NMR spectroscopy Flashcards
What are the two types of NMR spectroscopy?
13C NMR
1H NMR
What causes different nuclear environments?
A nucleus is partly shielded from the effects of an external magnetic field by the surrounding electrons.
Any other atoms and groups of atoms that are around a nucleus will also affect the amount of electron shielding
Overall effect of the external magnetic field on each nucleus is different, depending on the environment within the molecule
What happens to nuclei in different nuclear environments?
They absorb different frequencies which is what causes the results in the NMR spectroscopy
What is the chemical shift?
the differences in the frequencies absorbed by the molecules in different environments, relative to a standard substance
What standard substance is used?
Tetramethylsilane (TMS)
What is the structure of TMS?
One Si surrounded by 4 CH3 groups
Why is TMS used as a standard substance?
- it has 12 hydrogens in identical environments
- it has 4 carbons all in identical environments
- produces one absorption peak
What characteristics of TMS make it good to use as a standard substance?
Inert
Non-toxic
Volatile
