BRAINCAKENMR Spectroscopy
Revision notes for NMR Spectroscopy in OCR Chemistry A (H432). 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 the most powerful technique for finding the structure of an organic molecule.
- Chemical ShiftThe position of an NMR peak is given by its chemical shift, symbol δ, measured in parts per million (ppm).
- The TMS StandardNMR chemical shifts are measured relative to a standard, tetramethylsilane, TMS, formula Si(CH3)4.
- Deuterated SolventsFor NMR, the sample is dissolved in a solvent.
- 13C NMR Spectroscopy13C NMR spectroscopy gives information about the carbon skeleton of a molecule.
- Interpreting 13C NMR SpectraTo interpret a 13C NMR spectrum, first count the peaks (ignoring TMS at 0 ppm) to find the number of carbon environments, then use each chemical…
- 1H NMR SpectroscopyProton (1H) NMR spectroscopy gives information about the hydrogen atoms in an organic molecule.
- Relative Peak AreasIn a 1H NMR spectrum the area under each peak is proportional to the number of hydrogen atoms in that chemical environment.
- Spin-Spin SplittingIn a high-resolution 1H NMR spectrum, many peaks are not single lines but are split into a cluster of smaller peaks.
- The n+1 RuleThe number of sub-peaks in a split 1H NMR peak is given by the n+1 rule: number of sub-peaks = n + 1 where n is the number of protons on the…
- Identifying O-H and N-H Protons with D2OProtons in O-H (alcohols, carboxylic acids) and N-H (amines, amides) groups are hard to identify from a 1H NMR spectrum: • their chemical shift…
- Combining Techniques to Deduce StructuresNo single technique proves a structure.