BRAINCAKENMR Spectroscopy
Revision notes for NMR Spectroscopy in AQA Chemistry (7405). Read the start of any lesson here, then sign in free for the whole lesson, the R.E.C.I.P.E. recall steps and the quiz.
- Nuclear Magnetic ResonanceNuclear magnetic resonance (NMR) spectroscopy is an analytical technique that gives information about the position of 13C or 1H atoms in a molecule.
- Chemical ShiftIn an NMR spectrum, the position of a peak is given by its chemical shift, symbol δ, measured in parts per million (ppm).
- The TMS StandardChemical shifts are measured relative to a reference compound, tetramethylsilane (TMS), Si(CH3)4.
- Deuterated SolventsNMR spectra are usually recorded with the sample dissolved in a solvent.
- 13C NMR Spectroscopy13C NMR spectroscopy gives information about the carbon atoms in a molecule.
- Interpreting 13C NMR SpectraTo work out a structure from a 13C NMR spectrum, use two pieces of information: the number of peaks and the chemical shift of each peak.
- 1H NMR Spectroscopy1H NMR spectroscopy (proton NMR) detects the hydrogen nuclei in a molecule.
- Integration TracesIn a 1H NMR spectrum, the area under each peak is proportional to the number of H atoms in that environment.
- Spin-Spin SplittingIn a high-resolution 1H NMR spectrum, many peaks are not single lines.
- The n+1 RuleThe n+1 rule links the splitting of a 1H NMR peak to its neighbours: H atoms with n H atoms on the adjacent carbon(s) give a peak split into n + 1…
- Interpreting 1H NMR SpectraTo deduce a structure from a 1H NMR spectrum, combine all four pieces of information with the molecular formula: • Number of peaks: the number of H…