Question

Wacker oxidation of alkenes is catalyzed by a combination of

• A. Pd(II) and Cu(II)
• B. Co(II) and Cu(II)
• C. Pd(II) and Ni(II)
• D. Pd(II) and Co(II)

Hint:

The Wacker process is widely used in industry to manufacture acetaldehyde from ethylene.
Always remember: Pd(II) is the main catalyst, while Cu(II) is a co-catalyst to regenerate Pd(II) from Pd(0).
Oxidizing conditions are maintained using molecular oxygen in the reaction medium.

Answer 1

The Correct Option is A

Step 1: The Wacker oxidation is an industrially important reaction that converts alkenes (like ethylene) into aldehydes or ketones by oxidation. For example, ethylene gets oxidized to acetaldehyde.
Step 2: The reaction proceeds with the help of a palladium catalyst. Pd(II) species first coordinates to the alkene and facilitates the insertion of water, forming an alcohol group.
Step 3: During the process, Pd(II) gets reduced to Pd(0). To regenerate Pd(II) from Pd(0), a co-catalyst is needed. This role is played by Cu(II), which oxidizes Pd(0) back to Pd(II).
Step 4: Thus, the overall catalytic system requires both Pd(II) and Cu(II). Without Cu(II), the cycle would stop because Pd(0) would accumulate and the oxidation would not proceed efficiently.
\[ \ce{CH2=CH2 + 1/2 O2 + H2O →[PdCl2/CuCl2] CH3CHO} \]
Hence, the correct catalytic combination is Pd(II) and Cu(II).