NMR

Question 1

Why can carbon-13 be analysed by NMR?

Answer 1

Has spin, unequal number of proton and neutrons.

Question 2

What is used as the standard (comparison)?

Answer 2

Reading of 0
TMS- tetramethylsilane

-inert
-non-toxic
-volatile
-same environments
-found to the far right of the spectrum

Si with 4 CH3 around it

Question 3

What is the solvent used and why?

Answer 3

Deuterated Chloroform (CDCl3)

doesn’t show a hydrogen peak

Question 4

What does each peak represent on a carbon NMR?

Answer 4

A different carbon environment

Question 5

What is carbon environment?

Answer 5

-Carbons with different bonds will feel the magnetic field differently

e.g. a carbon bonded to 3 hydrogens and one CH3, and another with the exact same bonds are in the same carbon environment.

If one had a Cl instead of a H, there would be 2 carbon environments.

Question 6

What are splitting patterns?

Answer 6

How proton (hydrogen) NMRs are shown:

1 peak- singlet
2 peaks- doublet
3 peaks- triplet
4 peaks- quartet

Question 7

What is the n+1 rule?

Answer 7

n= the number of hydrogens on adjacent carbon

gives you the splitting pattern of that proton environment.