NMR spectroscpy

Question 1

what is NMR

Answer 1

an analytical technique to determine and understand the structure of molecules

Question 2

types of NMR

Answer 2

C13 - provides information of carbon atoms within a molecule
H1 - provides information of hydrogen atoms within a molecule

Question 3

how does NMR work

Answer 3

NMR uses atomic nuclei that have an odd number nucleus in order to exhibit nuclear spin, this causes the nucleus to act like a magnet.

Question 4

C13 spectrum

Answer 4

each peak shows us each carbon environment

Question 5

H1 spectrum

Answer 5

each peak shows us each hydrogen environment

Question 6

H1 NMR - splitting and integration

Answer 6

the integration value tells us the ratio of hydrogens of each peak
the splitting patten tells us the number of hydrogens on the adjacent carbons
singlet - no hydrogens on the adjacent carbon
doublet - one hydrogen on the adjacent carbon
triplet - two hydrogens on the adjacent carbon
quartet - three hydrogens on the adjacent carbon

Question 7

exceptions to the splitting patterns

Answer 7

a hydrogen bonded to a nitrogen or an oxygen will display as a singlet no matter the number of adjacent

Question 8

solvents used in NMR

Answer 8

samples are dissolved in inert solvents that contain no H atoms
e.g. CCl4 or CDCl3
as they have not H atoms they will not form a peak on H1 NMR
CCl4 is non polar so used for non-polar molecules
CDCl3 is polar so is used for polar molecules.

Question 9

calibration of the NMR spectrum

Answer 9

tetrameythllsilane (TMS) is added to calibrate the spectrum.
TMS is used as it only forms one peak at the very right of the spectrum.
it is non toxic
it is inert
it has a low boiling point so can be removed
each carbon and hydrogen are in the same environment