Science Section
Level 3 Extended Diploma in Applied Science
Practical Chemical Analysis
NMR Spectrum
Worksheet 1 - Answers
This exercise:
Chemical shift

Effect of highly electronegative atoms on chemical shift

1H

No splitting this time
environments
For each 1H NMR spectrum, find the molecular structure that matches.
Remember to refer to your booklet and leaflets for information.
Write:1. What you believe the structure is.
2. The name of the organic substance.
3. The H atom(s) that are responsible for each peak. Drawing part of the structure may
help, with the responsible hydrogen atoms highlighted.
4. Notes and observations
1H
NMR spectrum
Structure of Molecule
Notes and Observations
Name:
Not much going on here! There is just one H environment and
the signal has a chemical shift of around 0.2. The interpretation
table suggests a CH3 group that is not attached to or close to
an atom that is highly electronegative.
Methane
1H
NMR spectrum
(an alkane)
Structure of Molecule
Notes and Observations
Name:
There is just one H environment in the molecule. The signal
has shifted to the left, so there must be a highly electronegative Chloromethane
atom connected. Chlorine is the top candidate, since an O or N
atom would give you another H environment.
(a halogenoalkane)
2
1H
NMR spectrum
Structure of Molecule
-OH signal appears
anywhere in this range
Notes and Observations
There are two H environments in this molecule, so there are
two signals. The one caused by CH3- hydrogen atoms is
shifted to the left because of the O atom that is highly
electronegative. However, the other signal is caused by the
–OH hydrogen atom and is weaker than might be expected,
which is typical. Like the interpretation tables suggest, the
chemical shift can vary between 0.5 and 5.
1H
NMR spectrum
Name:
Methanol
(an alcohol)
Structure of Molecule
-NH2 signal appears
anywhere in this range
Notes and Observations
There are two H environments in this molecule, so there are
two signals. The one caused by CH3- hydrogen atoms is
shifted to the left because of the N atom that is highly
electronegative. However, the other signal is caused by the
–NH2 hydrogen atoms and is weaker than might be expected,
which is typical. Like the interpretation tables suggest, the
chemical shift can vary between 1.0 and 4.5.
3
Name:
Methylamine
(an amine)
1H
NMR spectrum
Structure of Molecule
Notes and Observations
There is only one environment here. This is because the
molecule is symmetrical such that all the hydrogen atoms are
equivalent. The chemical shift implies that a highly
electronegative atom is nearby and this becomes clear when
the table is consulted.
1H
NMR spectrum
Name:
Propanone
(a ketone)
Structure of Molecule
Notes and Observations
Name:
There are two H environments in this molecule, so there are
two signals. The signal intensities are easily to interpret when
Ethanal
the H atoms are connected to C atoms. As the table indicates,
the signal at 9.5 must be the lone H atom. The signal intensity
(an aldehyde)
(height/peak area) confirms this. On the right, the signal
intensity is three times as great, which indicates three H atoms.
The chemical shift is around that indicated in the table.
4
1H
NMR spectrum
Structure of Molecule
Notes and Observations
Two H environments again, this time with a very weak signal at
around 11.8. This is weak since the H atom is not connected to
a C atom. Also, the chemical shift is way out on the left, which
indicates that the H atom must be connected to a very
electronegative atom. Looking at the table, it must be the
carboxylic acid group and the chemical shift is so great
because there are two highly electronegative atoms involved
(both oxygen here). The other signal is predicted by the table.
1H
NMR spectrum
Name:
Ethanoic acid
(a carboxylic acid)
Structure of Molecule
Notes and Observations
There are two H environments yet again. According to the
table, the CH3- group connected to the O atom will have the
higher chemical shift. This makes sense since the group is
closer to a highly electronegative atom. The intensities are
equal as each environment has an equal number of H atoms.
Structures – but not in order:
5
Name:
Methyl ethanoate
(an ester)