6.3.2 - Spectroscopy

Question 1

What is used as the standard for NMR?

Answer 1

Tetramethylsilane (TMS)

Question 2

Why is TMS used?

Answer 2

It produces a single peak and is non toxic, volatile and inert.

Question 3

What does the standard do?

Answer 3

Gives a peak at 0.

Question 4

What does the sample need to be dissolved in?

Answer 4

A solvent.

Question 5

What is the problem with organic solvents?

Answer 5

They contain C and H so will produce peaks in the spectrum. Moreover the proton peaks will swamp the spectrum so the sample being investigated will not be seen.

Question 6

What solvent is instead used?

Answer 6

CDCl3 or C6D6

Question 7

Why are different solvents used?

Answer 7

They contain deuterium an isotope of hydrogen so will not give a peak in the NMR spectrum.

Question 8

What does the number of peaks show in carbon NMR?

Answer 8

The number of carbon environments.

Question 9

In proton NMR what does the number of peaks give?

Answer 9

The number of different proton environments.

Question 10

What does the integration tell us in proton NMR?

Answer 10

The number of protons responsible for the peak.

Question 11

What does the splitting pattern used for in proton NMR?

Answer 11

The number of protons on the neighbouring carbon.

Question 12

1 peak is called?

Answer 12

Singlet

Question 13

2 peaks are called?

Answer 13

Doublet

Question 14

3 peaks are called?

Answer 14

Triplet

Question 15

4 peaks are called?

Answer 15

Quartet

Question 16

What is the splitting pattern called if there are more than 4 peaks?

Answer 16

Multiplet.

Question 17

When does splitting not occur?

Answer 17

For identical proton. Identical protons do not split each other, e.g. ethane.

Question 18

What is significant about OH and NH peaks?

Answer 18

They are singlets, no splitting occurs.

Question 19

How can you confirm the presence of an OH and NH proton?

Answer 19

Add D2O and shake vigorously.

Question 20

Why does the peak disappear in the presence of D2O?

Answer 20

Deuterium doesn’t show up on the NMR spectrum.

Question 21

What does the proton peak generally look like for benzene?

Answer 21

Usually a complex multiplet is seen.

Question 22

For benzene protons what does integration 5 usually mean?

Answer 22

1 group attached to benzene.

Question 23

For benzene protons what does integration 4 usually mean?

Answer 23

2 groups attached to benzene.