Identify the Unknown Compound
A-Level Chemistry Spectroscopy Challenge
One of the most enjoyable topics in A-Level Chemistry is figuring out what on earth a compound actually is using nothing more than its spectra. No labels. No names. Just clues.
Today’s challenge is a classic OCR-style spectroscopy problem, using four powerful techniques:
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Mass spectrometry
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Infra-red (IR) spectroscopy
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Proton (¹H) NMR
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Carbon-13 (¹³C) NMR
Below is a set of spectra for an unknown organic compound. Your task is to identify the substance.
📘 The Question (OCR Style)
An unknown organic compound has the following spectroscopic data:
Mass spectrum
Molecular ion peak at m/z = 89 (very small)
Fragment peaks at m/z = 74, 44, and 43
Infra-red (IR) spectrum
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Broad absorption between 2500–3300 cm⁻¹
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Strong absorption at approximately 1700 cm⁻¹
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Absorption near 1550 cm⁻¹
¹H NMR spectrum
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Signal at ≈ 1.5 ppm, integrating to 3 protons
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Signal at ≈ 3.8 ppm, integrating to 1 proton
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Broad signal at ≈ 8–10 ppm
¹³C NMR spectrum
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Three carbon environments
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One signal at ≈ 175 ppm
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One signal at ≈ 50 ppm
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One signal at ≈ 20 ppm
❓ Your Task
Using all of the spectroscopic evidence, identify the compound.
No Googling. No AI, No peeking.
Think structure first, not just formula.
Answer revealed tomorrow, with a full step-by-step breakdown showing how each spectrum contributes to the final identification.
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