32 structure determination Flashcards
1
Q
what is NMR spectroscopy used for?
A
to determine structures of unknown organic substances
2
Q
why is NMR a powerful technique?
A
- it is easy to obtain a spectrum
- only a small amount of sample needed
- non-destructive
3
Q
why is carbon-13 used for NMR?
A
odd number of nucleons needed for a residual spin
4
Q
what are two things you need to be able to interpret in a carbon-13 NMR?
A
- number of peaks tells you number of C environments
- location of peaks tells you the type of C environment
5
Q
what is used as a reference standard for chemical shifts?
A
tetra methyl silane (TMS)
6
Q
what is the structure of TMS?
A
silicon surrounded by 4 methyl groups
7
Q
why is TMS used as a standard?
A
- generates one sharp peak
- unreactive
- highly volatile
- peak always found on far right of spectrum
8
Q
why is it good that TMS is unreactive?
A
so it won’t affect the sample being tested
9
Q
why is it good that TMS is highly volatile?
A
it can be removed from the sample after the analysis
