3.3.15-NMR

Question 1

What is NMR

Answer 1

A very powerful tool for identifying compounds radio waves pass through and produce a spectrum

Question 2

How to identify number of signals

Answer 2

One signal for each equivalent H atoms

Question 3

How to find relative intensity

Answer 3

The ratio of each equivalent H atoms in each signal

Question 4

Explain chemical shift

Answer 4

Chemical shift depends on what other H atoms are near

Question 5

Explain spin spin splitting

Answer 5

Number of lines in signal gives information about neighbouring H atoms. If there are same carbon atoms there is no splitting

Question 6

Equation for number of lines

Answer 6

1 + number of non-equivalent H atoms on adjacent C atoms

Question 7

Singlet
Show appearance
N of line
Neighbouring non equiv

Answer 7

Draw

Question 8

Doublet 
how appearance 
N of line 
Neighbouring non equiv 
Relative size

Answer 8

Draw

Question 9

Triplet 
how appearance 
N of line 
Neighbouring non equiv 
Relative size

Answer 9

Draw

Question 10

Quarter 
how appearance 
N of line 
Neighbouring non equiv 
Relative size

Answer 10

Draw

Question 11

What is it called if signal is bigger than 4

Answer 11

Multiplet

Question 12

What happen to H atoms on OH groups

Answer 12

OH groups do not have any splitting

Question 13

Draw graph

Answer 13

Have to measure to find ratios

Question 14

What solvents are used in NMR and why

Answer 14

Solvents are used that do not contain any H atoms they should have no nuclear spin
Eg CDCL3 , C6D6, CCl4

Question 15

What is used to calibrate NMR and why

Answer 15

TMS provides an internal standard to compare other peaks to

Question 16

Why is TMS used

Answer 16

• Gives a signal that is further right than most signals (because of low electro negativity of Si)
• only gives one signal as all 12 atoms are equivalent
• it is non toxic
• it is inert
• low boiling point so can be easily removed