Isomerism is a rather important characteristicchemical substances, since its properties depend on the structure and orientation of the molecule. The types of isomerism, as well as the peculiarity 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 considered 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 inscience is not so long ago. Several centuries ago it was noticed that some substances with the same parameters of molecular weight and the same set of atoms differ in their properties.
As an example, grape andtartaric acid. In addition, at the beginning of the nineteenth century a discussion ensued between the scientists Yu. Liebich and F. Wehler. In the course of numerous experiments, it was determined that there are two varieties of AgCNO-agglomerate and cyanic 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 J. Vant-Hoff, the phenomena of spatial and structural isomerism were explained.
Isomerization is a specific reaction, inthe time of which the transformation of structural isomers into one another is observed. As an example, you can take substances from a number of alkanes. Structural types of alkane isomerism make it possible to convert certain substances into isoalkanes. Thus, in industry, the octane number of fuel increases. It is worth mentioning that such properties are of great importance for the development of industry.
Types of isomerism are divided into two large groups.
Structural isomerism and its varieties
Structural isomerism is a phenomenon in which isomers differ among themselves by chemical structure. There are several separate species
1. Isomerism of the carbon skeleton. This form is characteristic of carbons and is associated with different order of bonds between carbon atoms.
2. Isomerism by the position of a functional group.This phenomenon is associated with a different position of the functional group or groups in the molecule. Examples include 4-chlorobutane and 2-chlorobutanoic acid.
3. Isomerism of multiple bonds. Incidentally, the most common types of alkenes isomerism can be included here. The isomers differ in the position of the unsaturated bond.
4. Isomerism of the functional group.In this case, the total composition of the substance is preserved, but the properties and character of the functional group itself change. Examples include dimethyl ether and ethanol.
Spatial species of isomerism
Stereoisomerism (spatial) is associated with a different orientation of molecules of the same structure.
1. Optical isomerism (enantiomerism).This form is associated with the rotation of functional groups around the asymmetric bond. In most cases, the substance has an asymmetric carbon atom, which is linked to four substituents. Thus, the plane of polarization of light rotates. As a result, so-called mirror antipodes and isomers are formed. It is interesting that the latter are characterized by almost identical properties.
2. Diastereometry. This term denotes such a spatial isomerism, as a result of which antipodes are not formed.
It should be noted that the presence of possible isomers is primarily related to the number of carbon bonds. The longer the carbon skeleton, the more isomers it can form.
