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

1. Arrange the following in order of increasing bond energy (lowest bond energy first, highest bond energy last). Provide your rationale. C=C, C-F, C=C, C-N, C-C List the bond order for each example.

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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