Metathesis

Definition

Metathesis is a type of organic reaction where two molecules exchange parts, typically involving the rearrangement of chemical bonds. It is a powerful tool in organic synthesis, particularly in the context of olefin metathesis reactions.

5 Must Know Facts For Your Next Test

1. Metathesis reactions involve the redistribution of chemical fragments, typically through the breaking and formation of carbon-carbon double bonds.
2. Olefin metathesis is a widely used metathesis reaction in organic synthesis, allowing for the formation of new carbon-carbon double bonds.
3. Intramolecular olefin metathesis, such as ring-closing metathesis (RCM), is a powerful tool for the synthesis of cyclic organic compounds.
4. Grubbs catalysts are a class of highly efficient and versatile catalysts that enable a wide range of olefin metathesis reactions, including RCM.
5. Metathesis reactions are often used in the synthesis of complex natural products and pharmaceuticals, as well as in the preparation of polymeric materials.

Review Questions

• Explain the general mechanism of an olefin metathesis reaction and how it differs from other types of organic reactions.
  • In an olefin metathesis reaction, two alkene (olefin) molecules exchange their substituents, leading to the formation of new alkene products. This process involves the breaking and reforming of carbon-carbon double bonds, which is facilitated by a metal-based catalyst, such as a Grubbs catalyst. The metathesis mechanism is distinct from other organic reactions, as it does not involve the addition or removal of functional groups, but rather the rearrangement of existing bonds.
• Describe the key features and applications of intramolecular olefin metathesis, particularly in the context of ring-closing metathesis (RCM).
  • Intramolecular olefin metathesis, such as ring-closing metathesis (RCM), is a powerful synthetic tool for the construction of cyclic organic compounds. In RCM, two alkene groups within the same molecule are brought together by the metathesis catalyst, resulting in the formation of a cyclic alkene product. This process is highly useful for the synthesis of medium-sized and large-sized rings, which can be challenging to achieve through other methods. RCM has found widespread applications in the synthesis of natural products, pharmaceuticals, and other complex organic molecules.
• Evaluate the role of Grubbs catalysts in enabling a wide range of olefin metathesis reactions, and discuss the factors that contribute to their efficiency and versatility.
  • Grubbs catalysts are a class of ruthenium-based organometallic complexes that have revolutionized the field of olefin metathesis. These catalysts are highly efficient, tolerant of a wide range of functional groups, and can be tuned to perform various types of metathesis reactions, including ring-closing, cross-metathesis, and ring-opening metathesis polymerization. The versatility of Grubbs catalysts is attributed to their unique electronic and steric properties, which allow for the selective activation and coordination of the olefin substrates. Additionally, the development of different generations of Grubbs catalysts, with improved catalytic activity and functional group tolerance, has further expanded the synthetic utility of olefin metathesis in organic chemistry.

Related terms

Olefin Metathesis: A type of metathesis reaction involving the exchange of alkene (olefin) fragments between two molecules, leading to the formation of new alkene products.

Grubbs Catalyst: A class of ruthenium-based organometallic complexes that act as efficient catalysts for olefin metathesis reactions.

Ring-Closing Metathesis (RCM): A type of intramolecular olefin metathesis reaction that forms cyclic alkene products from acyclic precursors.