--- title: "Azo coupling Template – Chemistry Diagram | MolDraw" url: https://www.moldraw.com/templates/azo-coupling/ description: "Azo coupling template: Benzenediazonium attacks phenoxide at the para carbon; loss of the ring proton gives the orange 4-hydroxyazobenzene dye. Preview it…" lang: en publisher: Scidart Academy generated: 2026-10-28 --- [MolDraw](https://www.moldraw.com/) › [Templates](https://www.moldraw.com/templates/) › [Name reactions](https://www.moldraw.com/templates/name-reactions/) › Azo coupling [Name reactions](https://www.moldraw.com/templates/name-reactions/)Premium # Azo coupling template ![Azo coupling template: Benzenediazonium attacks phenoxide at the para carbon; loss of the ring proton gives the orange 4-hydroxyazobenzene dye.](https://www.moldraw.com/templates/azo-coupling.webp) [Edit in MolDraw](https://www.moldraw.com/)Download with Pro Premium template. Preview and edit it free in MolDraw; downloading and exporting it is part of [MolDraw Pro](https://www.moldraw.com/pricing). Benzenediazonium attacks phenoxide at the para carbon; loss of the ring proton gives the orange 4-hydroxyazobenzene dye. ## Mechanism step by step A diazonium ion attacks an activated ring: azo dyes 1. **Electrophilic attack** – Phenoxide attacks through its para carbon 2. **Rearomatisation** – Hydroxide removes the para C–H ## Key points - The diazonium salt is made from aniline with NaNO₂/HCl at 0–5 °C (diazotisation). - A weak electrophile: only phenoxides and anilines react, mainly para. - Phenols couple at pH 9–10; anilines at pH 4–5. - The extended conjugation (Ar–N=N–Ar) absorbs visible light: methyl orange, Sudan dyes. Drawn with 93 atoms, 11 arrows, 6 shapes – every one editable in MolDraw. ## Sources - [Clayden, Greeves & Warren, Organic Chemistry, 2nd ed., OUP 2012](https://openlibrary.org/isbn/9780199270293) Textbook ## How to use this template 1. Press **Edit in MolDraw**. The template opens on the canvas of the free MolDraw editor. 2. Change anything: move structures, edit atoms and labels, recolour highlights or delete what you do not need. 3. Add your own structures, arrows and text next to it, or combine several templates on one page. 4. Export the drawing as PNG, SVG or PDF for slides, worksheets, theses and papers. ## Frequently asked questions ### Is the Azo coupling template free? You can preview the Azo coupling 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 Azo coupling 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? 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