32- structure determination

Question 1

what does NMR stand for

Answer 1

nuclear magnetic resonance spectroscopy

Question 2

why do carbon atoms with different functional groups feel the magnetic field differently/ resonate differently

Answer 2

this is because all nuclei are shielded from the external magnetic field by the electrons that surround them (nuclei with more electrons = better shielding = lower frequency resonated)

Question 3

what is chemical shift

Answer 3

it is measure in parts per million and is related to the difference in frequency between the resonating nucleus and that of TMS

Question 4

howe is the chemical shift calibrated

Answer 4

using TMS

Question 5

why is TMS used to calibrate chemical shift

Answer 5

it is:
- inert
- non-toxic
- all C and H are in the same environment

Question 6

what is an integration trace

Answer 6

it is found in H NMR spectra and represents the number of hydrogen atoms representing each peak

Question 7

what is spin-spin splitting

Answer 7

splitting of peaks which gives information of neighboring hydrogen atoms

Question 8

what is the rule used for splitting in H NMR

Answer 8

n + 1

Question 9

why must solvents for NMR not contain any hydrogen atoms

Answer 9

because the signal from the hydrogen atoms in the solution would swamp the signal from the hydrogen atoms as there is vastly more of them

Question 10

what deuterium

Answer 10

an isotope of hydrogen that does not produce an NMR signal