PHD
  1. Inorganic chemistry  1.1. Coordination chemistry  1.1.1. Ligand field theory  1.1.2. Crystal field theory  1.1.3. Molecular Orbital Theory for Coordination Compounds  1.1.4. Stability of Coordination Compounds  1.1.5. Electronic spectra of coordination compounds  1.1.6. Isomerism in Coordination Compounds  1.1.7. Kinetics and mechanism of coordination reactions  1.2. Organometallic Chemistry  1.2.1. Metal Carbonyls  1.2.2. Metal alkyl and aryl  1.2.3. Fischer and Schrock carbonaceans  1.2.4. Oxidative Addition and Reductive Elimination  1.2.5. Metal Hydrides  1.2.6. Catalysis by organometallic compounds  1.2.7. Metallocenes and Sandwich Complexes  1.2.8. CH activation  1.3. Solid state chemistry  1.3.1. Crystal structures and lattices  1.3.2. Band theory and electrical properties  1.3.3. Defects in the crystal  1.3.4. Synthesis of solid state materials  1.3.5. Magnetic and optical properties of solids  1.3.6. Superconductivity  1.3.7. Solid state ionics  1.4. Bio-inorganic chemistry  1.4.1. Metalloproteins and enzymes  1.4.2. Metal ion transport and storage  1.4.3. The role of metals in medicine  1.4.4. Bioinspired catalysis  1.4.5. Metal–DNA interactions  1.4.6. Metal Complexes in Medical Science  1.5. Lanthanides and Actinides  1.5.1. Electronic configuration and oxidation states in lanthanides and actinides  1.5.2. Spectral and Magnetic Properties in Lanthanides and Actinides  1.5.3. Separation and Extraction of Lanthanides and Actinides  1.5.4. Coordination chemistry of f-block elements  1.6. Main Group Chemistry  1.6.1. Chemistry of boron compounds  1.6.2. Chemistry of Silicon and Germanium Compounds  1.6.3. Chemistry of Phosphorus and Sulfur Compounds  1.6.4. Organosilicon chemistry  1.6.5. Noble Gas Chemistry
  2. Organic chemistry  2.1. Reaction mechanism  2.1.1. Nucleophilic substitution reactions  2.1.2. Electrophilic addition and substitution reactions  2.1.3. Elimination reactions  2.1.4. Rearrangement reactions  2.1.5. Radical reactions  2.1.6. Pericyclic Reactions  2.1.7. Photochemical reactions  2.2. Stereoscopic  2.2.1. Chirality and optical activity  2.2.2. Structural analysis  2.2.3. Stereoelectronic effects  2.2.4. Asymmetric synthesis  2.2.5. Dynamic Stereochemistry  2.3. Organometallic Chemistry in Organic Synthesis  2.3.1. Organolithium and organomagnesium reagents  2.3.2. Transition metal catalyzed coupling reactions  2.3.3. Palladium-catalyzed reactions  2.3.4. Olefin Metathesis  2.3.5. Gold and silver catalysis  2.4. Natural products chemistry  2.4.1. Alkaloids and terpenoids  2.4.2. Steroids and Flavonoids  2.4.3. Total synthesis of natural products  2.4.4. Biosynthesis of natural products  2.5. Supramolecular Chemistry  2.5.1. Host-Guest Chemistry  2.5.2. Self-assembly and molecular recognition  2.5.3. Supramolecular Catalysis  2.5.4. Molecular Machines
  3. Physical Chemistry  3.1. Thermodynamics  3.1.1. Laws of Thermodynamics  3.1.2. Chemical Potential and Equilibrium  3.1.3. Statistical thermodynamics  3.1.4. Non-equilibrium thermodynamics  3.2. Quantum Chemistry  3.2.1. Schrödinger equation and its applications  3.2.2. Molecular orbital theory  3.2.3. Density functional theory  3.2.4. Post-Hartree–Fock methods  3.3. Chemical kinetics  3.3.1. Reaction rate theory  3.3.2. Mechanism and rate laws  3.3.3. Catalysis and enzyme kinetics  3.3.4. Reaction dynamics  3.4. Spectroscopy and molecular structure  3.4.1. Infrared Spectroscopy  3.4.2. UV-visible spectroscopy  3.4.3. Nuclear Magnetic Resonance Spectroscopy  3.4.4. Mass Spectrometry  3.4.5. Raman Spectroscopy  3.5. Surface and Colloid Chemistry  3.5.1. Absorption and Catalysis  3.5.2. Surfactants and micelles  3.5.3. Colloidal Stability  3.5.4. Nanomaterials and Interfaces
  4. Analytical chemistry  4.1. Chromatography  4.1.1. Gas Chromatography  4.1.2. High Performance Liquid Chromatography  4.1.3. Thin Layer Chromatography  4.1.4. Ion Chromatography  4.2. Electroanalytical techniques  4.2.1. Voltammetry and Polarography  4.2.2. Conductometry and potentiometry  4.2.3. Colometry  4.3. Spectroscopic Methods  4.3.1. Atomic absorption spectroscopy  4.3.2. Fluorescence Spectroscopy  4.3.3. X-ray diffraction  4.3.4. Electron paramagnetic resonance spectroscopy  4.4. Chemometrics  4.4.1. Data processing and statistical methods  4.4.2. Multidisciplinary analysis  4.4.3. Machine Learning in Analytical Chemistry
  5. Theoretical and Computational Chemistry  5.1. Molecular dynamics simulation  5.2. Quantum chemistry methods  5.3. Computational drug design  5.4. Machine Learning in Chemistry  5.5. Ab initio molecular dynamics
  6. Biophysics and Medicinal Chemistry  6.1. Drug discovery and design  6.2. Enzyme kinetics and inhibition  6.3. Chemical biology approach  6.4. Protein-ligand interactions  6.5. Bioorthogonal chemistry
  7. Materials chemistry  7.1. Polymer chemistry  7.1.1. Polymerization mechanism  7.1.2. Functional Polymers  7.1.3. Biodegradable Polymer  7.1.4. Conducting and semiconducting polymers  7.2. Nano Chemistry  7.2.1. Nanoparticles and nanostructures  7.2.2. Carbon-based nanomaterials  7.2.3. Quantum dots  7.3. Energy and Environmental Chemistry  7.3.1. Battery and Fuel Cell Chemistry  7.3.2. Green chemistry and sustainable materials  7.3.3. Photocatalysis

PHD → Organic chemistry → Organometallic Chemistry in Organic Synthesis ↓


Olefin Metathesis


Olefin metathesis is a widely used and versatile reaction in the field of organometallic chemistry and organic synthesis. It involves the redistribution of alkene fragments by fragmentation and regeneration of carbon-carbon double bonds. This reaction is of great importance in both academia and industry for the synthesis of complex molecules.

Basic concept

In olefin metathesis, two alkenes are brought together, and their backbone carbon-carbon double bonds are exchanged, forming new olefins. The basic idea is that olefins, which are hydrocarbons with carbon-carbon double bonds, are broken down and then re-formed to yield different olefinic products.

The general reaction can be depicted in the following outline:

        R 1 CH=CHR 2 + R 3 CH=CHR 4 ↔ R 1 CH=CHR 3 + R 2 CH=CHR 4

Historical background

Olefin metathesis was first observed in the mid-20th century. The term "metathesis" was coined by Calderon and others in 1967. There were no significant breakthroughs in the field of olefin metathesis until the development of well-defined metal-carbene complexes by researchers such as Chauvin, Schrock and Grubbs. These researchers were awarded the Nobel Prize in Chemistry in 2005 for the development of the metathesis method in organic synthesis.

Types of olefin metathesis reactions

There are several types of olefin metathesis reactions, each with its own specific properties and applications:

1. Cross metathesis (CM)

In cross metathesis the reaction of two different olefins leads to the formation of two different olefinic products. The selectivity and yield of cross metathesis depend strongly on the structure and reactivity of the starting materials.

        R 2 C=CHR + R'CH=CR' → R 2 C=CR' + R'CH=CHR

2. Ring-closing metathesis (RCM)

Ring-closing metathesis is a reaction that results in the formation of ring structures by joining the ends of a diene. RCM is highly useful in the synthesis of cyclic compounds, especially in the synthesis of medium and large rings.

        RN=CHCH=CHR' → R-CH=CHR'
An illustration of ring-closing metathesis, where a diene forms a ring structure. Diane Cyclic compounds

3. Ring-opening metathesis (ROM)

Ring-opening metathesis involves the fragmentation of a cyclic olefin to yield a diene. Used in polymer synthesis, this reaction exploits strain in cyclic olefins such as norbornene.

        cycloalkene → open chain diene

4. Ring-opening metathesis polymerization (ROMP)

ROMP is a powerful method for preparing polymers. In this, polyolefins are formed by polymerization of cyclic olefins in the presence of a catalyst.

        n(Cycloalkene) → polymer
Representation of a polymer chain formed via ring-opening metathesis polymerization.

Catalyst in olefin metathesis

The efficiency and practicality of olefin metathesis depends largely on the catalysts used. The most successful catalysts are metal alkylidenes, with significant contributions from molybdenum (Mo), tungsten (W), and ruthenium (Ru)-based complexes.

Schrock catalyst

Schrock catalysts contain molybdenum or tungsten, which are highly active but sensitive to air and moisture.

General structure:

        M(alkylidene)(OR) n

Grubbs catalysts

Grubbs catalysts are ruthenium carbenes known for their tolerance to a wide variety of functional groups and environmental conditions. They are among the most widely used and studied catalysts due to their ease of use and robustness.

General structure:

        RS(=CHR)(L) 2 (X) 2
Simplified structure of the Grubbs catalyst. Are you l

Applications of olefin metathesis

The impact of olefin metathesis extends across diverse areas of chemical research and manufacturing. It provides a streamlined and efficient route to synthesize diverse organic compounds, including polymers, natural products, and pharmaceuticals.

1. Polymer synthesis

Using ROMP, a variety of functionalized and nonfunctional polymers are synthesized. This includes materials for coatings, biomedical devices, and elastomers.

2. Synthesis of natural products and pharmaceuticals

The ability of olefin metathesis to form complex molecular structures has been invaluable in the synthesis of bioactive molecules and pharmaceuticals. RCM, in particular, is employed for the synthesis of cyclic peptides and macrocyclic drugs.

3. Materials science

Olefin metathesis is applied in materials science for the development of advanced composite materials, nanostructures, and reactive materials due to its precision and versatility.

Mechanism of olefin metathesis

The mechanism of olefin metathesis involves a series of intermediate steps, facilitated by a catalyst.

Initiation

It begins with the interaction between the catalyst and the olefin, leading to the formation of a metallacyclobutane intermediate.

Publicity

This intermediate undergoes rearrangement, leading to the breakage and reconstruction of the carbon–carbon double bonds of the olefin, a process known as [2+2] cycloaddition and cycloreversion.

Closure

Finally, the reaction ends with the release of the product olefin and the regeneration of the catalyst, which is ready to enter another cycle. The presence of a stable metal-carbene catalyst species ensures the continuity of the metathesis process.

Step-by-step illustration of the olefin metathesis mechanism with catalytic interaction. Are you product

Conclusion

Olefin metathesis is an indispensable tool in contemporary chemical synthesis, making significant contributions to molecular design and materials production. Continued advances in catalyst design and mechanistic understanding will only expand the frontiers of olefin metathesis applications.


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