NMR Spectroscopy Flashcards
What type of nucleus can be analysed by NMR?
Nuclei with spin e.g. C13
How does NMR determine the number of carbon environments in a molecule?
Whenever molecules are placed in a magnet, each carbon-13 environment will have a certain frequency of radio wave which causes its nuclei to switch spin states.
If two carbon atoms are in the same environment, their energy gaps will be the same.
What do we add to the sample before we start each NMR?
Standard - this is tetramethylsilane (TMS)
Why is TMS used as the standard?
- Only has 1 carbon environment - will only show 1 peak.
- TMS won’t interfere with any other molecules in sample.
- Non-toxic
What does number of peaks show in NMR spectra?
Number of carbon environments
What can peak height show in NMR spectra?
How many carbons are in that environment - not very reliable
What does the relative peak area show in H NMR?
How many hydrogens are in each environment
How many neighbouring hydrogens does a hydrogen that produces a singlet peak have?
0
Outline the n + 1 rule
The peak produced by any given hydrogen environment is split into the number of neighbouring non-equivalent hydrogens +1.
What are the standard and solvents used in H NMR?
Standard = TMS
Solvent = deuterated solvents e.g. D2O because they don’t interfere with NMR
Why are O-H and N-H only singlets?
They don’t split
