25.3- SYNTHESIS OF OPTICALLY ACTIVE COMPOUNDS Flashcards
What is a racemic mixture or racemate?
50-50 mixture of two optical isomers
Is a racemate optically active?
no
Why is a racemate not optically active?
as effects of the two isomers cancel out
Are all naturally occurring amino acids chiral?
yes
Although all naturally occurring amino acids are chiral, how are they formed in nature?
only one of the isomers formed in nature
Why are only one of the isomers of amino acids formed in nature?
as most naturally occurring molecules made using enzyme catalysts, which only produce one of possible optical isomers
How do many drugs work by?
work by molecule on active ingredient fitting on area of cell (called receptor) or enzyme’s active site
Why can only one of a pair of optical isomers fit a receptor? (drugs)
as receptors have three-dimensional structure
In some cases, one optical isomer is an effective drug and the other is inactive, what are the three options?
separate the two isomers- may be difficult + expensive as optical isomers have very similar properties
sell mixture as drug- wasteful as half of it is inactive
design an alternative synthesis of drug that makes only required isomer
Example of drug which is sold as racemate?
ibuprofen- over-the-counter painkiller + anti-inflammatory drug
In some cases, what can each of the optical isomers be like in a drug?
one effective drug and other toxic or has unacceptable side effects
Examples of drug where one isomer is effective drug and other has unacceptable side effects?
naproxen
one used to treat arthritic pain, whilst other causes liver poisoning
