3.15 NMR

Question 1

What isotope of carbon is used in CNMR?

Answer 1

Carbon 13

Question 2

On a Carbon NMR spectrum what information can be obtained?

Answer 2

• The number of peaks = number of carbon environments
• Chemical shift of atom = how close to an EN atom the carbon is

Question 3

What information can be obtained from proton NMR?

Answer 3

• Number of peaks=number of H environments
• integration/height of peaks/relative intensity= number of H in each environment (when in simplest ratio)
• Chemical shift= proximity to en atom
• splitting= number of H on adjacent atom

Question 4

What is the n + 1 rule?

Answer 4

N= number of H on adjacent atom

Question 5

What solvents are used in NMR?

Answer 5

CDCl3 or CCl4

Question 6

Why are the solvents in NMR used?

Answer 6

• Creates a peak on far left which can be ignored in C 13 NMR and not shown in H NMR
• CCl4 dipoles cancel out creating non polar molecules ,used for non polar solvents
• CDCl3 is a polar molecule and is used for polar molecules

Question 7

What is TMS used for and what does it stand for?

Answer 7

• Tetramethylsilate
• Used to calibrate spectrum

Question 8

Why is TMS used in NMR?

Answer 8

• Only gives 1 peak
• No EN
• Inert
• Volatile
• Non toxic