6.3 Analysis (completed)

Question 1

What is used to provide the standard peak in NMR spectroscopy?

Answer 1

Tetra Methyl Silane (TMS)

Si(CH3)4

Question 2

Why does TMS provide a good standard?

Answer 2

Non-toxic liquid
Inert - doesnt react with compound being analysed
Low boiling point - can be distilled off and reused
All hydrogen and carbon atoms chemically equivalent so only one peak at δ = 0 is produced

Question 3

What produces different peaks on C13 NMR spectroscopy?

Answer 3

Carbon atoms in different chemical environments

Question 4

What is 1H NMR also known as?

Answer 4

Proton NMR spectroscopy

Question 5

What is the height of the peak in 1H NMR spectroscopy?

Answer 5

The height of the peak is proportional to the number of atoms in the same chemical environment

Question 6

What is the difference between high and low resolution 1H NMR show?

Answer 6

Both show:
The number of different chemical environments
The relative number of hydrogen atoms in each environment
High resolution also shows the number of neighbouring hydrogens to that environment

Question 7

What is the n + 1 rule?

Answer 7

The peak on a high res 1H NMR is split into the number of adjacent hydrogens plus one
Producing a doublet, triplet, quartet, multiplet

Question 8

What is the D2O shake?

Answer 8

It is used to idenify if a peak is due to a -OH group or -NH group.
Add as small amount of D2O and then re-run the spectrum, any signal due to -OH protons disappear