Optical Isomerism ORGANIC Flashcards
(17 cards)
What are stereoisomers?
Molecules that have same structural formula but atoms arranged differently in space
What are the two types of stereoisomerism?
Geometrical (E/Z)
Optical
What is a carbon atom known as when in a compound?
Chiral centre
How many bonds can carbon form?
4
What are enantiomers?
Optical isomers of compounds with chiral centre
How do enantiomers relate to each other?
Non-superimposable mirror images of each other
What is identical about enantiomers?
Physical and chemical properties
What is different about enantiomers?
Ability to rotate plane polarised light (one clockwise, the other anticlockwise)
How can identity of optical isomers of single substance be determined?
Depending on which isomer sample contains, plane of polarised light will be rotated either clockwise or anti-clockwise by fixed number of degrees
What needs to be determined to identify chiral centre?
Whether particular carbon is bonded to four different atoms or groups of atoms and so is chiral
Whether a particular carbon is bonded to two of same atoms or groups of atoms and so cannot be chiral
What are chiral centres marked with in drawings?
*
What three stereochemical drawing conventions are used when representing optical isomers?
Solid line is bond in same plane as paper
Dotted line is bond behind plane of paper
Solid wedge is bond in front plane of paper
What is a racemic mixture?
A mixture in which there are equal amounts of enantiomers present in solution
Are racemic mistures optically active?
Optically inactive
Enantiomers cancel out
Plane of polarised light will not change
What is meant by enantiopure?
A compound given by separation of enantiomers of racemic mixture
Why are many drugs given as racemic mixtures?
Separation process is expensive and time consuming
Not worthwhile even though only half of drug is pharmacologically active
What two reasons are there for only one enantiomer being produced for a drug?
Other enantiomer could be harmful
Drug expensive to synthesis so waste of materials and resources to produce 50% effective drug
