Synthesis of Aspirin

This article discusses the synthesis of aspirin, including laboratory techniques, factors affecting yield, recrystallization, solvent extraction, and TLC analysis. It also explores the melting point and purity of aspirin samples. References are provided for further reading.

SYNTHEIS OF ASPIRIN 1
SYNTHESIS OF ASPIRIN
By (name)
The Name of the Class (Course)
Professor (Tutor)
The Name of the School
The Cite and State
The Date

SYNTHESIS OF ASPIRIN 2
Introduction
Aspirin is a chemical compound known as acetylsalicylic acid. It is a painkiller.
During aspirin synthesis, a strong acid (normally phosphoric acid) is applied as a catalyst.
Normally, the preparation of aspirin in the laboratory is the same as in industrial scale. This
report discusses the preparation of an aspirin sample in the laboratory, measuring its melting
point, and comparing it with a pure aspirin sample. Furthermore, the comparison between the
laboratory and industrial aspirin techniques were compared, and factors affecting aspirin
yield were discussed.
Laboratory techniques of preparation of aspirin
The aspirin synthesis is an esterification reaction which takes place between an ester
and an acid to yield a sophisticated ester.
C4H6O3 (aq) +C7H6O3 (aq) –> C2H4O2 (aq) + C9H8O4(s)
The experiment was performed in a fume hood. After adding 4cm3 of ethanoic
anhydride and five drops of 85% phosphoric (v) acid into 50cm3 pear-shaped flask which
contained 2.0g 2-hydroxybenzoic acid, the flask was fitted a reflux condenser and heated on
the steam bath for ten minutes while stirring the flask’s content. 2cm3 of water was added in
one portion down condenser without cooling the flask’s content. The mixture was poured into
40cm3 of cold water in 100cm3 beaker and cooled to room temperature while rubbing and
stirring inside the beaker. The mixture was placed in an ice bath. A butcher funnel was then
set-up for filtration of the flask’s content. During filtration, the mixture was washed with little
water.

SYNTHESIS OF ASPIRIN 3
2-hydroxybenzoic acid was the limiting reactant while ethanoic anhydride was an
excessive reactant. One mole of 2-hydroxybenzoic acid reacted with one mole of ethanoic
anhydride to yield one mole of acetylsalicylic acid and one mole of 2-hydroxybenzoic acid.
The theoretical yield is calculated from the reaction above. In the reaction, 2-
hydroxybenzoic acid and acetylsalicylic acid is in the ratio of 1:1. Therefore, they have the
same number of moles.
2.0 g
138.118 g /mol=0.01448 moles
Theoretical yield = (g=mol X MM) = (244.154g x 0.01448 moles) = 3.54g
Recrystallization
Recrystallization was achieved by first weighing the mass of the filtered aspirin
sample and sand. Boiling water and adding it to the filtered aspirin sample until it dissolved.
The dissolved mixture was filtered (gravity filtration) using a fluted filter when it was still
hot. The filtrate was cooled in air, followed by ice-bath. The cooled filtrate was re-filtered
using suction filtration and impurities on white crystals on filter paper were dissolved. The
white crystals were open dried in a safe place and its weight (3.21g) was taken.
Solvent extraction of aspirin
9cm3 of 3ml hydrochloric acid was added drop by drop to the aspirin mixture from the
condenser while testing the mixture pH using pH meter until its pH reached 3. At this pH, a
suspension was formed. The mixture was cooled in an ice bath, filtered and washed with cold
water. The extracted solid was completely dried in an open-air and weighed (3.03g).
Thin layer chromatography

SYNTHESIS OF ASPIRIN 4
0.05g of extracted aspirin sample was dissolved in 3cm3 methanol in a test-tube.
Additionally, 0.05g pure aspirin (standard aspirin) was also dissolved in 3cm3 methanol in
another test-tube. Furthermore, another 0.05g of recrystallized aspirin sample was dissolved
in 3cm3 methanol in a test tube. The sample was run separately in TLC (thin layer
chromatography) using 1-butyl ethanoic acid in the mobile phase. After the development of
TLC plates, TLC plates were placed in iodine chamber. The TLC plate was spotted with pure
aspirin, recrystallized aspirin, and crude aspirin at 1cm from the bottom of PLC plate. The
spots were placed at equal distance from each other. When there was no observation in the
movement of the solvent front, the TLC plate was removed from the iodine chamber and the
solvent marked. The plate was dried and assessed under UV light.
Aspirin sample The distance of the
solvent (cm)
Distance traveled by
the sample(cm)
Rf
Pure aspirin 3.2 2.6 0.8125
Recrystallized
aspirin
3.2 1.9 0.59375
Aspirin extracted by
solvent extraction
3.2 3.0 0.9375
Crude aspirin 3.8 3.5 1.08571
Table 1: TLC analysis of aspirin samples
The testing melting point and temperature of aspirin sample
Melting point test was conducted to obtain recrystallized and aspirin extracted
through solvent extraction were pure. The Mel-Temp instrument was employed in the
determination of aspirin melting point. The small size of vacuum filtered aspirin sample was
introduced into a capillary tube. The Mel-Temp temperature was connected to the capillary

SYNTHESIS OF ASPIRIN 5
tube to determine the temperature of the aspirin. The aspirin was pounded to enable
maximum heat absorption. The aspirin was warm gradually to curb thermometer explosion in
the Mel-Temp instrument. The aspirin liquidation showed that the melting point was attained.
The initial melting point was recorded at 137.5℃ and 157℃ when the aspirin sample fully
melted. Recrystallized had a melting point of 137.5℃. The same procedures were repeated
for the aspirin extracted by solvent extraction and pure aspirin. The solvent extracted aspirin
melted in the range of 136.2℃ to 156℃ while pure aspirin melted in the range of 136℃ to
140℃.
Discussion
The yield of aspirin is affected by different factors. Decomposition is one of the
factors which affect the yield of aspirin. Other factors include the purity of the chemicals
used and the conditions of the apparatus. If impure chemicals lead to low quality of aspirin
yield. Likewise dirty apparatus such test tubes results in low quality of aspirin yield.
According to the TLC analysis, pure aspirin was not synthesized in this experiment.
This indicates that both recrystallized aspirin and aspirin extracted by solvent extraction
contained acetylicsalic acid and salicylic acid. Recrystallized aspirin, aspirin extracted by
solvent extraction, and crude aspirin were impure.
In industries and laboratory techniques of aspirin, synthesis involve weighing, mixing
and drying of ingredients. In the laboratory, the main raw materials for aspirin synthesis are
2-hydroxybenzoic acid and ethanoic anhydride. In industries, the raw materials for aspirin
synthesis are the active ingredient and lubricants. In industries, there is compression of raw
materials which is lacking in the laboratory synthesis of aspirin.

SYNTHESIS OF ASPIRIN 6
Conclusions
According to the results of extracted solvent extraction and recrystallization, solvent
extraction and recrystallization techniques are not suitable for aspirin synthesis. Moreover,
TLC and other techniques such as calorimetry test should be incorporated when testing
aspirin purity.

SYNTHESIS OF ASPIRIN 7
References
Dobovisek, A., Fajmut, A., and Brumen, M., 2012. Strategy for NSAID administration to
aspirin-intolerant asthmatics in combination with PGE^sub 2^ analog: a theoretical
approach. Medical and Biological Engineering and Computing, 50(1), pp. 33-42.
Hans, H., Lone, A., Aksenov, V. and Rollo, C.D., 2015. Impacts of metformin and aspirin on
life history features and longevity of crickets: trade-offs versus cost-free life
extension? Age, 37(2), pp. 1-16.