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Étard reaction template
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Toluene and chromyl chloride in CS₂ give a brown solid, the Étard complex, with two CrO₂Cl₂ units on the methyl carbon. Hydrolysis releases benzaldehyde without further oxidation to the acid.
Mechanism step by step
Chromyl chloride oxidises toluene to benzaldehyde and stops there
- Ene-type C–H addition (proposed) – A Cr=O oxygen takes a benzylic H while the carbon bonds to chromium
- Étard complex – Rearrangement to C–O–Cr and a second CrO₂Cl₂ give the brown complex, which precipitates from CS₂
- Hydrolysis – Water breaks the complex: benzaldehyde
Key points
- The aldehyde is protected in the complex, so it is not oxidised on to benzoic acid.
- Compare: KMnO₄ or K₂Cr₂O₇ oxidise the side chain all the way to benzoic acid.
- Another route to benzaldehyde from toluene: CrO₃ in acetic anhydride gives the benzylidene diacetate, which is then hydrolysed.
- The complex is usually written C₆H₅CH(OCrOHCl₂)₂; its exact mechanism is still debated (an ene step and a [2,3] shift are proposed).
Drawn with 94 atoms, 6 arrows, 7 shapes – every one editable in MolDraw.
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Frequently asked questions
Is the Étard reaction template free?
You can preview the Étard reaction template here and open and edit it in MolDraw for free. Downloading or exporting it is part of MolDraw Pro, together with the other premium templates.
Can I edit the Étard reaction template?
Yes. It opens as an ordinary MolDraw drawing, so every structure, arrow, label and colour can be changed, and you can add your own content around it.
Is the chemistry checked?
Every structure is checked with RDKit and every curly arrow passes MolDraw’s electron-flow audit. The sources used are listed on this page.
Which name reactions are included?
Over seventy, covering the reactions most often asked in school-leaving exams (A-level, IB, CBSE, JEE and NEET) and first-year university courses, including condensations, rearrangements, oxidations, reductions and aromatic substitutions.