--- title: "Identify the unknown: C₄H₈O Template | MolDraw" url: https://www.moldraw.com/templates/spectro-identify-unknown/ description: "Identify the unknown: C₄H₈O template: Combined spectroscopy problem: C₄H₈O (degree of unsaturation 1), IR C=O 1715 cm⁻¹ and no O–H, ¹H NMR δ 2.44 (q, 2H)…" lang: en publisher: Scidart Academy generated: 2026-10-28 --- [MolDraw](https://www.moldraw.com/) › [Templates](https://www.moldraw.com/templates/) › [Spectroscopy](https://www.moldraw.com/templates/spectroscopy/) › Identify the unknown: C₄H₈O [Spectroscopy](https://www.moldraw.com/templates/spectroscopy/)Premium # Identify the unknown: C₄H₈O template ![Identify the unknown: C₄H₈O template: Combined spectroscopy problem: C₄H₈O (degree of unsaturation 1), IR C=O 1715 cm⁻¹ and no O–H, ¹H NMR δ 2.44 (q, 2H), 2.14 (s, 3H), 1.06 (t, 3H) → butan-2-one, with each reasoning step.](https://www.moldraw.com/templates/spectro-identify-unknown.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). Combined spectroscopy problem: C₄H₈O (degree of unsaturation 1), IR C=O 1715 cm⁻¹ and no O–H, ¹H NMR δ 2.44 (q, 2H), 2.14 (s, 3H), 1.06 (t, 3H) → butan-2-one, with each reasoning step. ## What the template shows - Worked problem: molecular formula → degree of unsaturation → IR → ¹H NMR → structure - Problem and solution - Molecular formula C₄H₈O (from M⁺• = 72 and combustion analysis) - Degree of unsaturation = (2C + 2 + N − H − X) / 2 = (2×4 + 2 − 8) / 2 = 1 → one ring or one π bond (C=O or C=C). - Strong band at 1715 cm⁻¹: C=O (the one degree of unsaturation). No broad O–H (3200–3550), no aldehyde C–H (2720). → a ketone. - ¹H NMR spectrum (CDCl₃, typical values) - δ / ppm (chemical shift; downfield ← → upfield) - Nothing above δ 5 (no CHO, Ar–H or CO₂H), so only δ 5–0 is shown. Three environments, integrals 2 : 3 : 3 = 8 H. q (2H) + t (3H), same J → CH₃CH₂–. s (3H) at δ 2.1 → CH₃–C=O. CH₂ at δ 2.4: next to C=O. - Put the pieces together: CH₃–C(=O)–CH₂CH₃ - Butan-2-one (methyl ethyl ketone), C₄H₈O, M = 72. Fits: DoU 1 (C=O), IR 1715 cm⁻¹, three ¹H signals 2H q / 3H s / 3H t. - Always start from the formula: the degree of unsaturation limits the options (1 = one ring or one π bond). - IR picks the functional group: strong 1715 cm⁻¹ = C=O; no broad O–H, no aldehyde C–H at 2720 → ketone. - NMR integrals must add up to the H count of the formula (2 + 3 + 3 = 8). - Quartet (2H) + triplet (3H) = CH₃CH₂–; a singlet CH₃ near δ 2.1 = CH₃C=O. - Check the answer against every piece of data, and rule out isomers: butanal would show CHO at δ 9.8; but-3-en-2-ol would show O–H and C=C. - Practise with real spectra in the free MolDraw NMR and IR viewers. - Typical literature values; compare real spectra in SDBS · every part of this figure is editable Drawn with 5 atoms, 189 shapes – every one editable in MolDraw. ## Sources - [Pavia, Lampman, Kriz & Vyvyan, Introduction to Spectroscopy, 5th ed., Cengage 2015, ch. 1–3](https://openlibrary.org/isbn/9781285460123) Textbook - [Silverstein, Webster, Kiemle & Bryce, Spectrometric Identification of Organic Compounds, 8th ed., Wiley 2014](https://openlibrary.org/isbn/9780470616376) Textbook - [SDBS Spectral Database for Organic Compounds (AIST)](https://sdbs.db.aist.go.jp/) Database ## 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 Identify the unknown: C₄H₈O template free? You can preview the Identify the unknown: C₄H₈O 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 Identify the unknown: C₄H₈O 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 spectra real data? 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