Question

What does meso mean in organic chemistry?

Answer 1

Hint: Let us first get some ideas about organic chemistry. Organic chemistry is a branch of chemistry that studies the structure, properties, and reactions of organic compounds with covalent bonds between carbon atoms. The chemical composition and formula of a substance are determined by studying its structure.

Complete answer:
Meso compounds have several chiral centres and are achiral compounds. Despite its stereocenters, it is optically inactive since it is superimposed on its mirror image.A meso compound should have two or more equivalent substituted stereocenters in general. In addition, the compound is divided in half by an internal symmetry plane. The internal mirror reflects the two halves back at each other. Stereocenters' stereochemistry can "cancel out." What this implies is that when a compound is divided into two symmetrical sides by an internal plane, the stereochemistry of the left and right sides should be opposite, resulting in optically inactive results. It's possible that cyclic compounds are also meso.
Let’s see how we can identify meso.
If A is a meso compound, it must have at least two stereocenters, an internal plane, and R and S stereochemistry.
Look for an internal plane, also known as an internal mirror, that runs through the compound.
The stereochemistry (e.g., R or S) is extremely important in deciding whether or not a compound is a meso compound. Since a meso compound is optically inactive, the stereochemistry of the two can balance out. In a meso compound with two stereocenters, for example, R cancels out S.

Note:
The substituted groups attached to a stereocenter can be rotated around to consider the internal plane, which is an interesting feature of single bonds or $s{p}^3$ -orbitals. The stereochemistry of the molecule does not shift when it rotates.