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Diene hydrocarbons: structure, isomerism and nomenclature

Diene hydrocarbons (diolefins, alkadienes, dienes) are saturated hydrocarbons, in the structure of which there are two double bonds. Given the chemical structure, the alkadienes are divided into three types: type I - diolefins with cumulated bonds (CH2CCH2); II type - alkadienes with conjugated (conjugated) bonds; Double bonds in the structure of the diene are separated by a single bond (H2SOCH2CH2); III type - dienes with isolated bonds (H2CH2CH2CHCH2).

Diene hydrocarbons: general characteristics

Of the three types of dienes, the most interesting for the chemical industry are type II alkadienes. With the help of electron diffraction it was established that the double bonds in the butadiene molecule between C1 and C4 are longer than in the ethylene molecule.

Diene hydrocarbons: isomerism

For these organic compounds, there are two types of isomerism - spatial (stereoisomerism) and structural. The first is the isomerism of the structure of the hydrocarbon chain, which can be straight or branched. The second type of isomerism is due to the spatial localization of atoms and atomic groups near the double bonds. Thus, trans- and cis-isomers of dienes are formed. For example, for a diene with the molecular formula C5H8 there are three structural isomers:

CH2CH2CH2CH2CH2; CH2C (CH3) CHCH2; CH3CH2CH2CH2.

Diene hydrocarbons: nomenclature

For the name of dienes two nomenclatures are used - historical (for example, divines, alen) and IUPAC (International Union of Theoretical and Applied Chemistry). According to the IUPAC nomenclature, the corresponding diene alkane is first named, in the name of which the suffix "en" is replaced by "diene", then the digits indicate the location of the double bonds in the hydrocarbon chain. The numbering of the hydrocarbon chain is carried out so that the numbers have the smallest value. The above diene formulas for the IUPAC nomenclature will be referred to as: 1,4-pentadiene; 2-methyl-1,3-butadiene; 1,3-pentadiene.

There are a number of industrial and laboratory methods for the synthesis of dienes. The main ones are the depolymerization of natural rubber (dry distillation), the method of catalytic dehydration of alkanes, the method of dehydration of monohydric saturated alcohols.

Butadiene is a valuable raw material for the production of synthetic rubbers (butadiene-nitrile, butadiene, styrene), as well as perchlorovinyl. Isoprene is a substance with a characteristic odor. For the first time, isoprene was obtained from natural rubber by the method of dry distillation. Isoprene is also produced by dehydration of isopentane. They are used for the production of synthetic rubbers, medicinal and aromatic substances.

Rubbers are an elastic and very strong material of organic origin, which is obtained from natural raw materials (natural rubber) and synthetic methods (synthetic). The basis of rubber are diene molecules with conjugated double bonds. In the process of processing this material of sulfur and heating (vulcanization), rubber is formed. Rubbers are a very important raw material for the production of tires and chambers, insulating strips, rubber mittens, shoes and other items used in industry, economy, life, medicine and veterinary medicine.

Ethylene hydrocarbons in their structure have one double bond. Sometimes these compounds are called olefins, since lower gaseous alkenes, reacting with chlorine or bromine, form oily compounds that are insoluble in water.

Acetylene hydrocarbons (alkynes) are compounds that contain one triple bond. The highest value of all alkynes is acetylene, which is obtained by the interaction of calcium carbide with water. This gas is used for autogenous welding and cutting of metals. Acetylene is a valuable raw material for the production of ethylene, ethyl alcohol, acetaldehyde, vinylacetylene, acetate, benzene, trichloroethane, acrylonitrile.

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