Identical Compounds

When two compounds are same and cannot be distinguished, they are said to be identical. Isomers are molecules or polyatomic ions that have the same molecular formulas — that is, the same number of atoms of each element — but different atomic configurations in space. The existence or the potential of the isomers is referred to as isomerism.

The chemical and physical properties of the  isomers need not to be the same. The two primary types of isomerism are structural or constitutional isomerism, in which the bonds between the atoms differ, and stereoisomerism or spatial isomerism, in which the bonds remain same except the relative positions of the atoms differs.

A hierarchy of isomeric relationships exists. When two compounds are investigated further, they may have the same constitutional isomer yet are stereoisomers of each other. Two molecules with the same stereoisomer but different conformational forms or isotopologues may have different conformational forms or isotopologues.

Structural isomerism

Structural (constitutional) isomers have the same chemical formula but differ in their atom bonding arrangements. Stereoisomers contain molecular formulae and atom configurations that are identical. Only the spatial orientation of groups in the molecule distinguishes them. There are various types of stereoisomers in organic chemistry: enantiomers, diastereomers, geometric isomers, and conformers. Several chapters will be dedicated to introducing and explaining stereoisomers.

Isomers with structural (constitutional) properties

Because carbon creates four bonds, the octet rule can be used to create a variety of compounds. Even with only four carbon atoms, the carbon backbone can have two different forms. Carbon atoms can be linked together to form a four-carbon chain (butane), or a one-carbon branch can be formed from a three-carbon chain (2-methylpropane). Because they both have the molecular formula C4H10, butane and 2-methylpropane are structural isomers.

Identical vs conformer

Dynamic molecules are created by the rotation of single bonds. It’s vital to remember that when sketching and discussing molecules, our drawings are static while the molecules themselves rotate. Although the ethane molecule has seven sigma bonds, rotation about the six carbon-hydrogen bonds has no effect on the molecule’s form because the hydrogen atoms are nearly spherical. Rotation around the carbon-carbon bond, on the other hand, results in a wide range of molecular conformations. Stereoisomerism is best illustrated by conformers.

Geometric isomerism can be created by the stiffness of the pi bonds in double bonds. There are two potential orientations across the carbon-carbon double bond (C=C) without rotation. The double bond’s stiffness serves as a point of reference for spatial orientation. Geometric isomers are distinguished by the prefixes cis and trans. Both non-hydrogen atoms are on the same side of the double bond in the cis-stereoisomer. The non-hydrogen atoms are across the double bond in the trans-stereoisomer.geometric isomerism can be created by the stiffness of the pi bonds in double bonds. There are two potential orientations across the carbon-carbon double bond (c=c) without rotation. The double bond’s stiffness serves as a point of reference for spatial orientation. Geometric isomers are distinguished by the prefixes cis and trans. Both non-hydrogen atoms are on the same side of the double bond in the cis-stereoisomer. The non-hydrogen atoms are across the double bond in the trans-stereoisomer.

Identical vs enantiomers

Identical compounds are those in which all of the atoms are arranged in the same spatial orientation. Conformers are the same chemical, but rotated around single bonds in different ways.

In chemistry, enantiomer refers to mirror images of molecules that cannot be combined to form a single molecule. Identical, on the other hand, refers to traits that are comparable.

In an achiral environment, both enantiomers have the same chemical and physical properties. Enantiomers interact with other chiral compounds differently by rotating the direction of plane polarized light to equal but opposite angles. In an achiral environment, both enantiomers have the same chemical and physical properties.

Conclusion 

Identical compounds are such types of compounds in which all of the atoms are arranged in the identical spatial orientation.

Conformers are the same chemical, but rotated around single bonds in different ways. Enantiomers are non-identical molecules that are non-superimposable mirror images of each other and contain at least one chiral carbon or chiral centre, hence forming chiral compounds. Except when they interact with other chiral molecules, they exhibit chemical properties that are very similar. When plane polarised light passes through distinct stereoisomers, it rotates in different directions (from a pair of enantiomers). A polarimeter determines which enantiomers are present by measuring the amount of rotation of this plane polarised light.