring closure) of the HOMO of conjugated (π-system) polyene.

According to Woodward-Hoffmann rule for thermal and photochemical Electrocyclic reactions,

π-systems Thermal Photochemical
4- π-electrons Conrotatory Disrotatory
6- π-electrons Disrotatory Conrotatory

The mechanism for reverse of Electrocyclic reaction is drawn by using arrows representing the conversion of σ-bond to π-bond and the shifting of π-bonds in the π-system of a cyclic alkene.

To determine: the major product formed for each of the given thermal electrocyclic reactions.

(c)

Interpretation Introduction

Interpretation:

For each of the given thermal electrocyclic reactions, the major product formed should be determined.

Concept introduction:

Electrocyclic reaction is a concerted cyclization reaction of conjugated polyenes (π-system), in which one π-bond is converted into an σ-bond and remaining π-bonds shift their positions. Thereby the newly formed σ-bond connects the two ends of π-system to form a ring.

The mechanism of the ring formation in the Electrocyclic reaction is drawn by using arrows representing the forming σ-bond and the shifting of π-bonds in the π-system of a polyene.

The reaction conditions (thermal or photochemical) controls the product in such a way that the rotation for end lobes (ring closure) of the HOMO of conjugated (π-system) polyene.

According to Woodward-Hoffmann rule for thermal and photochemical Electrocyclic reactions,

π-systems Thermal Photochemical
4- π-electrons Conrotatory Disrotatory
6- π-electrons Disrotatory Conrotatory

The mechanism for reverse of Electrocyclic reaction is drawn by using arrows representing the conversion of σ-bond to π-bond and the shifting of π-bonds in the π-system of a cyclic alkene.

To determine: the major product formed for each of the given thermal electrocyclic reactions.

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Answer 4

Question

Chapter 16.9, Problem 20CC

(a)

Interpretation Introduction

Interpretation:

For each of the given thermal electrocyclic reactions, the major product formed should be determined.

Concept introduction:

Electrocyclic reaction is a concerted cyclization reaction of conjugated polyenes (π-system), in which one π-bond is converted into an σ-bond and remaining π-bonds shift their positions. Thereby the newly formed σ-bond connects the two ends of π-system to form a ring.

The mechanism of the ring formation in the Electrocyclic reaction is drawn by using arrows representing the forming σ-bond and the shifting of π-bonds in the π-system of a polyene.

The reaction conditions (thermal or photochemical) controls the product in such a way that the rotation for end lobes (ring closure) of the HOMO of conjugated (π-system) polyene.

According to Woodward-Hoffmann rule for thermal and photochemical Electrocyclic reactions,

π-systems Thermal Photochemical
4- π-electrons Conrotatory Disrotatory
6- π-electrons Disrotatory Conrotatory

The mechanism for reverse of Electrocyclic reaction is drawn by using arrows representing the conversion of σ-bond to π-bond and the shifting of π-bonds in the π-system of a cyclic alkene.

To determine: the major product formed for each of the given thermal electrocyclic reactions.

(b)

Interpretation Introduction

Interpretation:

For each of the given thermal electrocyclic reactions, the major product formed should be determined.

Concept introduction:

Electrocyclic reaction is a concerted cyclization reaction of conjugated polyenes (π-system), in which one π-bond is converted into an σ-bond and remaining π-bonds shift their positions. Thereby the newly formed σ-bond connects the two ends of π-system to form a ring.

The mechanism of the ring formation in the Electrocyclic reaction is drawn by using arrows representing the forming σ-bond and the shifting of π-bonds in the π-system of a polyene.

The reaction conditions (thermal or photochemical) controls the product in such a way that the rotation for end lobes (ring closure) of the HOMO of conjugated (π-system) polyene.

According to Woodward-Hoffmann rule for thermal and photochemical Electrocyclic reactions,

π-systems Thermal Photochemical
4- π-electrons Conrotatory Disrotatory
6- π-electrons Disrotatory Conrotatory

The mechanism for reverse of Electrocyclic reaction is drawn by using arrows representing the conversion of σ-bond to π-bond and the shifting of π-bonds in the π-system of a cyclic alkene.

To determine: the major product formed for each of the given thermal electrocyclic reactions.

(c)

Interpretation Introduction

Interpretation:

For each of the given thermal electrocyclic reactions, the major product formed should be determined.

Concept introduction:

Electrocyclic reaction is a concerted cyclization reaction of conjugated polyenes (π-system), in which one π-bond is converted into an σ-bond and remaining π-bonds shift their positions. Thereby the newly formed σ-bond connects the two ends of π-system to form a ring.

The mechanism of the ring formation in the Electrocyclic reaction is drawn by using arrows representing the forming σ-bond and the shifting of π-bonds in the π-system of a polyene.

The reaction conditions (thermal or photochemical) controls the product in such a way that the rotation for end lobes (ring closure) of the HOMO of conjugated (π-system) polyene.

According to Woodward-Hoffmann rule for thermal and photochemical Electrocyclic reactions,

π-systems Thermal Photochemical
4- π-electrons Conrotatory Disrotatory
6- π-electrons Disrotatory Conrotatory

The mechanism for reverse of Electrocyclic reaction is drawn by using arrows representing the conversion of σ-bond to π-bond and the shifting of π-bonds in the π-system of a cyclic alkene.

To determine: the major product formed for each of the given thermal electrocyclic reactions.

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Answer 5

Chapter 16.9, Problem 20CC

(a)

Interpretation Introduction

Interpretation:

For each of the given thermal electrocyclic reactions, the major product formed should be determined.

Concept introduction:

Electrocyclic reaction is a concerted cyclization reaction of conjugated polyenes (π-system), in which one π-bond is converted into an σ-bond and remaining π-bonds shift their positions. Thereby the newly formed σ-bond connects the two ends of π-system to form a ring.

The mechanism of the ring formation in the Electrocyclic reaction is drawn by using arrows representing the forming σ-bond and the shifting of π-bonds in the π-system of a polyene.

The reaction conditions (thermal or photochemical) controls the product in such a way that the rotation for end lobes (ring closure) of the HOMO of conjugated (π-system) polyene.

According to Woodward-Hoffmann rule for thermal and photochemical Electrocyclic reactions,

π-systems Thermal Photochemical
4- π-electrons Conrotatory Disrotatory
6- π-electrons Disrotatory Conrotatory

The mechanism for reverse of Electrocyclic reaction is drawn by using arrows representing the conversion of σ-bond to π-bond and the shifting of π-bonds in the π-system of a cyclic alkene.

To determine: the major product formed for each of the given thermal electrocyclic reactions.

(b)

Interpretation Introduction

Interpretation:

For each of the given thermal electrocyclic reactions, the major product formed should be determined.

Concept introduction:

Electrocyclic reaction is a concerted cyclization reaction of conjugated polyenes (π-system), in which one π-bond is converted into an σ-bond and remaining π-bonds shift their positions. Thereby the newly formed σ-bond connects the two ends of π-system to form a ring.

The mechanism of the ring formation in the Electrocyclic reaction is drawn by using arrows representing the forming σ-bond and the shifting of π-bonds in the π-system of a polyene.

The reaction conditions (thermal or photochemical) controls the product in such a way that the rotation for end lobes (ring closure) of the HOMO of conjugated (π-system) polyene.

According to Woodward-Hoffmann rule for thermal and photochemical Electrocyclic reactions,

π-systems Thermal Photochemical
4- π-electrons Conrotatory Disrotatory
6- π-electrons Disrotatory Conrotatory

The mechanism for reverse of Electrocyclic reaction is drawn by using arrows representing the conversion of σ-bond to π-bond and the shifting of π-bonds in the π-system of a cyclic alkene.

To determine: the major product formed for each of the given thermal electrocyclic reactions.

(c)

Interpretation Introduction

Interpretation:

For each of the given thermal electrocyclic reactions, the major product formed should be determined.

Concept introduction:

Electrocyclic reaction is a concerted cyclization reaction of conjugated polyenes (π-system), in which one π-bond is converted into an σ-bond and remaining π-bonds shift their positions. Thereby the newly formed σ-bond connects the two ends of π-system to form a ring.

The mechanism of the ring formation in the Electrocyclic reaction is drawn by using arrows representing the forming σ-bond and the shifting of π-bonds in the π-system of a polyene.

The reaction conditions (thermal or photochemical) controls the product in such a way that the rotation for end lobes (ring closure) of the HOMO of conjugated (π-system) polyene.

According to Woodward-Hoffmann rule for thermal and photochemical Electrocyclic reactions,

π-systems Thermal Photochemical
4- π-electrons Conrotatory Disrotatory
6- π-electrons Disrotatory Conrotatory

The mechanism for reverse of Electrocyclic reaction is drawn by using arrows representing the conversion of σ-bond to π-bond and the shifting of π-bonds in the π-system of a cyclic alkene.

To determine: the major product formed for each of the given thermal electrocyclic reactions.

Answer 6

Chapter 16.9, Problem 20CC

(a)

Interpretation Introduction

Interpretation:

For each of the given thermal electrocyclic reactions, the major product formed should be determined.

Concept introduction:

Electrocyclic reaction is a concerted cyclization reaction of conjugated polyenes (π-system), in which one π-bond is converted into an σ-bond and remaining π-bonds shift their positions. Thereby the newly formed σ-bond connects the two ends of π-system to form a ring.

The mechanism of the ring formation in the Electrocyclic reaction is drawn by using arrows representing the forming σ-bond and the shifting of π-bonds in the π-system of a polyene.

The reaction conditions (thermal or photochemical) controls the product in such a way that the rotation for end lobes (ring closure) of the HOMO of conjugated (π-system) polyene.

According to Woodward-Hoffmann rule for thermal and photochemical Electrocyclic reactions,

π-systems Thermal Photochemical
4- π-electrons Conrotatory Disrotatory
6- π-electrons Disrotatory Conrotatory

The mechanism for reverse of Electrocyclic reaction is drawn by using arrows representing the conversion of σ-bond to π-bond and the shifting of π-bonds in the π-system of a cyclic alkene.

To determine: the major product formed for each of the given thermal electrocyclic reactions.

Answer 7

Chapter 16.9, Problem 20CC

(a)

Interpretation Introduction

Interpretation:

For each of the given thermal electrocyclic reactions, the major product formed should be determined.

Concept introduction:

Electrocyclic reaction is a concerted cyclization reaction of conjugated polyenes (π-system), in which one π-bond is converted into an σ-bond and remaining π-bonds shift their positions. Thereby the newly formed σ-bond connects the two ends of π-system to form a ring.

The mechanism of the ring formation in the Electrocyclic reaction is drawn by using arrows representing the forming σ-bond and the shifting of π-bonds in the π-system of a polyene.

The reaction conditions (thermal or photochemical) controls the product in such a way that the rotation for end lobes (ring closure) of the HOMO of conjugated (π-system) polyene.

According to Woodward-Hoffmann rule for thermal and photochemical Electrocyclic reactions,

π-systems Thermal Photochemical
4- π-electrons Conrotatory Disrotatory
6- π-electrons Disrotatory Conrotatory

The mechanism for reverse of Electrocyclic reaction is drawn by using arrows representing the conversion of σ-bond to π-bond and the shifting of π-bonds in the π-system of a cyclic alkene.

To determine: the major product formed for each of the given thermal electrocyclic reactions.

Answer 8

(b)

Interpretation Introduction

Interpretation:

For each of the given thermal electrocyclic reactions, the major product formed should be determined.

Concept introduction:

Electrocyclic reaction is a concerted cyclization reaction of conjugated polyenes (π-system), in which one π-bond is converted into an σ-bond and remaining π-bonds shift their positions. Thereby the newly formed σ-bond connects the two ends of π-system to form a ring.

The mechanism of the ring formation in the Electrocyclic reaction is drawn by using arrows representing the forming σ-bond and the shifting of π-bonds in the π-system of a polyene.

The reaction conditions (thermal or photochemical) controls the product in such a way that the rotation for end lobes (ring closure) of the HOMO of conjugated (π-system) polyene.

According to Woodward-Hoffmann rule for thermal and photochemical Electrocyclic reactions,

π-systems Thermal Photochemical
4- π-electrons Conrotatory Disrotatory
6- π-electrons Disrotatory Conrotatory

The mechanism for reverse of Electrocyclic reaction is drawn by using arrows representing the conversion of σ-bond to π-bond and the shifting of π-bonds in the π-system of a cyclic alkene.

To determine: the major product formed for each of the given thermal electrocyclic reactions.

Answer 9

(b)

Interpretation Introduction

Interpretation:

For each of the given thermal electrocyclic reactions, the major product formed should be determined.

Concept introduction:

Electrocyclic reaction is a concerted cyclization reaction of conjugated polyenes (π-system), in which one π-bond is converted into an σ-bond and remaining π-bonds shift their positions. Thereby the newly formed σ-bond connects the two ends of π-system to form a ring.

The mechanism of the ring formation in the Electrocyclic reaction is drawn by using arrows representing the forming σ-bond and the shifting of π-bonds in the π-system of a polyene.

The reaction conditions (thermal or photochemical) controls the product in such a way that the rotation for end lobes (ring closure) of the HOMO of conjugated (π-system) polyene.

According to Woodward-Hoffmann rule for thermal and photochemical Electrocyclic reactions,

π-systems Thermal Photochemical
4- π-electrons Conrotatory Disrotatory
6- π-electrons Disrotatory Conrotatory

The mechanism for reverse of Electrocyclic reaction is drawn by using arrows representing the conversion of σ-bond to π-bond and the shifting of π-bonds in the π-system of a cyclic alkene.

To determine: the major product formed for each of the given thermal electrocyclic reactions.

Answer 10

(c)

Interpretation Introduction

Interpretation:

For each of the given thermal electrocyclic reactions, the major product formed should be determined.

Concept introduction:

Electrocyclic reaction is a concerted cyclization reaction of conjugated polyenes (π-system), in which one π-bond is converted into an σ-bond and remaining π-bonds shift their positions. Thereby the newly formed σ-bond connects the two ends of π-system to form a ring.

The mechanism of the ring formation in the Electrocyclic reaction is drawn by using arrows representing the forming σ-bond and the shifting of π-bonds in the π-system of a polyene.

The reaction conditions (thermal or photochemical) controls the product in such a way that the rotation for end lobes (ring closure) of the HOMO of conjugated (π-system) polyene.

According to Woodward-Hoffmann rule for thermal and photochemical Electrocyclic reactions,

π-systems Thermal Photochemical
4- π-electrons Conrotatory Disrotatory
6- π-electrons Disrotatory Conrotatory

The mechanism for reverse of Electrocyclic reaction is drawn by using arrows representing the conversion of σ-bond to π-bond and the shifting of π-bonds in the π-system of a cyclic alkene.

To determine: the major product formed for each of the given thermal electrocyclic reactions.

Answer 11

(c)

Interpretation Introduction

Interpretation:

For each of the given thermal electrocyclic reactions, the major product formed should be determined.

Concept introduction:

Electrocyclic reaction is a concerted cyclization reaction of conjugated polyenes (π-system), in which one π-bond is converted into an σ-bond and remaining π-bonds shift their positions. Thereby the newly formed σ-bond connects the two ends of π-system to form a ring.

The mechanism of the ring formation in the Electrocyclic reaction is drawn by using arrows representing the forming σ-bond and the shifting of π-bonds in the π-system of a polyene.

The reaction conditions (thermal or photochemical) controls the product in such a way that the rotation for end lobes (ring closure) of the HOMO of conjugated (π-system) polyene.

According to Woodward-Hoffmann rule for thermal and photochemical Electrocyclic reactions,

π-systems Thermal Photochemical
4- π-electrons Conrotatory Disrotatory
6- π-electrons Disrotatory Conrotatory

The mechanism for reverse of Electrocyclic reaction is drawn by using arrows representing the conversion of σ-bond to π-bond and the shifting of π-bonds in the π-system of a cyclic alkene.

To determine: the major product formed for each of the given thermal electrocyclic reactions.

Answer 12

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Answer 13

Expert Solution & Answer

Answer 14

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Answer 15

Ch. 16.1 - Prob. 1CC Ch. 16.2 - Prob. 2CC Ch. 16.2 - Prob. 3CC Ch. 16.2 - Prob. 4CC Ch. 16.3 - Prob. 5CC Ch. 16.4 - Prob. 1LTS Ch. 16.4 - Prob. 6PTS Ch. 16.4 - Prob. 7PTS Ch. 16.4 - Prob. 8ATS Ch. 16.5 - Prob. 2LTS

π-systems	Thermal	Photochemical
4- π-electrons	Conrotatory	Disrotatory
6- π-electrons	Disrotatory	Conrotatory

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Chapter 16 Solutions