Organic Chemistry: Stereo Chemistry

Section 1: Introduction to Stereochemistry

Stereochemistry relates to the spatial arrangement of atoms in a molecule and how these arrangements influence the chemical behaviour of the organic compounds.
In stereochemistry, the same atoms connected in the same sequence can exist in various forms due to different spatial arrangements, these distinct forms are called stereoisomers.
Stereochemistry has two major subtypes: geometrical isomerism (also called cis-trans isomerism) and optical isomerism.

Section 2: Geometrical Isomerism

Geometrical isomerism occurs in organic compounds which contain a carbon-carbon double bond (C=C), due to the restricted rotation around the double bond.
For cis-isomers, similar or identical groups are on the same side of the double bond. For trans-isomers, similar or identical groups are on opposite sides of the double bond.
Cis and trans isomers show different physical and chemical properties, most importantly, their boiling points, polarity, and reactivity differ.

Section 3: Optical Isomerism

Optical isomerism occurs in molecules containing a chiral carbon atom, which is a carbon atom with four different atoms or groups attached.
Optical isomers, also known as enantiomers, are mirror images of each other, just like left and right hands. They exhibit the same physical and chemical properties except in their interaction with plane polarised light.
They contain a center of asymmetry, a chiral center or chiral carbon, which allows for this mirror imaging behaviour.
One form will rotate plane polarized light to the right (dextrorotatory), and the other will rotate the light to the left (levorotatory).

Section 4: Importance of Stereochemistry in Organic Chemistry

Understanding stereochemistry is crucial in predicting how molecules will react in chemical reactions.
The different reactivities of stereoisomers can drastically influence the outcome of reactions.
This has critical implications in the pharmaceutical industry, as different forms can have different or even opposite bioactivity. The most well-known example being Thalidomide, where one form was beneficial and the other harmful.
As such, understanding stereochemistry allows for the precise design and manufacture of therapeutic agents.