study guides for every class

that actually explain what's on your next test

Ylide Resonance

from class:

Organic Chemistry

Definition

Ylide resonance refers to the delocalization of electrons in a phosphorus-containing compound, known as a phosphorus ylide, which allows for the stabilization of the positive charge on the phosphorus atom and the negative charge on the adjacent atom. This resonance phenomenon is crucial in understanding the reactivity and behavior of phosphorus ylides, particularly in the context of the Wittig reaction.

congrats on reading the definition of Ylide Resonance. now let's actually learn it.

ok, let's learn stuff

5 Must Know Facts For Your Next Test

  1. Ylide resonance is essential for understanding the reactivity of phosphorus ylides in the Wittig reaction, as it allows for the stabilization of the positive charge on the phosphorus atom.
  2. The delocalization of electrons in a phosphorus ylide results in a more stable configuration, which is a key factor in the success of the Wittig reaction.
  3. Ylide resonance can be depicted using resonance structures, where the negative charge is shared between the carbon and the oxygen atoms, reducing the overall energy of the system.
  4. The ability of phosphorus ylides to participate in the Wittig reaction is directly related to their ylide resonance, as it enables the formation of the reactive intermediate.
  5. Understanding ylide resonance is crucial for predicting the outcome and selectivity of the Wittig reaction, as it influences the stability and reactivity of the phosphorus ylide.

Review Questions

  • Explain how ylide resonance contributes to the reactivity of phosphorus ylides in the Wittig reaction.
    • Ylide resonance is a key factor in the reactivity of phosphorus ylides in the Wittig reaction. The delocalization of electrons in the ylide structure allows for the stabilization of the positive charge on the phosphorus atom and the negative charge on the adjacent carbon atom. This resonance stabilization makes the phosphorus ylide a more reactive nucleophile, enabling it to effectively attack the carbonyl carbon of an aldehyde or ketone in the Wittig reaction. The stabilization of the ylide also helps to drive the formation of the reactive intermediate, which is a crucial step in the overall transformation.
  • Describe how the concept of ylide resonance can be used to predict the outcome and selectivity of the Wittig reaction.
    • Understanding ylide resonance is essential for predicting the outcome and selectivity of the Wittig reaction. The degree of resonance stabilization in the phosphorus ylide influences the stability and reactivity of the intermediate formed during the reaction. Highly resonance-stabilized ylides tend to be more selective, leading to the formation of the more thermodynamically stable alkene product. Conversely, less resonance-stabilized ylides may be less selective, potentially resulting in a mixture of alkene isomers. By considering the ylide resonance, chemists can anticipate the reactivity and selectivity of the Wittig reaction, allowing them to design and optimize the desired transformation.
  • Evaluate the role of ylide resonance in the mechanism of the Wittig reaction and explain how it contributes to the overall success of the transformation.
    • Ylide resonance is a crucial component of the mechanism of the Wittig reaction. The delocalization of electrons in the phosphorus ylide stabilizes the positive charge on the phosphorus atom and the negative charge on the adjacent carbon atom, creating a more reactive nucleophile. This resonance stabilization enables the ylide to effectively attack the carbonyl carbon of an aldehyde or ketone, forming a tetrahedral intermediate. The ylide resonance also helps to drive the elimination step, where the phosphine oxide is expelled, leading to the formation of the desired alkene product. Without the stabilizing effect of ylide resonance, the Wittig reaction would be much less efficient and selective, limiting its widespread use in organic synthesis. Therefore, the understanding and consideration of ylide resonance are essential for the successful application and optimization of the Wittig reaction.

"Ylide Resonance" also found in:

© 2024 Fiveable Inc. All rights reserved.
AP® and SAT® are trademarks registered by the College Board, which is not affiliated with, and does not endorse this website.
Glossary
Guides