Optical Isomerism Flashcards
what is an optical isomer (enantiomers)
a pair of non-superimposable mirror images
found in organic molecules that contain a chiral centre
what is a chiral centre
a chiral centre (carbon) is a carbon atom with four different groups attached
(indicated by an asterik)
what has each chiral centre got
a pair of optical isomers/ enantiomers
what are the 2 ways enantiomers can be synthesised
1. Natural Synthesis - molecules produced naturally by enzymes, will only be present as a single optical isomer
2. Synthetic Laboratory Synthesis - molecules prepared synthetically in the laboratory often contain a mixture of both optical isomers, usually leading to a racemic mixture
what is a racemic mixture
equal 50/50 mixture of entaniomers
what is plane-polarised light
when light waves vibrate in only one direction
why are enantiomers optically active
they can rotate the plane of polarised light - one enantiomer rotates it one direction and the other enantiomer rotates it by the same amount in the opposite direction
why are racemates optically inactive
they have no effect on the plane of the light
how do you distinguish between 2 enantiomers
- dissolve enantiomer in solution
- shine plane polarised light on the sample
- observe the degree of rotation
explain why a racemic mixture is produced
- carbonyl group is planar
- equal chance of attack from CN-
- from either side
