Organic Chemistry
Organic Chemistry
2nd Edition
ISBN: 9781118452288
Author: David R. Klein
Publisher: WILEY
Question
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Chapter 17.9, Problem 24ATS

(a)

Interpretation Introduction

Interpretation:

For the given reactions, the product formed should be explained whether it is meso- compound or a pair of enantiomers.

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
  • Meso-compound is superimposable to its mirror image.
  • Enantiomers are the non-superimposable mirror images of each other.

To explain: the product formed is meso compound or a pair of enantiomers for each of the given reactions.

(b)

Interpretation Introduction

Interpretation:

For the given reactions, the product formed should be explained whether it is meso- compound or a pair of enantiomers.

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
  • Meso-compound is superimposable to its mirror image.
  • Enantiomers are the non-superimposable mirror images of each other.

To explain: the product formed is meso compound or a pair of enantiomers for each of the given reactions.

(c)

Interpretation Introduction

Interpretation:

For the given reactions, the product formed should be explained whether it is meso- compound or a pair of enantiomers.

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
  • Meso-compound is superimposable to its mirror image.
  • Enantiomers are the non-superimposable mirror images of each other.

To explain: the product formed is meso compound or a pair of enantiomers for each of the given reactions.

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Chapter 17 Solutions

Organic Chemistry

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