Laboratory Report
Organic chemistry practical course (OCP1)
HS 07/08
29.10.2007
Lorenz Schwarzer
D-Biol
Assistant: Zhu Liang
Synthesis of Aspirin
(Acetyl salicylic acid)
O
OH
O
CH3
O
Method
Acid-catalyzed esterification of an alcohol group:
Esterification of salicylic acid with acetic anhydride to acetyl salicylic acid, catalyzed
by sulfuric acid.
Reaction equation
O
O
OH
O
H2SO4
+
CH3

O
HO
O
OH
O
salicylic acid
acetic anhydride
O
acetyl salicylic acid
Mechanism
O
H
O
O
O
C
OH
+
O
+
H
+
O
O
OH
H
+
O
H
H
HO
O
OH
OH
O
O
O
+
O
C
O
O
+
C
H
O
O
OH
+
O
OH
H
O
-H2O
C
-H+
O
C
O
O
2
Physical properties of the substances
Salicylic acid
Molar weight
Density
Melting point
Boiling point
R-Phrases
O
138,12 g/mol
1,44 g/ml
158-161
°C
°C
R22 Harmful if swallowed,
R37/38 Irritating to respiratory system
and skin
R41 Risk of serious damage to the
eyes.
S26 In case of contact with eyes rinse
and seek medical advice.
S39 Wear eye/face protection
OH
OH
S-Phrases
Acetic anhydride
Molar weight
Density
Melting point
Boiling point
R-Phrases
O
102,08
1.08
138-140
R10
R20
R22
R34
S26
Flammable
Harmful by inhalation.
Harmful if swallowed.
Causes burns
In case of contact with eyes, rinse
immediately with plenty of water
and seek medical advice.
S36/37/38 Wear suitable protective
clothing
S45 In case of accident or if you feel
unwell, seek medical advice
immediately
O
S-Phrases
O
g/mol
g/ml
°C
°C
Sulphuric acid (H2SO4)
O
O
Molar weight
Density
Melting point
Boiling point
R-Phrases
S-Phrases
98,07 g/mol
1.84 g/ml
10
°C
338
°C
R35 Causes severe burns
S1/2 Keep locked up and out of the
reach of children
S26 In case of contact with eyes, rinse
immediately with plenty of water
and seek medical advice.
S30 Never add water to this product
S45 In case of accident or if you feel
unwell, seek medical advice
immediately
S
HO
OH
3
Acetyl salicylic acid (Aspirin)
Molar weight
Density
Melting point
Boiling point
R-Phrases
S-Phrases
CH3
HO
R22
S22
O
O
180,16
1.40
138-140
decomposes
Harmful if swallowed,
Do not inhale dust
g/mol
g/ml
°C
°C
O
Educts
First trial
Substance
Amount
Molar amount
g
4.06
~18
Salicylic acid
Acetic anhydride
Sulfuric acid
Volume
mol
0.0293
~0.19
ml
10 drops
~10
Second trial
Substance
Salicylic acid
Acetic anhydride
Sulfuric acid
Amount
Molar amount
g
3.15
~18
mol
0.0228
~0.19
Volume
ml
10 drops
~10
Experimental accomplishment
1. Salicylic acid and acetic anhydride were put into a 100ml round bottom flask.
10 drops of sulphuric acid were added. The solution was heated up to 80-90°C
for 20min (second time 1h).
2. To hydrozyze the unreacted acetic anhydride, 2ml deionised water was added.
3. The flask was cooled down in an ice bath. To crystallize, it was helped by
scratching. 25ml of ice water was added.
4. The crystals were filtered with vacuum and washed with ice water.
5. The crystals were dried on a filter paper.
6. The infrared spectrum was measured.
4
Experimental setup
Reflux condenser
Thermometer
Filter
Oilbath
4
3
21
5 67
8
11 9
4
3
2
1
5 67
8
9
1
0
Vacuum
Heating apparatus
Filtration apparatus
Results
IR-Spectrum-bands [cm-1]
3200-3500
2500-3600
1735-1750
O-H stretch (alcohols)
O-H stretch (carboxylic acids)
C=O stretch (esters)
After one procedure, the product was only salicylic acid. So I tried it again, but with
the aid of the comparisons of the token IR-spectrum with the reference spectra of
salicylic acid and aspirin, you can see that most of the product is still salicylic acid.
But there is one little top at 1749.91, so at least a little bit of aspirin is originated from
salicylic acid.
5
IR-Spectrum of the Product (second trial)
Reference IR-spectrum of salicylic acid
6
Reference IR-spectrum of Aspirin
Literature




http://riodb01.ibase.aist.go.jp/sdbs/cgi-bin/cre_index.cgi?lang=eng
http://en.wikipedia.org
http://www.chemexper.com
http://www.chemblink.com
7