NMR

Question 1

how is NMR carried out

Answer 1

• sample is dissolved in a solvent which doesnt have any ¹H atoms present
• add a standard which is added and the peak is set to 0 ppm making all the other peaks measured relative to the TMS peak
• either a carbon (¹³C) or proton (¹H) NMR is carried out

Question 2

how do you decide what solvent you use in NMR

Answer 2

• if the sample is polar use CDCl₃
• if the sample is non-polar use CCl₄

Question 3

why is deuterium used instead of H in the solvent

Answer 3

• the nucleus of H is NMR active meaning it would interfere with the spectrum of the compound that is being analysed

Question 4

why is TMS (tetramethylsilane) added to the sample

Answer 4

• non-toxic
• inert
• gives the peak in both ¹H or ¹³C NMR because all carbons/hydrogens in the same environment

Question 5

what does the ¹³C NMR tell you

Answer 5

• the amount of peaks tells you the amount of C environments
• the shift that each peak is in the tells you its environment

Question 6

what does the ¹H NMR tell you

Answer 6

• the number of peaks is the number of H environments
• integration value shows the relative number of H in each environment
• splitting pattern shows n+1 amount of H on adjacent carbon1