Download WM5 The synthesis of salicylic acid and aspirin

WM5 The synthesis of salicylic
acid and aspirin
Synthesis is better than harvesting
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Chemists can synthesise (artificially produce)
compounds once the structure is known;
Phenol’s germicidal properties were well
known by the end of 19th Century;
Phenol (a product from heating coal) was
readily available;
2-hydroxybenzoic acid has 1 extra functional
group compared to phenol;
How is phenol converted into 2hydroxybenzoic acid?
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Draw the structures of phenol and 2hydroxybenzoic acid;
What extra atoms need to be added to
phenol?
What conditions and reagents are needed?
(research this);
Kolbe –Schmitt synthesis
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Kolbe (1874) produced
salicylic acid from dry
sodium phenoxide in a
stream of carbon dioxide
at 150 – 160 °C. He found
that the yield was only
50%.
Schmitt (1884) increased the yield to 90% by
increasing the pressure to 5 bar (7atm) until no more
CO2 was taken up.
On an industrial scale…
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Felix Hoffmann developed the process for
the Bayer company;
Unpleasant side-effects on mouth, gullet and
stomach;
Hoffmann modified the structure and tested
products on his rheumatic father!
1898: 2-ethanoylhydroxybenzoic acid (a.k.a
acetylsalicylic acid or aspirin) produced
Aspirin: made by esterification
You can read about esters and
esterification in CI 13.4.
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Aspirin is an ester O
Functional group R-C-O-R’
Alcohol + acid  ester
Aspirin is not very soluble in water so it
became the first medicine to be sold as
tablets;