Chapter 28, Problem 28.43AP

Interpretation Introduction

(a)

Interpretation:

When each of the compounds shown in Fig. P28.43 is heated in the presence of maleic anhydride, an inermediate is trapped as Diels-Alder adduct. The intermediate formed in each reaction, and its formation from the starting material are to be stated.

Concept introduction:

cycloaddition reaction can be referred as a reaction of two different π-electron systems to form a ring product. Notably, in this reaction two new sigma bonds are formed in product with the disappearance of two fewer π-bonds. In other words, cyclo addition reaction can be best described as the reaction of number of electrons involved. In [4+2] cycloaddition one component is having four electrons and other component is having two electrons.

Interpretation Introduction

(b)

Interpretation:

When each of the compounds shown in Fig. P28.43 is heated in the presence of maleic anhydride, an inermediate is trapped as Diels-Alder adduct. The intermediate formed in each reaction, and its formation from the starting material are to be stated.

Concept introduction:

Sigmatropic reaction can be described as the migration of allylic sigma bond at one end of the π-electron system to the other end of the π-electron system as an uncatalyzed intramolecular reaction. Though, the position of π-bond is changed in Sigmatropic reaction, the total number of π-bonds remain unchanged. The sigma bond can be cleaved at the middle or at the end of the π-system. The formation of sigma bond at 3, 3-position of a 1, 5-diene is called as cope rearrangement. Notably, [3, 3] sigmatropic reaction of allyl vinyl ether is termed as Claisen rearrangement.

Interpretation Introduction

(c)

Interpretation:

When each of the compounds shown in Fig. P28.43 is heated in the presence of maleic anhydride, an inermediate is trapped as Diels-Alder adduct. The intermediate formed in each reaction, and its formation from the starting material are to be stated.

Concept introduction:

Sigmatropic reaction can be described as the migration of allylic sigma bond at one end of the π-electron system to the other end of the π-electron system as an uncatalyzed intramolecular reaction. Though, the position of π-bond is changed in Sigmatropic reaction, the total number of π-bonds remain unchanged. The sigma bond can be cleaved at the middle or at the end of the π-system. The formation of sigma bond at 3, 3-position of a 1, 5-diene is called as cope rearrangement. Notably, [3, 3] sigmatropic reaction of allyl vinyl ether is termed as Claisen rearrangement.