dienes (diolefins alkadienes, dienes) - saturated hydrocarbons, in the structure where there are two double bonds.Considering the chemical structure alkadienes are divided into three types: Type I - diolefins cumulated bonds (SN2SSN2);Type II - alkadienes with conjugations (conjugated) bonds;double bonds in the diene structure are separated by a single bond (N2SSNSNSN2);Type III - dienes with insulated connections (N2SSN2SN2SNSN2).
diene hydrocarbons: general characteristics
Of the three types of dienes of greatest interest to the chemical industry are alkadienes type II.Using electron found that the double bonds in the molecule butadiene between C1 and C4 are longer than in the molecule ethylene.
diene hydrocarbons: isomerism
For these organic compounds characterized by two types of isomerism - space (stereoisomerism) and structural.The first kind - isomerism structure a hydrocarbon chain which may be straight or branched.The second type of isomerism is due to spatial localization of atoms and atomic groups around double bonds.Thus, the image of trans and cis isomers dienes.For example, a diene with the molecular formula S5N8 there are three structural isomers:
SN2SNSN2SNSN2;CH2C (CH3) SNSN2;SN3SNSNSN2.
diene hydrocarbons: nomenclature
To name diene are two nomenclatures - historical (eg, divines Allen) and the IUPAC (International Union of theoretically and Applied Chemistry).According to the IUPAC nomenclature, first called diene corresponding alkane, in which name the suffix "an" is replaced by "diene", then the figures indicate the place of localization of the double bonds in the hydrocarbon chain.The numbering of the hydrocarbon chain is carried out so that the numbers have the lowest value.The above formula diene IUPAC 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) by catalytic dehydration of alkanes, dehydration method monohydric saturated alcohols.
Butadiene - a valuable raw material for producing synthetic rubbers (butadiene-acrylonitrile, butadiene, styrene), as well as perchlorovinyl.Isoprene - a substance with a characteristic odor.First isoprene produced from natural rubber by dry distillation.Isoprene was also prepared by dehydration of isopentane.Used to produce synthetic rubber, medicinal and aromatic substances.
rubber - elastic and very strong organic material, which is produced from natural raw materials (natural rubber) and synthetic methods (synthetic).Rubber-based molecules are diene conjugation with double bonds.During the processing of this material, and heating sulfur (vulcanizing) rubber is formed.Rubbers - a very important raw material for the production of tires and tubes, insulating strips, rubber mittens, shoes and other objects used in the industry, economy and way of life, human and veterinary medicine.
ethylene hydrocarbons in the structure have a double bond.Sometimes these compounds are referred to olefins because the lower gaseous alkenes reacting with chlorine or bromine to form an oily compound, which are insoluble in water.
Acetylene hydrocarbons (alkynes) - compounds, which contain one triple bond.The greatest value of all the alkyne is acetylene, which is obtained by reacting calcium carbide with water.This gas is used for autogenous welding and cutting metals.Acetylene - a valuable raw material for the production of ethylene, ethanol, acetaldehyde, vinyl acetylene, acid acetate, benzene, trichloroethane, acrylonitrile.
