A level chemistry AQA A2 Proton NMR- quick review for class

1. A2 Chemistry
Quick Guide
High Resolution 1H
Nuclear Magnetic
Resonance
Spectroscopy
https://www.youtube.com/watch?v=uNM801B9Y84

2. High Resolution 1H Nuclear Magnetic Resonance Spectroscopy
10  0
Energy
Absn.
TMS
 3 different environments of 1H nuclei, thus 3 nmr signals
Reminder: CH3-CH2-CO-CH3
CH3 CH2 CH3
At high resolution nmr, signals are seen to be split.
10  0
Absn. TMS
Are there >1 1H nuclei environment in CH3COCH3 and
what will the integration number be for the signal(s)?

3. Proton NMR Spectra
 Number of environments = number of
peaks
 Number of protons in environment =
relative peak area (integral)
 Number of protons on neighbouring
carbon = splitting pattern (eg. doublet,
triplet)
 Type of proton environment = chemical
shift (compare with datasheet)

4. The “n+1” Rule
The signal produced by a H group which has “n” H atoms
on its neighbouring atom is split
into “n +1” signals.
The relative heights of the peaks give the relative number
of hydrogen atoms for that particular H environment.
• If there is only 1 peak for the molecule, no integration
number is recorded
• If peaks have identical numbers of hydrogen atoms
then their integration ratios will be 1:1:1:1 etc
A molecule will produce a single nmr signal for ALL
hydrogen atoms located within the same environment

5. LOW RESOLUTION
nmr
HIGH RESOLUTION
nmr
Caused by
how many H
neighbours?
Singlet 0
Doublet 1
Triplet 2
Quartet 3
Described
as a
1:1
1:2:1
1:3:3:1
SUMMARY OF SPLITTING PATTERNS

6. Example:
10 
CH3-CO-O-CH2-CH3
CH3CH2 CH3
(a) (b) (c)
What is this?
RCO-CH 2.1-2.6 Int. 3 singlet
RCO-O-CH 3.7-4.1 Int. 2 quartet
R-CH3 0.7-1.2 Int. 3 triplet
2 3 3 TMS
0

7. Example:
10 
CH3-CO-O-CH3
CH2 CH3
(a) (b)
What is this?
RCO-CH 2.1-2.6 Int. 3 singlet
RCO-O-CH 3.7-4.1 Int. 3 singlet
2 3 TMS
0

8. Patterns to look for :
(a) 2 doublets
 W―CH―CH―Z
X Y
│ │
(b) 2 triplets
 W―CH2―CH2―Z
(c) Triplet and
quartet
 W―CH2―CH3
(d) Triplet and
doublet
(e) Doublet and
quartet
 W―CH―CH2
X Y
│ │
 W―CH―CH3
X
│
W , X , Y and Z = atom with NO H bonded to it
Quartet
Triplet
Triplet
Doublet
Quartet
Doublet

9. SPLITTING BY
NEIGHBOURING OH and NH
GROUPS-usually NONE
10  0
Absn. TMS
RCH3 0.7-1.2 Int. 3 triplet
R-O-CH 3.1-3.9 Int. 2 quartet
R-OH 0.5-5.0 Int. 1 singlet*
Example: CH3-CH2-OH
(a) (b) (c)

10. Two 1H nmr spectra shown below were obtained from compounds X and Y, both
containing just one functional group and having the molecular formula, C3H6O2.
Deduce the structures of X and Y.
Possible structures?
(a) CH3CH2COOH
(b) CH3COOCH3
(c) HCOOCH2CH3
X Y
 3 signals, Integration: 3:2:1
Triplet, quartet, singlet
δ 0.7-1.2, 2.1-2.6, 10.0-12.0
 2 signals, Integration: 1:1 to each other
Both singlets
δ 2.1-2.6 and 3.7-4.1
 3 signals, Integration 1:2:3
Singlet, quartet, triplet
δ 9.0-10.0, 3.7-4.1, 0.7-1.2
= Y
= X

11. 4.0
ppm
2.2ppm
1.2ppm
2-propanol

12. 9.8
ppm
2.2 ppm
Ethanal

13. Ethyl ethanoate
4.1
ppm
2.0ppm
1.3ppm

14. Draw a Proton NMR to represent 1-
Bromopropane