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The molecules in which chiral centers are present but the whole molecule is achiral are known as meso compounds. These molecules are achiral due to the presence of plane of symmetry and these types of compounds are superimposable and mirror images of each other. These compounds are optically inactive.

Meso compound

In this compound plane of symmetry is present. Therefore, this compound is meso compound.

Cyclic compounds having plane of symmetry will also be meso compounds. For example:

Meso compound

Reactant of the above reaction is an epoxy compound and its IUPAC name is 2, 3-Dimethyloxirane. In presence of acid i.e. we will get the product of reaction as shown below:

Meso compound

In the product of the reaction plane of symmetry is present therefore, it is a meso compound and as we know that meso compounds does not rotate the plane polarized light. Therefore, the product of this reaction will not rotate plane polarized light.