// CHEMISTRY L5 — SPECTROSCOPY

Chemists identify an unknown compound without ever seeing it — by the way it breaks apart, absorbs infrared light, and lines up its hydrogens. Pick a molecule and compare its three spectra side by side.

// FIG. 01 — THE SPECTROMETER BENCH

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// THREE TECHNIQUES, THREE QUESTIONS

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// THE FINGERPRINT REGION

In an infrared spectrum, the region below about 1500 cm⁻¹ is called the fingerprint region. It's a dense, messy set of dips that is unique to each compound — like a barcode. You don't try to assign every peak; instead you match the whole pattern against a database. The bands above 1500 cm⁻¹ (O–H, N–H, C–H, C=O) are the ones you read directly to spot functional groups.

// REFERENCES & FURTHER READING

Wikipedia — Spectroscopy ↗ Wikipedia — Mass spectrometry ↗ Wikipedia — NMR spectroscopy ↗

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