What are isomers?


In the field of chemistry you can find many important branches that study compounds and substances. Among these branches we find organic chemistry , a science that is in charge of studying the different structures, properties and reactivation of compounds, mainly those that are made up of carbon and hydrogen. This phenomenon is known by the name of isomerism and the substances that are part of it are known by the name of isomers .

What are isomers?

Isomers are a type of chemical molecule that has the same molecular structure but at the same time has a different arrangement in the atoms that are located in space.

  • Definition
  • Characteristics of isomers
  • History
  • Types of isomers
  • Physical and chemical properties
  • What are they for
  • Importance
  • Examples of isomers


Isomers are substances that are part of a chemical compound that, despite having an identical molecular formula , have a great variety of differences in terms of structure or spatial configuration , in addition, they may also present differences in their chemical and physical properties.

Characteristics of isomers

The main characteristics of the isomers are the following:

  • They have the same chemical formula and the same molar mass .
  • They have the ability to be molecularly grouped in different ways.
  • Their chemical and physical properties also have important differences.
  • They have the same number and type of atoms in their structure.
  • They can be related to each other by means of structural and three-dimensional formulas .


The history of isomers goes hand in hand with isomerism and it arose during the first half of the 19th century when scientists realized and were able to demonstrate that chemical substances had properties that did not depend entirely and solely on their composition , but also the arrangement of the atoms within the molecule was important .

The first isomers that could be identified by chemists and scientists were silver fulminate and silver cyanate . The chemists were in charge of sending the work and reports to a scientific journal, which was directed by Gay-Lussac . When they were studied, it was possible to determine that the formulas that the molecules had was exactly the same (AgCNO) but at the same time they noticed that the form in which the atoms were found was different.

In 1828 , one of the most important events in the history of organic chemistry happened when Wöhler succeeded in synthesizing urea and with this he proved that organic compounds could be properly synthesized within a laboratory. In the year 1830 , Berzelius managed to observe that, when tartaric acid was obtained , two different forms with the same composition could be produced and it was in this way that a definition of isomerism was formulated for the first time in the world .

Types of isomers

There are several types of isomers and they can be qualified in two different ways, which are explained below.


This type of isomer differ in the way they manage to maintain and bind the atoms and three different types.

  • Of position : they are the isomers that are present in the substances in which the structure is different only by the functional group of the carbon skeleton.
  • Chain : can be found in substances that have a structural formula that differs from carbon atoms.
  • Function : in this group are those substances that have the same molecular formula but at the same time have a different functional group.


This type of isomer has a molecular formula equal to the grid , they have an identical sequence of bonded atoms, including the bonds of the atoms, however, they are different in terms of their three – dimensional orientation in space. There are several different types of them.

  • Geometric : they do not present the free rotation of the axis of the bond and it is the type of isomer that is commonly found in carbon double bonds but none of these bonds have the same substituents. Geometric isomers can have a cis form (when the carbon atoms are in the same region of space) and a trans form (when the atoms are in different regions of space).
  • Configurational isomers : this type of isomer has a reference molecule which has an opposite configuration in a ester center, in other words only undergoing the breaking of covalent bonds.
  • Enantiomers : arise when the mirror image of one of the compounds can be superimposed on that of the other. They have the same physical and chemical properties but differ in their interaction with other chiral molecules.
  • Diasteroisomer : They are different in their physical and chemical properties.

Physical and chemical properties

Among the physical and chemical properties of isomers, the following are mentioned:

  • One of their properties is that they have relative proportions of atoms , which make up the molecule.
  • They have molecular structures
  • They have the same molecular formula .
  • They have two or more compounds that have the same molecular formula.
  • They are distributed differently.
  • The points of boiling and melting of the compounds are different.
  • They cannot be superimposed on each other.
  • They have the same number of atoms .

What are they for

One of the possible uses for isomers is to find and display the different types of chemodynamic behaviors and the possible toxicities that can be found in the chemistry of air pollution . They also serve to create medicines , which currently have a greater and better range of safety and effectiveness.


The main importance of isomers lies mainly in the field of clinical pharmacology or pharmacotherapy since these types of compounds are different in terms of their pharmacokinetic and dynamic properties , which gives them a series of important benefits. Isomers have helped evolve the creation of new drugs and produce drugs that are safer for human consumption while also being more effective.

Examples of isomers

Some examples of isomers are as follows:

  • Ethyl alcohol
  • Dimethyl ether
  • Butane
  • Isobutane

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