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Chapter 7 : Stereochemistry |
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Implications in Reactions
- In general terms it is easier
to destroy the optical purity of a pure enantiomer than to make an optically
pure enantiomer.
- In the absence of other chiral
molecules, reactions will generate achiral products or racemic mixtures.
To appreciate this, think of your hands
or feet. They interact with achiral objects without any difference in comfort
between the two, but with a chiral object, they feel different..... can't you
tell when you have got your shoes on the wrong feet ?
As examples, carbocations and alkenes
which are both planar are attacked from either face in equal amounts generating
racemic product mixtures. This is because the faces of the systems are
equivalent and there is nothing to distinguish them.
- In order to create non-racemic
products, a chiral influence must be used. This could be in the starting material,
a reagent, a catalyst or even during purification.
Research into reactions or methods for
performing syntheses of single stereoisomers is very important due to requirement
to produce optically pure pharmaceutical products, especially where one enantiomer
is more effective than the other (remember your body is full of chiral amino acids,
enzymes and proteins...)
