Thalidomide
Why is it important to understand isomerism?
Molecules that carry out specific functions exist as a one isomer only. This is because these
molecules are synthesised using enzymes. Enzymes are catalysts that can recognise other isomers as
different molecules. Other isomers will not fit onto the active sites used by the enzymes to catalyse
reactions and synthesise organic molecules. This is known as a lock and key method.
Pharmaceutical products acting on humans require the synthesis of single isomers. One isomer of a
commercially made pharmaceutical products may be more effective than the other. One isomer may
even be toxic to living systems.
The human body often requires the synthesis of single optical isomers. As well as the effectiveness of
the drug or chemicals. One isomer could be more effective than another, so it is administrated on its
own in lower doses. This is a less wasteful form of administrating and it causes fewer side effects.
The toxicity of these chemicals must be assessed also. This is because one isomer could be effective
while the mirrored isomer could be toxic. An example of this is the drug thalidomide. It is a chiral
compound and one optical isomer stops morning sickness in pregnant women, whilst the other
causes deformities in the foetus.
What is a racemic mixture?
This is defined as a mixture that is a 50/50 mixture of both optical isomers. There are equal amounts
of left and right-handed enantiomers of a chiral molecule. The synthesis of a racemic mixture is
cheaper than making a pure enantiomer. This is because it does not require special conditions.
(Master Organic Chemistry, 2019)
Thalidomide
Thalidomide was originally marketed as a mild sedative drug that was gave to women to treat
morning sickness. It was first developed in Germany and was marketed on the 1 st October 1957. It
was found to cause congenital malformation, especially of the limbs, in children whose mothers took
it during early pregnancy. It was withdrawn from use in the early 1960s due to the devastating
effects it caused by deforming thousands of babies and causing many infant fatalities. Over 10,000
children were born with thalidomide-related disabilities worldwide. Thalidomide led to tougher
testing and drug approval procedures in many countries, including the United States and the United
Kingdom. (Broughttolife.sciencemuseum.org.uk, 2019). One effect of thalidomide is targeting blood
vessels. It can block growth and tends to target parts of the body undergoing growth. Many other
forms of damage were caused to the children, including brain damage. Fortunately, many children's
disabilities were purely physical, and they could learn to cope with disabilities.
Thalidomide exists in two mirror-image forms. It is a racemic mixture of (R) - and (S)-enantiomers.
The (R)-enantiomer has sedative effects, whereas the (S)-isomer is teratogenic. Under biological
conditions, the isomers interconvert. (American Chemical Society, 2019)
Why is it important to understand isomerism?
Molecules that carry out specific functions exist as a one isomer only. This is because these
molecules are synthesised using enzymes. Enzymes are catalysts that can recognise other isomers as
different molecules. Other isomers will not fit onto the active sites used by the enzymes to catalyse
reactions and synthesise organic molecules. This is known as a lock and key method.
Pharmaceutical products acting on humans require the synthesis of single isomers. One isomer of a
commercially made pharmaceutical products may be more effective than the other. One isomer may
even be toxic to living systems.
The human body often requires the synthesis of single optical isomers. As well as the effectiveness of
the drug or chemicals. One isomer could be more effective than another, so it is administrated on its
own in lower doses. This is a less wasteful form of administrating and it causes fewer side effects.
The toxicity of these chemicals must be assessed also. This is because one isomer could be effective
while the mirrored isomer could be toxic. An example of this is the drug thalidomide. It is a chiral
compound and one optical isomer stops morning sickness in pregnant women, whilst the other
causes deformities in the foetus.
What is a racemic mixture?
This is defined as a mixture that is a 50/50 mixture of both optical isomers. There are equal amounts
of left and right-handed enantiomers of a chiral molecule. The synthesis of a racemic mixture is
cheaper than making a pure enantiomer. This is because it does not require special conditions.
(Master Organic Chemistry, 2019)
Thalidomide
Thalidomide was originally marketed as a mild sedative drug that was gave to women to treat
morning sickness. It was first developed in Germany and was marketed on the 1 st October 1957. It
was found to cause congenital malformation, especially of the limbs, in children whose mothers took
it during early pregnancy. It was withdrawn from use in the early 1960s due to the devastating
effects it caused by deforming thousands of babies and causing many infant fatalities. Over 10,000
children were born with thalidomide-related disabilities worldwide. Thalidomide led to tougher
testing and drug approval procedures in many countries, including the United States and the United
Kingdom. (Broughttolife.sciencemuseum.org.uk, 2019). One effect of thalidomide is targeting blood
vessels. It can block growth and tends to target parts of the body undergoing growth. Many other
forms of damage were caused to the children, including brain damage. Fortunately, many children's
disabilities were purely physical, and they could learn to cope with disabilities.
Thalidomide exists in two mirror-image forms. It is a racemic mixture of (R) - and (S)-enantiomers.
The (R)-enantiomer has sedative effects, whereas the (S)-isomer is teratogenic. Under biological
conditions, the isomers interconvert. (American Chemical Society, 2019)
