--- title: "Osazone formation Template – Chemistry Diagram | MolDraw" url: https://www.moldraw.com/templates/sugar-osazone-formation/ description: "Osazone formation template: D-Glucose forms a phenylhydrazone at C1, which tautomerises to the ene-hydrazine; protonation and loss of aniline oxidise C2 to a…" lang: en publisher: Scidart Academy generated: 2026-11-13 --- [MolDraw](https://www.moldraw.com/) › [Templates](https://www.moldraw.com/templates/) › [Biochemistry](https://www.moldraw.com/templates/biochemistry/) › Osazone formation [Biochemistry](https://www.moldraw.com/templates/biochemistry/)Premium # Osazone formation template ![Osazone formation template: D-Glucose forms a phenylhydrazone at C1, which tautomerises to the ene-hydrazine; protonation and loss of aniline oxidise C2 to a keto-imine, and two more phenylhydrazine molecules convert it into D-glucosazone with loss of ammonia and water.](https://www.moldraw.com/templates/sugar-osazone-formation.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). D-Glucose forms a phenylhydrazone at C1, which tautomerises to the ene-hydrazine; protonation and loss of aniline oxidise C2 to a keto-imine, and two more phenylhydrazine molecules convert it into D-glucosazone with loss of ammonia and water. ## Mechanism step by step Three PhNHNH₂ turn C1 and C2 of a sugar into a bis(phenylhydrazone): glucose, mannose and fructose give the same osazone 1. **Phenylhydrazone** – PhNHNH₂ condenses with the C1 aldehyde (summarised); R = C3–C6 chain, unchanged 2. **Tautomerisation** – H moves from C2 to N: the ene-hydrazine (enol) form (summarised) 3. **Protonation** – Acid protonates the NHPh nitrogen 4. **Loss of aniline** – The enol O pushes electrons along C=C and N–N breaks: C2 is oxidised, C1 becomes an imine 5. **Deprotonation** – The keto-imine 6. **Two more PhNHNH₂** – C2=O gives a hydrazone and C1=NH exchanges NH₃ for NNHPh: the osazone (summarised) ## Key points - Only C1 and C2 react, so D-glucose, D-mannose (its C2 epimer) and D-fructose (the 2-ketose) give the same osazone: proof that they share the C3–C5 configuration. - Stoichiometry: sugar + 3 PhNHNH₂ → osazone + PhNH₂ + NH₃ + 2 H₂O; one PhNHNH₂ is the oxidant, ending up as aniline and ammonia. - The reaction stops at C2 because the osazone is stabilised by an intramolecular N–H···N hydrogen-bonded chelate ring. - Osazones are yellow crystalline solids with characteristic crystal shapes and formation times, once used to identify sugars. Drawn with 194 atoms, 14 arrows, 12 shapes – every one editable in MolDraw. ## Sources - [Furniss et al., Vogel's Textbook of Practical Organic Chemistry, 5th ed., Longman 1989, ch. 9](https://openlibrary.org/isbn/9780582462366) 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 Osazone formation template free? You can preview the Osazone formation 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 Osazone formation 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. ### Are the biochemical pathways drawn with structures? Yes. 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