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Meso Compound

What is Meso Compound?

An achiral compound with chiral centres is known as a meso compound. Although it has two or more stereocenters, a meso compound has an internal plane of symmetry that makes it superimposable on its mirror image and is optically inactive.

A meso compound is a stereoisomer with two or more chiral centres but no optical activity due to an internal plane of symmetry. Mesomers are compounds with zero net rotation of plane polarised light. In other words, mesomers are organic molecules that have two chiral carbons that are identical, resulting in zero net rotation.

Table of Contents

Meso Compound Definition

Meso compounds feature several chiral centres and are achiral substances. Despite having stereocenters, it is overlaid on its mirror counterpart and is optically inactive.

An achiral compound with chiral centres is known as a meso compound. Although it has two or more stereocenters, a meso compound has an internal plane of symmetry that makes it superimposable on its mirror image and is optically inactive.

A non-optically active member of a group of stereoisomers, at least two of which are optically active, is known as a meso compound or meso isomer. This signifies that the molecule is not chiral, despite the presence of two or more stereogenic centres.

Meso Compound Examples

Meso compounds feature chiral centres (sp3 hybridised tetrahedral atoms bound to four distinct groups), yet they are achiral generally due to symmetry. As mentioned, a meso compound should include at least two chiral s p 3 hybridised atoms with the exception of the nitrogen atom of a tertiary amine and at least one internal plane that splits the molecule into two mirror copies.

The molecule cannot be planar because tetrahedral centres are involved. Any compound with even one symmetry element is achiral, which means it won’t rotate plane polarised light! As a result, meso compounds have no optical activity.

This molecule is achiral because it has a plane of symmetry (the horizontal plane passing through the red broken line); nonetheless, it has two chiral carbons and is thus a meso complex.

Meso Compound is Optically Active

A non-optically active member of a collection of stereoisomers, of which at least two are optically active, is known as a meso compound or meso isomer. This means that despite having two or more stereogenic centres, the molecule is not chiral. They’re achiral compounds, meaning they feature several chiral centres. It is overlaid on its mirror image and is optically inactive, despite having stereo centres.

It possesses an internal symmetry plane that splits the compound in two. These two sides are reflected in each other via the inner mirror. Stereochemistry in the stereocenter can be “cancelled out.” This indicates that if the molecule is divided into two symmetrical sides by an internal plane, the stereochemistry of the left and right sides should be opposite each other. As a result, the outcome is optically inactive. Theoretically, cyclic molecules are also meso. Because optical activity cancels out in the presence of a plane of symmetry, meso compounds do not display optical activity.

Frequently Asked Questions on Meso Compound

Why is meso achiral?

Meso compounds are achiral because they have a plane of symmetry and this will lead to a mirror image which is superimposable to the original molecule.

Are achiral compounds always meso?

A meso compound contains a plane of symmetry and so is achiral, regardless of whether the molecule has a chiral center. A plane of symmetry is a plane that cuts a molecule in half, yielding two halves that are mirror reflections of each other.

How do you know if a compound is optically active?

The compounds which are capable of optical rotation are said to be optically active compounds. All the chiral compounds are optically active. The chiral compound contains an asymmetric center where the carbon is attached with four different atoms or groups. It forms two non-superimposable mirror images.

What is meso compound in organic chemistry?

A Meso compound or meso isomer is a non-optically active member of a set of stereoisomers, at least two of which are optically active. This means that despite containing two or more stereogenic centers, the molecule is not chiral.

What is the meaning of meso form?

A form of an element that cannot demonstrate optical activity as a result of dextrogyrate and levogyrate effects that are balanced contrary to each other in a structure

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