Question

What is meso isomers?

Answer 1

Hint : First we understand what is isomer: two or more compounds having the same molecular formula but different molecular structure/ arrangement of atoms in the molecules and the different properties.

Complete Step By Step Answer:
First, we understand some terms related to isomers like:
Chiral compound: carbon atom that is bonded to four different groups, and their mirror image cannot be superimposed.
Achiral compound: carbon atom that is not bonded to four different groups, and their mirror image can be superimposed. These are optically inactive (i.e., they cannot rotate plane polarized light).
Plane of symmetry(pos): virtual line which divides the compounds in symmetrical half, when there is a plane of symmetry present in a compound then the compound becomes optically inactive.
Meso isomers: An achiral compound with chiral centers is called meso compound.
Characteristics of meso compound:
-It has a plane of symmetry.
-It has at least two chiral carbons.
-It Can be superimposed on the mirror object (by $180$ degrees).
-It can demonstrate the mirror plane of symmetry.
-Molecule is achiral.
-Molecule is optically inactive.

Note :
You can easily identify that the compound is meso compound/isomer or not by checking some two points like : The compound chiral or not(by checking that all the four atoms attached must be different) and by checking the plane of symmetry (which divides the compound exactly in two symmetrical parts).
When both conditions get satisfied which proves that the compound is meso compound or meso isomer.