NMR

Question 1

What does NMR stand for?

Answer 1

Nuclear magnetic resonance.

Question 2

What is resonance

Answer 2

electrons have two different spin states with different energies. when an atom is given the correct magnetic field strength and the correct radio frequency radiation, the nucleus can absorb energy and will flip between the two spin states.

Question 3

NMR spectrometer measure the amount of __ __ absorbed in the __

Answer 3

radio waves
nuclei

Question 4

Most organic molecules contain hydrogen and carbon molecules. most carbon molecules are C12 but about 1.1% are C13. why is it important for NMR that H1 and C13 are present for it to work.

Answer 4

this is because they have an odd number of protons and neutrons so the nucleus has SPIN.

Question 5

True or False
in different environments nuclei absorbs the same amount of energy to resonate

Answer 5

False - in different environments, slightly different amounts of energy are absorbed to resonate.

Question 6

what is the unit of a C13 chemical shift relative to TMS
what is TMS

Answer 6

ppm - parts per million
tetramythlsilane and it is used a standard reference point to calibrate NMR scale = 0ppm

Question 7

what does the number of peaks tell us?

Answer 7

The number of different carbon environments

Question 8

what does the position of the peaks tell us

Answer 8

the type of carbon environment which you can use your data sheet to work out

Question 9

the sample must be dissolved in a solvent. give and example.

Answer 9

CDCl3 - gives a signal but the machine can recognise it and easily remove it from the spectrum