The suprafacial or antarafacial stereochemistry of the following sigmatropic reaction by order [ x , y ] is, Concept introduction: A sigmatropic rearrangement is a process in which a sigma-bonded substituent atom or group migrates across a pie electron system from one position to another. So, A sigmatropic reaction in organic chemistry is a pericyclic reaction wherein the net result is one σ-bond is changed to another σ-bond. Sigmatropic rearrangements are concisely described by an order term [ i , j ], which is defined as the migration of a σ-bond adjacent to one or more π systems to a new position (i-1) and (j-1) atoms removed from the original location of the σ-bond. [3] When the sum of i and j is an even number, this is an indication of the involvement of a neutral, all C atom chain. An odd number is an indication of the involvement of a charged C atom or of a heteroatom lone pair replacing a C = C double bond. Thus, [1, 5] and [3, 3] shifts become [1, 4] and [2, 3] shifts with heteroatoms, while preserving symmetry considerations. If the migrating group remains on the same face of the π system, the shift is known as suprafacial, while if the migrating group transfers to the opposite face is called an antarafacial shift.

Question

Propose a mechanism for the following cycloaddition reaction. Classify the reaction using the [m + n] classifications for cycloadditions. Draw the bonding molecular orbitals and identify the type of bonding present (supra - supra, antaraantara, or supra - antara). Identify if this reaction would proceed thermally or photochemically.

Answer 1

Question

Chapter 30.7, Problem 7P

Interpretation Introduction

Interpretation:

The suprafacial or antarafacial stereochemistry of the following sigmatropic reaction by order [x, y] is,

Concept introduction:

A sigmatropic rearrangement is a process in which a sigma-bonded substituent atom or group migrates across a pie electron system from one position to another. So, A sigmatropic reaction in organic chemistry is a pericyclic reaction wherein the net result is one σ-bond is changed to another σ-bond.

Sigmatropic rearrangements are concisely described by an order term [i, j], which is defined as the migration of a σ-bond adjacent to one or more π systems to a new position (i-1) and (j-1) atoms removed from the original location of the σ-bond. [3] When the sum of i and j is an even number, this is an indication of the involvement of a neutral, all C atom chain. An odd number is an indication of the involvement of a charged C atom or of a heteroatom lone pair replacing a C = C double bond. Thus, [1, 5] and [3, 3] shifts become [1, 4] and [2, 3] shifts with heteroatoms, while preserving symmetry considerations.

If the migrating group remains on the same face of the π system, the shift is known as suprafacial, while if the migrating group transfers to the opposite face is called an antarafacial shift.

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