1. Elmhurst College, Elmhurst, Illinois
Wacker Process
Jacob McNamara
Elmhurst College, Elmhurst, Illinois
Problems with the old synthesis:
-Originally produced for acetaldehyde
-this was expensive due to the high
temp. combustions of light hydrocarbons
-28 cents per pound was the cost
Solution to this problem:
-Started with ethylene, which only costs 3.5 cents per pound
Step 1 +
PdCl4 reacts with ethylene to form PdCl3 with a bond connecting to the bond of H2C=CH2
Old Initial Synthesis of Olefins
Used mainly in the oil industry
Step 2 +
Detailed Mechanism for Step 4
This palladium complex reacts with water to eject a chlorine atom
New Synthesis of Olefins:
Replace a hydrogen on the ethylene molecule with
the desired ligand by a basic substitution reaction.
Step 3 +
Based on the HOMO diagram below, another molecule of water attacks the pi-bond
on the ethylene portion of the molecule, causing a CH2CH2OH chain to form.
The palladium catalyst is regenerated
by a reaction with CuCl2
Detailed
Mechanism
Step 4
Refer to the mechanism to the right for how this reaction takes place
Metal-olefin complexes use back-bonding
- this means there is a decrease in electron density
of the pi-bonding orbital of the olefin and a gain
of electron density in the pi-star orbital.
Step 5
A molecule of water comes, and its lone pair takes the hydrogen atom off of the oxygen,
which gives the final product, plus some hydronium ions.