BRAINCAKENuclear Magnetic Resonance
Nuclear magnetic resonance (NMR) spectroscopy is used to work out the structure of organic molecules. It works for nuclei with an odd number of nucleons, such as 1H and 13C, which have a property called nuclear spin. 12C has an even number of nucleons, so it has no spin and gives no NMR signal.
A spinning nucleus behaves like a tiny magnet. In a strong external magnetic field it can line up with the field (lower energy) or against it (higher energy). Nuclei in the lower energy state can absorb radio frequency radiation of exactly the right energy to flip into the higher energy state. This absorption is called resonance.
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Key terms in this lesson
- tms
- Tetramethylsilane, Si(CH3)4, the reference compound added to an NMR sample, whose single peak defines a chemical shift of zero.
- chemical shift
- The position of a signal in an NMR spectrum, measured in parts per million relative to TMS, determined by how shielded the nucleus is by electrons.
More in Modern Analytical Techniques
- Thin-Layer Chromatography
- High Performance Liquid Chromatography
- Gas Chromatography
- Retention Times
- Chemical Shift
- 13C NMR Spectroscopy
- 1H NMR Spectroscopy
- Integration Traces
All 15 lessons in Modern Analytical Techniques · All Edexcel A-level Chemistry topics