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Part 7.
The chemistry of
AROMATIC COMPOUNDS
Doc
Brown's Chemistry Advanced Level Pre-University Chemistry Revision Study
Notes for UK KS5 A/AS GCE IB advanced level organic chemistry students US
K12 grade 11 grade 12 organic chemistry
Part
7.13
Examples of aromatic compounds from the pharmaceutical industry and
examples of aromatic compounds found in natural
products
INDEX of AROMATIC CHEMISTRY
NOTES
All Advanced A Level Organic
Chemistry Notes
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Examples of synthetic
aromatic compounds from the pharmaceutical industry
Examples of analgesics -
pain-killers - anti-inflammatory drugs
Acetylsalicylic acid is one
chemical name for the brand
Aspirin.
N-(4-hydroxyphenyl)ethanamide is the IUPAC name for
the brand Paracetamol.
2-(4-(2-methylpropyl)phenyl)propanoic acid is the
IUPAC name for the brand Ibuprofen.
Phenol is manufactured from benzene by several different processes.
(The details not
required, but you should know the last three reactions in
the synthesis route.)
C6H6
== [O] ==> C6H5OH
Phenol is nitrated with nitric acid to give mainly 4-nitrophenol
(desired product) and some 2-nitrophenol.
C6H5OH
+ HNO3 ===> O2NC6H4OH
+ H2O
The 2-nitrophenol is removed
by steam distillation to leave mainly 4-nitrophenol.
Note the desired orientation
of the intermediates so that the final product's orientation is
correct.
The 4-nitrophenol is reduced with hydrogen (Ni catalyst ?) to
4-aminophenol.
O2NC6H4OH
+ 6[H] ===> H2NC6H4OH
+ 2H2O
4-aminophenol is ethanoylated with ethanoic anhydride to yield
N-(4-hydroxyphenyl)ethanamide aka 'Paracetamol'
H2NC6H4OH
+ (CH3CO)2O ===> CH3CONHC6H4OH
+ CH3COOH
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Examples of naturally occurring aromatic compounds -
the natural occurrence of the benzene ring!
Use of the term 'aromatic' derives from the smell of oil from natural
products - usually 'aromatic' plants.
Today the term refers to compounds containing a benzene ring, fused benzene
rings or other ringed compounds that chemically behave as an aromatic
compound.
Aromatic compounds from the natural world often have a strong pleasing smell
and are naturally found in wine, spices, perfumes, fragrance oils, and
essential oils extracted from plants.
 The
simplest aromatic aldehyde, benzaldehyde (right) smell's of almonds and is a
naturally occurring compound found in bitter almond oil. It is synthesised
by the chemical industry for use in food flavourings and fragrances in the
perfume industry.
Salicin (below) is a naturally found in the bark of willow
and poplar trees. For thousands of years it was known to have a pain-killing
action when ingested, it is an anti-inflammatory agent. The Salicin molecule
consists of a phenol attached by an ether linkage to hexose sugar molecule.
The search for molecules having a similar effect.
Salicylic acid (2-hydroxybenzoic acid) is derived from the metabolism of
Salicin and is used in medical treatment. However, synthetic acetylsalicylic
acid (Aspirin) was found to be a more effective painkiller. Soluble Aspirin
is absorbed more quickly minimising irritating the stomach.
The benzene ring even turns up opiates (a type of alkaloids)
such as naturally occurring morphine, codeine and heroin, but these are not
classed as aromatic compounds.
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INDEX of AROMATIC
CHEMISTRY NOTES
All
Advanced Organic Chemistry Notes
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