Spectroscopy

Question 0

How can you work out the number of non-equivalent protons adjacent to a given proton?

Answer 0

From the spin-spin splitting pattern, using the n+1 rule eg if a proton has 1 non-equivalent adjacent proton, the peak will split into 2

Question 1

NMR spectroscopy involves…

Answer 1

Interaction of materials with the low-energy radiowave region of the electromagnetic spectrum

Question 2

Why is TMS used in NMR?

Answer 2

As a standard to measure chemical shifts against
It has a chemical shift of 0ppm, is chemically unreactive and volatile so easily removed from a sample after the spectrum has been run

Question 3

What is suitable solvent for NMR and why?

Answer 3

CDCl3 is usually used
D is an isotope of hydrogen with one proton and one neutron. It has an even mass number and so doesn’t produce a signal on the spectrum

Question 4

What is D2O used for?

Answer 4

It is added to a mixture and an NMR spectrum is run

Absorptions due to -OH and -NH protons can be easily identified, because these peaks disappear when D2O is added