Chapter 14 – Heinemann
Chemistry 2
From Organic Molecules to
Medicines
 One very useful application of organic reaction
pathways is in the design and synthesis of medicines.
 The main ingredients of medicines are drugs.
 A drug is any substance that alters a chemical process
in the body.
Aspirin
 Aspirin is widely used as a painkiller (analgesic)
and relieve inflammation and fever.
 It has its origins from a naturally occurring
substance called salicin.
 Salicin is converted to salicylic acid in the body
and this is the active substance that fights pain.
 Salicylic acid proved to be a more effective pain
killer than salicin but the acidic nature gave it an
unpleasant taste and caused mouth and stomach
irritations.
Aspirin
 It was found that the hydroxy group on the
salicyclic acid molecule will react with ethanoic
acid to form an ester called acetylsalicylic acid.
 The ester was much less irritating to the stomach
and was tasteless compared to taking salicylic acid
by itself.
 The ester is then hydrolysed in the alkaline
conditions in the small intestine and the salicylic
acid can take effect.
Organic Pathway to
Aspirin
 Acetylsalicylic acid can be formed by a direct
condensation reaction between salycylic acid and
ethanoic acid but the reaction is slow and the yield is
low.
 A more effective pathway is to form the ester from
salicylic acid and ethanoic anhydride.
Organic Pathway to
Aspirin
Hydrolysis of Aspirin
Penicillin
 Penicillin was discovered by accident when
scientist Alexander Fleming found a mould
growing on a petri dish containing a culture of
staphylococcus bacteria.
 He found that the mould was killing the outer
edges of the bacteria.
 A few years later, an Australian scientist named
Howard Florey improved processes to extract
larger amounts of penicillin from this mould and
used it for its antibiotic effects.
Penicillin
Figure 14.11 Fleming’s
culture plate. The mould
on the left (Penicillium
notatum) is overcoming
the growth of the smaller
staphylococci.
Penicillin
 As bacteria can reproduce every half an hour, it has the
ability to evolve much faster than humans. As such, it
is able to build up a resistance penicillin.
 To combat this, scientists synthesised different strains
of penicillin with different side chains.
 They also synthesised penicillin that could be taken
orally instead of being injetced.
Penicillin
Figure 14.12 The
molecular structures of
penicillins F, G, and V.
The structures were
worked out by Dorothy
Hodgkin (Figure 12.29),
who also worked out the
structures of insulin and
vitamin B12.
Penicillin
Figure 14.13
The structure of
6-aminopenicillanic acid.
Figure 14.14
Structure of oxacillin.
Greener Production of
Medicines
 When chemists first developed synthetic pathways for
making useful drugs, their main concern was to get a
good yield.
 Some methods contained a large amount of steps and
as such produced a large amount of waste products.
 This is referred to as poor atom economy.
Greener Production of
Medicines
 Over time, chemists have worked out greener reaction
pathways that are more efficient in terms of using
fewer steps in the synthesis, greater yields and better
atom utilization.
 This has made large savings both in dollar terms and
environmental impact.
Greener Production of Medicines