Search results
Jan 23, 2023 · Molecular rearrangements in which a σ-bonded atom or group, flanked by one or more π-electron systems, shifts to a new location with a corresponding reorganization of the π-bonds are called sigmatropic reactions.
- Stereochemical Notations
Cycloaddition reactions and sigmatropic rearrangements both...
- Cope
The Cope rearrangement, not to be confused with the Cope...
- Ene Reactions
Contributors; The joining of a double or triple bond to an...
- Claisen Rearrangement
Mechanism; The Claisen rearrangement, not to be confused...
- Allene
The LibreTexts libraries are Powered by NICE CXone Expert...
- William Reusch
We would like to show you a description here but the site...
- Stereochemical Notations
Sigmatropic rearrangements are intramolecular reactions involving the migration of a sigma bond across a pi system. Examples include hydrogen atoms migrating across dienes upon heating (some even do this spontaneously at room temperature) and hydrogen atoms migrating across alkenes with light.
Sep 25, 2024 · This section covers sigmatropic rearrangements, a type of pericyclic reaction where sigma bonds break and reform while the molecular structure rearranges. The examples illustrate the mechanisms and …
Sigmatropic reactions often have transition-metal catalysts that form intermediates in analogous reactions. The most well-known of the sigmatropic rearrangements are the [3,3] Cope rearrangement, Claisen rearrangement, Carroll rearrangement, and the Fischer indole synthesis.
A sigmatropic rearrangement, the third general kind of pericyclic reaction, is a process in which a σ -bonded substituent atom or group migrates across a π electron system from one position to another. A σ bond is broken in the reactant, the π bonds move, and a new σ bond is formed in the product.
In fact, the [1,5] suprafacial shift of a hydrogen atom across two double bonds of a π system is a commonly observed sigmatropic rearrangements. For example, 5-methyl-1,3-cyclopentadiene rapidly rearranges at room temperature to yield a mixture of 1-methyl-, 2-methyl-, and 5-methyl-isomers.
People also ask
What are sigmatropic rearrangements?
Which sigmatropic rearrangements are reversible?
What are sigmatropic reactions?
Which two groups are connected by the bond in a sigmatropic rearrangement?
What is a sigmatropic rearrangement of an allylic vinylic ether?
Nov 19, 2016 · Sigmatropic rearrangements are another important class of pericyclic reactions, in which one sigma bonded atom or group is shifted from its allylic type position to the distant end of the adjacent π system followed by reorientation of the π electrons in the carbon skeletal system.
