What is chiral center or stereogenic center?
The isomerism in which two or more compounds have same physical and chemical properties but they have different behavior towards plane polarized light, are known as optical isomerism and such type of compounds are known as optically active compounds.
When a single tetrahedral atom is attached with four different groups or atoms, then traditionally such atoms have been called chiral centers or stereogenic atoms or asymmetric atoms or stereo centers.
For example, the tetrahedral carbon atom of 2-butanol that attached with four different groups is an example of chiral center. Chiral centers are often designated by an asterisk (*) sign.
What is chirality?
Chirality is a phenomenon that pervades the universe and by which we can know about chiral or achiral (not chiral) properties of a particular object.
We can tell, if an object has chirality or not by examining the object and its mirror image. Every object has a mirror image.
Now, if the object and its mirror image are identical, that is, the object and its mirror image are superposable one on the other, then the object is said to be achiral or not chiral.
On the other hand, if the object and its mirror image are not identical, that is, the object and its mirror image are not superposable one on the other, then the object is said to be chiral.
In other word, a chiral object is one that can’t be superposed on its mirror image. For example, lactic acid is not superposable on its mirror image, is said to possess chirality.
What Is Chiral Or Asymmetric Molecule?
The term chirality has been used to describe such molecules which have no element of symmetry, that is, plane of symmetry, center of symmetry or alternating axis of symmetry.
Therefore, asymmetric molecules, that is, molecules with chiral centers are called chiral molecules. For examples, 2-butanol, 2-bromo butane etc.
What is plane polarized light?
Generally light is considered as electromagnetic wave of different frequency. The light obtained from any source vibrates in all direction and it is known as non polarized light.
But when this light is passed through a nickel prism it will absorb all abnormal radiation and light emerged from it is known as plane polarized light because in it all particles will vibrate in a given direction or plane.