Metathesis Reactions in Organic Chemistry

The video tutorial introduces metathesis reactions, focusing on sigma-sigma, sigma-pi, and pi-pi metathesis. It explains the concerted nature of these reactions, where bonds break and form simultaneously. The tutorial provides examples using metals like zirconium, hafnium, and scandium, highlighting the importance of d0 metals and the role of hydrogen. It also discusses the reversibility of pi-pi metathesis and its potential applications in ligand modification.

What is the primary characteristic of metathesis reactions?

• They only involve sigma bonds.

• They involve the breaking and forming of bonds in a concerted manner.

• They require the presence of a catalyst.

• They are irreversible reactions.

In sigma-sigma metathesis, what is essential for the metal involved?

• It should be a transition metal.

• It must be d0, with no d valence electrons.

• It should be in a high oxidation state.

• It must have d10 configuration.

What is a key difference between sigma-sigma and sigma-pi metathesis?

• Sigma-sigma involves only pi bonds.

• Sigma-pi requires a catalyst.

• Sigma-pi results in one molecular entity as the product.

• Sigma-sigma is irreversible.

In sigma-pi metathesis, what type of bonds are broken and formed?

• Two sigma bonds are broken and two pi bonds are formed.

• Two pi bonds are broken and two sigma bonds are formed.

• Only pi bonds are involved.

• One sigma and one pi bond are broken, forming two new sigma bonds.

What is unique about pi-pi metathesis compared to other types?

• It is not reversible.

• It requires a catalyst.

• It only involves triple bonds.

• The metal does not need to be d0.

Which type of metathesis can involve triple bonds?

• Sigma-pi metathesis

• Pi-pi metathesis

• None of the above

• Sigma-sigma metathesis

In the example of sigma-sigma metathesis with hafnium, what is the product?

• Ethene and a hydride ligand

• Ethene and an alkyl ligand

• Methane and a hydride ligand

• Methane and an alkyl ligand

What happens to the ligand in sigma-pi metathesis with scandium and ethene?

• It shortens by two carbons.

• It lengthens by two carbons.

• It remains unchanged.

• It forms a new double bond.

How can pi-pi metathesis be reversed?

• By adding more reactants.

• By heating the reaction.

• By breaking the four-membered ring into two double bonds.

• By adding a catalyst.

What is the final product in the pi-pi metathesis example with titanium?

• A single alkyl ligand.

• A four-membered ring with a phenyl group on the same carbon.

• A four-membered ring with a phenyl group on a different carbon.

• Two separate molecular entities.