NMR
Benchtop NMR for
Educational Experiments
Esterification Reaction
This experiment is designed to teach the practical aspects and principles of the Fischer
esterification reaction:
Refluxing, isolation of organic compounds, purification by distillation.
Total experiment time: 2 hours
The esterification reaction involves the reaction of a carboxylic acid with an alcohol.
The reaction is a reversible reaction taking place under acidic conditions with the application of heat.
An example is the reaction of 3-methyl-1-butanol with glacial acetic acid to form isoamyl acetate. The reaction is performed
using sulphuric acid as a general acid catalyst using an excess of glacial acetic acid:
O
+
OH
O
H2SO4
O
+ H2O
HO
Pulsar™, a 60MHz benchtop NMR
spectrometer can be used to measure
O
X
the spectra of the starting materials
O
+ H2O
and reaction product confirming that
the reaction has completed and no
Nu
X Nu
Nu−
O
H2SO4
+
OH
HO
starting materials remain. The spectra
X−
of the starting materials glacial acetic
O
Y
Y
O
O
+
N
O
+
N
Y
O
+
N
O
+
O
+
N
H2N
Br
NH
O
H2N
OH
r
+
N
O
+
N
+
NH
O
Br
O
+
O
O
+
NH
+
N
O
O
+
N
CH3
CH3
H3C
O
+
O
Br
with the final product isoamyl acetate
Figure 1. From top to bottom: Glacial
acetic acid, 3-methyl-1-butanol and isoamyl
acetate spectra
O
+
N
O
Y
O
Y
+ H2O
acid and 3-methyl-1-butanol, along
are shown in Figure 1.
O
X−
+
N
O
+ H2O
+
N
X− O-
O
Nu
Y
O
H2N
HO
X Nu
Nu−
+
O
O
Nu
X Nu
Nu−
O
H2SO4
Br
+
OH
+
OH
HO
X
O
+
N
O
H2SO4
It is clear from these spectra that neither glacial acetic acid nor 3-methyl-1-butanol is present in the spectrum of isoamyl acetate. The
isoamyl acetate has tetramethylsilane (TMS) added as a chemical shift reference material showing a peak at 0ppm chemical shift.
The student can assign the peaks in the spectrum and generate peak integrals in order to verify the identity of the reaction product.
Pulsar is a cryogen-free benchtop NMR spectrometer that can easily be sited in the
undergraduate chemistry laboratory allowing hands-on NMR for students.
A simple to use software interface and standard sampling using 5mm NMR tubes enables
a high throughput of samples in a busy laboratory.
Contact us now for more information
industrial@oxinst.com
for more information visit www.oxford-instruments.com/pulsar
2927
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