3.3.15 Nuclear magnetic resonance spectroscopy (A-level only)
Appreciation that scientists have developed a range of analytical techniques which together enable the structures of new compounds to be confirmed.
Nuclear magnetic resonance (NMR) gives information about the position of 13C or 1 H atoms in a molecule.
13C NMR gives simpler spectra than 1 H NMR.
The use of the δ scale for recording chemical shift. Chemical shift depends on the molecular environment.
Integrated spectra indicate the relative numbers of 1 H atoms in different environments.
1 H NMR spectra are obtained using samples dissolved in deuterated solvents or CCl4 The use of tetramethylsilane (TMS) as a standard.
Students should be able to:
• explain why TMS is a suitable substance to use as a standard
• use 1 H NMR and 13C NMR spectra and chemical shift data from the Chemistry Data Booklet to suggest possible structures or part structures for molecules
• use integration data from 1 H NMR spectra to determine the relative numbers of equivalent protons in the molecule
• use the n+1 rule to deduce the spin–spin splitting patterns of adjacent, non-equivalent protons, limited to doublet, triplet and quartet formation in aliphatic compounds.