Isomerism is a rather important characteristic of chemicals, since its properties depend on the structure and orientation of the molecule. Types of isomerism, as well as a feature of the structure of substances are actively studied to this day.
Isomerism and isomerization: what is it?
Before considering the main types of isomerism, it is necessary to find out what this term means. It is generally accepted that isomerism is a phenomenon when chemical compounds (or isomers) differ in the structure and arrangement of atoms, but at the same time are characterized by the same composition and molecular weight.
In fact, the term "isomerization" appeared in science not so long ago. Several centuries ago, it was noticed that some substances with the same molecular mass and the same set of atoms differ in their properties.
An example is grape and tartaric acid. In addition, at the beginning of the nineteenth century, a discussion ensued between scientists J. Liebig and F. Weller. In the course of numerous experiments, it was determined that there are two varieties of a substance with the AgCNO formula - explosive and cyanate silver, which, despite the same composition, have different properties. Already in 1830, the concept of isomerization was introduced into science.
Later, thanks to the work of A. Butlerov and Y. Vant-Hoff, the phenomena of spatial and structural isomerism were explained.
Isomerization is a specific reaction during which the conversion of structural isomers into each other is observed. As an example, you can take substances from a number of alkanes. Structural types of isomers of alkanes make it possible to convert certain substances into isoalkanes. Thus, in industry, the octane number of fuel rises. It is worth mentioning that such properties are of great importance for the development of industry.
Types of isomerism is usually divided into two large groups.
Structural isomerism and its variants
Structural isomerism is a phenomenon in which isomers differ in chemical structure. Several distinct species are distinguished here.
1. Isomerism of the carbon skeleton. This form is characteristic of carbons and is associated with a different order of bonds between carbon atoms.
2. Isomerism by the position of the functional group. This phenomenon is associated with different positions of the functional group or groups in the molecule. As an example, 4-chlorobutanoic and 2-chlorobutanoic acid can be given.
3. Isomerism of multiple bonds. By the way, this includes the most common types of isomers of alkenes. Isomers differ in the position of the unsaturated bond.
4. Isomerism of the functional group. In this case, the general composition of the substance is preserved, but the properties and nature of the functional group itself change. Examples include dimethyl ether and ethanol.
Spatial Views of Isomerism
Stereoisomerism (spatial) is associated with different orientations of molecules of the same structure.
1. Optical isomerism (enantiomerism). This form is associated with the rotation of functional groups around an asymmetric connection. In most cases, the substance has an asymmetric carbon atom, which is associated with four substituents. Thus, the rotation of the plane of polarization of light occurs . As a result, the so-called mirror antipodes and isomers are formed. Interestingly, the latter are characterized by almost the same properties.
2. Diastereomerism. This term refers to such a spatial isomerism, as a result of which antipodes are not formed.
It is worth noting that the presence of possible isomers is primarily associated with the number of carbon bonds. The longer the carbon skeleton, the greater the number of isomers can form.