--- title: "Hydration of an alkyne Template – Chemistry Diagram | MolDraw" url: https://www.moldraw.com/templates/alkyne-hydration/ description: "Hydration of an alkyne template: Propyne with HgSO₄ in aqueous H₂SO₄: Hg²⁺ activates the triple bond, water adds to the inner carbon, H⁺ replaces Hg²⁺ and…" lang: en publisher: Scidart Academy generated: 2026-11-13 --- [MolDraw](https://www.moldraw.com/) › [Templates](https://www.moldraw.com/templates/) › [Mechanisms](https://www.moldraw.com/templates/mechanisms/) › Hydration of an alkyne [Mechanisms](https://www.moldraw.com/templates/mechanisms/)Premium # Hydration of an alkyne template ![Hydration of an alkyne template: Propyne with HgSO₄ in aqueous H₂SO₄: Hg²⁺ activates the triple bond, water adds to the inner carbon, H⁺ replaces Hg²⁺ and the enol tautomerises to propanone.](https://www.moldraw.com/templates/alkyne-hydration.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). Propyne with HgSO₄ in aqueous H₂SO₄: Hg²⁺ activates the triple bond, water adds to the inner carbon, H⁺ replaces Hg²⁺ and the enol tautomerises to propanone. ## Mechanism step by step Hg²⁺ and H₂SO₄ add water Markovnikov; the enol formed tautomerises to a ketone 1. **Hg²⁺ adds** – The π bond attacks Hg²⁺ (drawn open; really a bridged π complex) 2. **Water adds** – At the more substituted carbon (Markovnikov) 3. **Deprotonation** – A mercury-substituted enol 4. **C-Protonation** – H⁺ adds to the carbon carrying Hg 5. **Loss of Hg²⁺** – The catalyst leaves: the neutral enol 6. **Tautomerism 1** – The enol C=C takes H⁺ 7. **Tautomerism 2** – Loss of H⁺ from O: the ketone ## Key points - Markovnikov: terminal alkynes give methyl ketones; only ethyne gives an aldehyde (ethanal). - The enol is not isolated: the keto form is far more stable. - Hg²⁺ is regenerated, so it is a catalyst. - Hydroboration–oxidation of a terminal alkyne with a bulky borane (disiamylborane or 9-BBN) gives the aldehyde instead (anti-Markovnikov). Drawn with 87 atoms, 23 arrows, 9 shapes – every one editable in MolDraw. ## Sources - [Clayden, Greeves & Warren, Organic Chemistry, 2nd ed., OUP 2012, ch. 19](https://openlibrary.org/isbn/9780199270293) Textbook - [Smith, March's Advanced Organic Chemistry, 8th ed., Wiley 2020, ch. 15](https://openlibrary.org/isbn/9781119371809) 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 Hydration of an alkyne template free? You can preview the Hydration of an alkyne 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 Hydration of an alkyne 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. ### What is a curly-arrow mechanism template? A ready-made drawing of a reaction mechanism in which curved arrows show where electron pairs move in each step. 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