3. A Wilkinsons catalyst is widely used in the hydrogenation of alkenes. Show a catalytic cycle, including: i. chemical structure of the catalyst, with complete stereochemistry ii. molecular geometry of catalyst iii. type of reactions involved iv. the appropriate starting material, reagent and solvent v. major and minor end-products vi. all intermediates, for each reaction stated in (iii)

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karelle42 · Accepted Answer

We can see here that the catalytic cycle for the hydrogenation of alkenes using Wilkinson's catalyst involves several steps.

What are the steps involved?

Here's an overview of the catalytic cycle, including the necessary details:

i. Chemical structure of the catalyst:

Wilkinson's catalyst, also known as chloridotris(triphenylphosphine)rhodium(I), has the following chemical structure: [RhCl(PPh3)3]

ii. Molecular geometry of the catalyst:

The Wilkinson's catalyst has a trigonal bipyramidal geometry around the rhodium center. The three triphenylphosphine (PPh3) ligands occupy equatorial positions, while the chloride (Cl) ligand occupies an axial position.

iii. Type of reactions involved:

The catalytic cycle involves several reactions, including:

Oxidative addition: The rhodium center undergoes oxidative addition, reacting with molecular hydrogen (H2) to form a dihydride intermediate.Alkene coordination: The alkene substrate coordinates to the rhodium center, forming a π-complex.Hydrogenation: The coordinated alkene undergoes hydrogenation, resulting in the addition of hydrogen atoms to the double bond and formation of a metal-alkyl intermediate.Reoxidation: The metal-alkyl intermediate reacts with a hydrogen molecule to regenerate the rhodium dihydride species.

iv. Starting material, reagent, and solvent:

The starting material is an alkene, and the reagent is Wilkinson's catalyst ([RhCl(PPh3)3]). The reaction is typically carried out in a suitable solvent, such as dichloromethane (CH2Cl2) or tetrahydrofuran (THF).

v. Major and minor end-products:

The major end-product of the hydrogenation reaction is the fully saturated alkane, resulting from the addition of hydrogen across the double bond. The minor end-product may include cis- or trans-configured alkanes if the original alkene substrate possesses geometric isomers.

vi. Intermediates:

The intermediates in the catalytic cycle include:

Rhodium dihydride complex: [RhH2(PPh3)3]Alkene-Rhodium π-complex: [Rh(η2-alkene)(PPh3)3]Metal-alkyl intermediate: [Rh(alkyl)(PPh3)3]

These intermediates play a crucial role in facilitating the hydrogenation reaction and enabling the catalytic cycle to proceed.

Learn more about Wilkinson’s catalyst on https://brainly.com/question/31972308

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