Wacker oxidation template

Wacker process cycle: hydroxypalladation of ethene by Pd(II) and water, β-hydride elimination and re-insertion giving acetaldehyde and H–Pd–Cl, loss of HCl to Pd(0), and reoxidation by CuCl₂ (CuCl + O₂ regenerate it); key step: water attacks the Pd-bound alkene.

What the template shows

• PdCl₂ turns ethene and water into acetaldehyde; CuCl₂ and O₂ reoxidise the palladium
• Overall: CH₂=CH₂ + ½ O₂ → CH₃CHO (cat. PdCl₂, cat. CuCl₂, H₂O, HCl)
• PdCl₂ (as PdCl₄²⁻)
• The carbonyl oxygen comes from water, not from O₂; O₂ only reoxidises copper.
• Pd(II) is the oxidant and is reduced to Pd(0); CuCl₂ turns it back into Pd(II), and O₂ regenerates CuCl₂.
• Ligands and charges on Pd (PdCl₄²⁻, aqua and alkene ligands) are simplified here.
• With terminal alkenes RCH=CH₂ (Tsuji–Wacker) the product is the methyl ketone RCOCH₃ (Markovnikov).
• Key step: water attacks the coordinated alkene
• Pd(II) pulls electron density from ethene, so water adds to carbon (from the face away from Pd, anti) and the C=C π electrons form the C–Pd bond; the oxonium ion then loses H⁺.
• Chloride and water ligands on Pd are simplified · every part of this figure is editable

Drawn with 24 atoms, 7 arrows, 99 shapes – every one editable in MolDraw.

Sources

• Smidt, Hafner, Jira, Sedlmeier, Sieber, Rüttinger & Kojer, Angew. Chem. 1959, 71, 176 Original paper
• Crabtree, The Organometallic Chemistry of the Transition Metals, 6th ed., Wiley 2014 Textbook