NMR Spectroscopy

Question 1

What are the 2 types of spectroscopy

Answer 1

13C NMR
1H (proton) NMR

Question 2

How are peaks determined in 13C?

Answer 2

Number of different C environments

Question 3

How many 13C signals (peaks) would there be in propanal?

Answer 3

3

Question 4

How many 13C signals (peaks) would there be in 2-chloro,2-methylpropane?

Answer 4

2

Question 5

How many 13C signals (peaks) would there be in 1-methyl-4-nitrobenzene?

Answer 5

5

Question 6

How are peaks determined in 1H?

Answer 6

Number of different H environments

Question 7

How are ratios determined in H1

Answer 7

Number of H atoms on the neighbouring C atom

Question 8

How many 1H signals (peaks) and ratio would there be in 2-bromobutane?

Answer 8

4
3:1:2:3

Question 9

How many 1H signals (peaks) and ratio would there be in propene?

Answer 9

3
3:1:2

Question 10

Solvents used in NMR and why?

Answer 10

CCl4 - Inert, non polar for non polar molecules

CDCl3 - Inert, polar for polar molecules

Question 11

What is TMS?

Answer 11

Tetramethylsilane to calibrate the spectrum

Question 12

TMS properties

Answer 12

Gives one signal

Signal does not merge with other signals

Non-toxic

Inert

Low boiling point so easily removed

Question 13

How is splitting of peaks in 1H NMR decided

Answer 13

Number of inequivalent H’s on neighbouring C atoms + 1

Question 14

Peak of 1H NMR connected to an O or N molecule

Answer 14

Singlet peak

Question 15

State why Si(CH3)4, CCl4 and CDCl3 are used in 1H NMR spectroscopy.

Explain how their properties make them suitable for use in 1H NMR
spectroscopy. [6]

Answer 15

Stage 1 [1+2]
CDCl3 / CCl4 as solvent
TMS as reference / calibration
Inert

Stage 2 [3+4]
CDCl3 / CCl4 both have no H atoms
CCl4 non polar
CDCl3 polar covalent molecule

Stage 3 [5+6]
Gives one signal
Signal in an area away from other typical H signals
Low bp / easy to remove