OIA1012 STEREROCHEM

HI

What is stereoisomerism? 

Compounds with the same molecular formula but different spatial arrangements of atoms.

Name three types of stereoisomerism. 

Geometrical, conformational, and optical isomerism.

Define geometrical isomerism. 

Isomerism due to restricted rotation around double bonds or ring systems.

Example of geometrical isomerism? 

Cis(Z)-2-butene and trans(E)-2-butene.

What is the Cahn-Ingold-Prelog rule? 

A system to assign priorities to substituents based on atomic numbers.

Define conformational isomerism. 

Isomers formed by rotation around single bonds, e.g., staggered and eclipsed forms.

What is the most stable conformation of ethane? 

Staggered conformation, due to minimized non-bonded interactions

What is chirality? 

A property where a molecule is non-superimposable on its mirror image.

Define enantiomers. 

Pair of chiral molecules that are mirror images of each other.

What is a racemic mixture? 

A 1:1 mixture of two enantiomers that does not rotate plane-polarized light.

What are diastereomers? 

Stereoisomers that are not mirror images of each other.

What is a meso compound? 

A molecule with multiple chiral centers that is optically inactive due to internal symmetry.

Why are enantiomers important in pharmacology? 

They can have different biological activities, e.g., (-)-Adrenaline is 15x more active than (+)-Adrenaline.

Name methods of chiral recognition. 

Polarimetry, chromatography, and circular dichroism spectroscopy.

How many stereoisomers are possible for a molecule with 3 chiral centers? 

(2^n = 2^3 = 8) stereoisomers.