3.15 Nuclear Magnetic Resonance Spectroscopy

Question 1

What is nmr?

Answer 1

Nuclear magnetic resonance spectroscopy

Question 2

What is used in nmr?

Answer 2

Solvent

Standard

Question 3

What kind of solvents are used in nmr?

Answer 3

Free of H atoms (protons)

CDCl3

D = deuterium

Question 4

Why is a standard used?

Answer 4

To calibrate it (zero it)

Compounds are measured against a standard molecule

TMS - tetramethylsilane
Si(CH3)4

Question 5

Why is TMS used as a standard in nmr?

Answer 5

It’s signal is far away from the others only gives one signal
Non-toxic
Inert
Low boiling point - easy to remove

Question 6

What is a molecular environment in nmr?

Answer 6

There is one signal for each set of H atoms

The ‘groups’ of H atoms have to be discrete - if another group is attached to exactly the same then it could be the same environment

Question 7

What is the integration value in nmr?

Answer 7

The intensity of each signal being proportional to the number of equivalent H atoms it represents

Eg 3:2:1

Question 8

What is the n+1 rule?

Answer 8

n = number of adjacent non-equivalent protons

(In the next molecular environment)

Then you + 1

Question 9

What are all the n+1 names?

Answer 9

1 - singlet
2 - doublet
3 - triplet
4 - quartet
5 - multiplet

Question 10

What are the splitting patterns?

Answer 10

Using the n+1 rule put those numbers into a ratio