Catalytic transfer hydrogenation (Midterm)

Catalytic transfer hydrogenation is used in processing of __ __.

Vegetable oils

Saturated fats do not contain __. They are __ at room temp.

Alkenes. Solid.

Vegetable oils contain __. They are typically __ at room temp, but can be made into __ by hydrogenation.

Alkenes. Liquids but can be made into solids.

Hydrogenation of an alkene pi bond

Reduction reaction. Increases hydrogen content, and changes physical and chemical properties.

Closing the loop

Using outputs of one process as inputs for another process, decreasing environmental impact of waste streams

Day 1 techniques of transfer hydrogenation

1. heating at reflux

2. filtration

3. ‘workup’ on aqueous organic extraction

4. rotovap

Day 2 techniques for purification and characterization

1. recrystallization

2. purity: IR and melting point

3. identity: IR and melting point

Reduction at a carbon atom identified by…

Decreased number of bonds to electronegative atoms, increased hydrogen content

Purpose of rotovap

Separate solvent from the organic compound. Heat can boil off the solvent, lower pressure will not damage the organic solid. Rotation increases surface area for faster evaporation

Purpose of recrystallization, through vacuum filtration

Is a purification process in which the desired products forms crystals from solutions

What is the purpose of the wetted filter paper during vacuum filtration?

The wetted paper (with the solvent with the organic compound) get vacuumed over the funnels holes to provide a barrier to prevent the solid from draining into the flask with the solvent

Purpose of separation from extraction with separatory funnel

Allows separation of immiscible liquids (aqueous layer and organic layers)

Overlap of two hydrogens s-orbitals of opposite signs give __ __.

Destructive interference = a node between the atoms = antibonding

Overlap of two hydrogens s-orbitals of same signs give __ __.

Constructive interference = bonding

LUMO

Lowest Unoccupied Molecular Orbital. Usually antibonding

HOMO

Highest Occupied Molecular Orbital. Usually bonding

Alkene pi bonds are reduced by __ __.

Catalytic hydrogenation

Catalyst purpose

Lowers energetic barriers (activation energy), but it is not consumed in the reaction

Homogeneous catalysis

Presence of Ni, Pd, or Pt in solution as catalyst

Catalyst we used in experiment

Heterogeneous catalysis, specifically the solid Pd cat.

Using the solid Pd catalyst allowed for the reactions steps to occur on __ __ __.

the surface of the metal

Where does the Pd catalyst obtain the H’s from?

From formate ions

Advantages of heterogeneous catalyst over homogeneous catalysis

A solid catalyst in heterogeneous catalysis can be reused/recycled, rather than dissolving in the organic solvents

When H₂ adds across an alkene they are added by __ addition.

Syn addition

Enantioselective catalysis is if the product is __ and a reaction occurs in a __ environment, one enantiomer may be produced in greater quantity.

Chiral in a chiral environment

Our reaction __ occur in a chiral environment. The __ addition can occur on either face of the alkene = __ product.

Doesn’t. Syn addition. Racemic.

Purpose of heating at reflux

The reaction proceeds to an elevated, controlled temperature without losing solvent/reactants due to evaporation by continuous condensing and return of vapors