Stereochemistry Key Terms Flashcards
Superposable (or super imposable)
The ability to precisely overlap one object over another. Only identical objects are superposable, everything else is non-superposable
Stereocentre (chiral centre)
Atoms which bear groups such that the interchanging of two groups leads to a stereoisomer. (A carbon bonded to four distinct groups)
-other atoms can be stereogenic ie P, S and metallic ions bonded to ligands
Ligands
Ions or molecules bonded to a complex metal ion often by dative coordinate bonds
Chiral
(Handed) - not superposable on it’s mirror image
Achiral
Superposable on it’s mirror image
Meso-compound
Achiral AND contains two or more stereocentres
Enantiomers
Stereoisomers that are non-superposable mirror images
Diastereomers
Stereoisomers that are non-superposable, but are NOT mirror images. MUST contain two or more stereocentres
Isomers
Compounds that are non-superposable but have the same molecular formula. May be constitutional isomers or stereoisomers
Constitutional (or structural) isomers
Isomers which have the same molecular formula but different structural formulae
Stereoisomers
Isomers which have atoms that differ only by their orientation in space. Unlike constitutional isomers, they have equivalent structural formulae. May be geometric or optical
Racemic mixture
Solution containing equal proportions of both enantiomers so no optical activity (rotating polarised light)
Naming stereoisomers
- Face lightest atom away from you
- Point heaviest atom up
- Which of other two heavier? If same look at next atom attached to each etc (Cahn-Ingdd prelog rules)
- Number heaviest to lightest
- Anti-clockwise or clockwise?
S
Left handed (Sinister) Anti-clockwise
R
Right handed (Recto) Clockwise
