Cyclic saturated hydrocarbons: how they are produced. Cycloalkanes

In the article we will consider the preparation of cycloalkanes and the features of their structure. Let's try to explain the characteristic properties of these substances, based on the features of their structure.

Structure

First, let's analyze the structure of the named class of organic hydrocarbons. All cyclic compounds are divided into heterocyclic and carbocyclic species.

The second group has three carbon atoms inside the closed cycle. Heterocyclic compounds, in addition to carbon, also contain atoms of sulfur, oxygen, phosphorus, nitrogen in their molecules.

There is a division of carbocyclic compounds into aromatic and alicyclic substances.

Alicyclic substances

These include cycloalkanes. The chemical properties and the production of these substances are determined precisely by the closed nature of the structure of this class of hydrocarbons.

Alicyclic refers to those substances that have one or more non-aromatic cycles. The preparation and use of cycloalkanes is considered from the point of view of their relation to alicyclic compounds.

Classification

The simplest representative of this class of hydrocarbons is cyclopropane. In its structure there are only three carbon atoms. Representatives of this homologous series are called, in addition, paraffin. By their chemical and physical properties, they are similar to the ultimate hydrocarbons. The molecules contain single bonds formed by hybrid orbitals. In cycloalkanes, the type of hybridization is sp3.

The overall composition of the class is expressed by the formula CHH2n. These compounds are interclass isomers of ethylene hydrocarbons.

According to the modern international substitution nomenclature, when the representatives of this class are named, the prefix "cyclo" is added to the corresponding hydrocarbon in the number of atoms. In this case, for example, cyclohexane, cyclopentane is obtained. The rational nomenclature provides names for the number of closed methylene groups of CH2. Due to this, cyclopropane will be called trimethylene, and cyclobutane - tetramethylene.

For this class of organic substances is characterized by structural isomerism, relating to the number of carbon atoms in the cycle, as well as optical isomerism.

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Now consider how the receipt occurs. Cycloalkanes can be obtained in several ways, depending on which starting material is chosen for chemical conversion. We will analyze the main variants of paraffin synthesis.

So, what is their receipt? Cycloalkanes are formed by cyclizing the dihalogen derivatives of the ultimate hydrocarbons. By a similar chemical method, four- and three-membered rings are formed. For example, cyclopropane. Let us consider in more detail its preparation: cycloalkanes, which are the first representatives of a given homologous series, are formed by the action of metallic magnesium or zinc on the dihalogen derivative of the corresponding alkane.

And how can we form five-membered and six-membered cyclic compounds, how are they obtained? Cycloalkanes with such an amount of carbon atoms in the structure are difficult to create, because due to conformation there will be a problem with the cyclization of the molecule. This phenomenon is explained by the free rotation of the C-C bond, which substantially reduces the probability of obtaining a cyclic compound. To form these representatives of cycloalkanes, the starting materials are the 1,2- or 1,3-dihalogen derivatives of the corresponding alkane.

Among the methods of paraffin synthesis, we also distinguish the process of decarboxylation of dicarboxylic acids and salts. Five- and six-membered cycloalkanes are obtained by intermolecular condensation.

And among the special methods for their formation, we note the reaction between alkenes and carbenes, the reduction of oxygen-containing derivatives of cyclo-compounds.

Chemical properties

All possible ways of obtaining cycloalkanes and their interaction are determined by the features of the chemical structure. Given the presence of a cyclic structure, among the basic chemical properties of cycloalkanes, we distinguish the reactions of hydrogen addition (hydrogenation), its elimination (dehydrogenation).

To carry out the reactions, a catalyst is used, in the role of which platinum, palladium can act. Interaction is carried out at elevated temperature, its magnitude depends on the size of the cycle. When a cyclic hydrocarbon molecule is exposed to UV radiation, it is possible to carry out a chlorination reaction (addition of chlorine).

Like all representatives of organic compounds, cycloalkane is able to enter a combustion reaction, forming after interaction carbon dioxide, water vapor. This reaction refers to exothermic processes, since it is accompanied by the release of a sufficient amount of heat.

Conclusion

Paraffins are closed hydrocarbon compounds formed from dihalogenated derivatives of alkanes or other organic compounds. The features of their structure determine the basic chemical properties of cycloalkanes, the field of their application. They are mainly used in organic synthesis to produce oxygen-containing organic substances.