MEDCHEM.01

Stereochemistry

The branch of chemistry concerned with the 3-dimensional artangement of atoms in molecules.

Isomers

compounds that have the same molecular formula but different arrangements of atoms or structures.

Stereoisomers

Isomers that have their atoms connected in the same order but have different 3-dimesional arrangements in space. It includes both enantiomers and diastereomers.

Enantiomers

Stereoisomers that are non-superimposable mirror images of each other. They have identical physical properties (ex. boiling point, density..). They have opposite configuration at all chiral centers.

Diastereomers

Stereoisomers that are not mirror images of each other and have different configurations at one or more chiral centers.

Optical Isomers

Another term for enantiomers, which exhibit optical activity and rotate plane-polarized light in opposite directions.

Conformational isomers

Stereoisomers that differ in the rotation around single bonds, leading to different spatial arrangements.

Configurational Isomers

Stereoisomers that cannot be interconverted by rotation around single bonds and require breaking and forming of bonds to change configuration.

Chirality

Chiral molecules are chemically identical to each other but possess unique three-dimensional shapes, making them mirror-images that are not superimposable on each other.Although chemically identical, chiral molecules may possess very different biologicalproperties

Chirality

A property of a molecule that makes it non-superimposable on its mirror image, resulting in two distinct forms known as enantiomers.

Achiral Molecules

Molecules that are superimposable on their mirror images, having no chiral centers.

Chiral Molecule Rules

1. Needs a stereogenic centre

   • A carbon atom with four different groups attached to it

2. Cannot have a plane of symmetry

Stereogenic centre

A carbon atom with four different groups attached to it

Enantiomers

A pair of molecules that are related as non-superimposable mirror images are called enantiomers.

Enantiomers physical properties

Enantiomers have identical physical properties such as melting point and boiling point, but differ in optical activity. They rotate plane-polarized light in opposite directions.

What is Plane-polarised Light?

Light that oscillates in a single plane, often used in optical experiments to study chiral substances.

How you can differentiate between a pair of enantiomers using a polarimeter

A polarimeter measures the angle of rotation of plane-polarized light caused by enantiomers, allowing for differentiation based on their opposite rotation directions.

Levorotatory

describes an enantiomer that rotates plane-polarized light to the left (counterclockwise).

Dextrorotatory

describes an enantiomer that rotates plane-polarized light to the right (clockwise).

How to calculate the specific rotation of a molecule

Specific rotation is calculated using the formula [α] = α / (c × l), where α is the observed rotation, c is the concentration in g/mL, and l is the path length in decimeters.

Racemic Mixture

a mixture containing equal amounts of both enantiomers, resulting in no net rotation of plane-polarized light, therefore optically inactive.

Optically active molecules

Can rotate the plane of polarised light.

Chirality in Drug Design

Chirality plays a critical role in drug design as chiral drugs may have different therapeutic effects; one enantiomer may be effective while the other could be harmful.

Chiral Amino Acids

Chiral amino acids are fundamental building blocks of proteins, creating a homochiral environment crucial for proper protein folding and functionality.

Enzyme Specificity

Enzymes are chiral and often exhibit specificity for one enantiomer over another, affecting binding affinity and reaction rates.