3.15 NMR Spectroscopy
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Which atoms produce a signal in NMR spectrums?
Atoms with odd mass number (as they have nuclear spin)
How does NMR spectroscopy work?
• Sample placed in a magnetic field • Atoms with odd mass number align with / against the field • Radio waves passed through the sample • Nuclei absorb energy and flip between nuclear spin states • Energy required for resonance is detected
Why multiple peaks produced by the same element in an NMR spectrum?
Different chemical environments require different amounts of energy for nuclei to flip between states
Which solvents are used for NMR spectroscopy?
CDCl₃ (Deuterated solvents) - Polar compounds CCl₄ - Non polar compounds
Molecule used as a reference standard in NMR spectroscopy
TMS (Tetramethylsilane) Silicon with 4 methyl groups attached
Why is TMS used as a reference standard?
• Unreactive and non-toxic • Volatile so easy to remove • Produces a peak far away from other signals