Chapter 11A - Chirality & Optical Isomers

Molecule w/ a superimposable mirror image

Carbon atom in a compound attached to four unique chemical environments

Two non-superimposable mirror images of the same compound

An approximate 50/50 mixture of a chiral compound’s two optical isomers, which does not rotate polarised light in a specific direction

Compounds having the same molecular formula, with atoms arranged in the same order, but these atoms have different spatial arrangements.

• able to rotate plane of polarised light in opposite directions • one enantiomer would rotate plane of polarised light clockwise vice versa.

• contain at least one chiral centre (chiral carbon) • all molecules w/ one chiral centre are chiral • multiple chiral centres + plane of symmetry = achiral • multiple chiral centres + no symmetry plane = chiral

• impacts compound effectiveness • one optical isomer may have medicinal properties • other may have no or an adverse effect • interact differently b/c medicinal molecules have specific 3D shape & electrostatic interactions to bind w/ desired receptors

• must select/isolate a specific optical isomer to ensure medicine acts as intended • racemic mixture is produced where the specific optical isomer (w/ medicinal benefits needs to be isolated from the racemate) • under biological conditions, some medicines re-reacemise & does not guarentee safety/efficiency of final product

• polarised light • mixture will not rotate polarised light in specific direction • individual isomers will rotate polarised light in specific direction • seperation not always possible & common failure for potential medicines