A-Level Chemistry Specification

AQA 7405

Section 3.15: Nuclear magnetic resonance spectroscopy

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#3.15.1

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 1H atoms in a molecule.

13C NMR gives simpler spectra than 1H 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 1H atoms in different environments.

1H 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
- buse 1H 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 1H 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.