The first representative of alkenes is ethylene. Physical properties, production, application of ethylene
A bright representative of unsaturated hydrocarbons -ethene (ethylene). Physical properties: colorless combustible gas, explosive in a mixture with oxygen and air. In significant quantities, ethylene is produced from oil for the subsequent synthesis of valuable organic substances (monohydric and dihydric alcohols, polymers, acetic acid and other compounds).
The homologous series of ethylene, sp2-hybridization
Hydrocarbons, similar in structure and properties with ethenom, are called alkenes. Historically, another term for this group, olefins, was fixed. The general formula CMr.X2nreflects the composition of the entire class of substances. Its first representative is ethylene, in the molecule of which carbon atoms form not three, but only two x-bonds with hydrogen. Alkenes - unsaturated or unsaturated compounds, their formula C2X4. Only 2 p and 1 are mixed in form and energys-electron cloud of the carbon atom, in total three x-bonds are formed. This state is called sp2-hybridization. The fourth valence of carbon is preserved, in the molecule there is a π-bond. In the structural formula, the structural feature is reflected. But symbols for designating different types of communication on circuits are usually used the same - dashes or dots. The structure of ethylene determines its active interaction with substances of different classes. The addition of water and other particles is due to the rupture of a weak π-bond. The liberated valences are saturated due to the electrons of oxygen, hydrogen, halogens.
Ethylene: physical properties of the substance
Etene under normal conditions (normal atmosphericpressure and temperature of 18 ° C) is a colorless gas. It has a sweet (ethereal) odor, its inhalation exerts a narcotic effect on a person. Cures at -169.5 ° C, melts under the same temperature conditions. The ethane boils at -103.8 ° C. It ignites when heated to 540 ° C. The gas burns well, the flame is glowing, with faint soot. Ethylene dissolves in ether and acetone, much less in water and alcohol. The rounded molar mass of the substance is 28 g / mol. The third and fourth representatives of the homologous series of ethene are also gaseous substances. The physical properties of the fifth and the following alkenes differ, they are liquids and solids.
Preparation and properties of ethylene
German chemist Johann Becher accidentally usedEthyl alcohol in experiments with concentrated sulfuric acid. This was the first time eten was obtained in laboratory conditions (1680). In the middle of the XIX century, A.M. Butlerov gave the compound the name ethylene. Physical properties and chemical reactions have also been described by a famous Russian chemist. Butlerov proposed a structural formula that reflects the structure of matter. Methods of obtaining it in the laboratory:
- Catalytic hydrogenation of acetylene.
- Dehydrohalogenation of chloroethane in reaction with a concentrated alcoholic solution of a strong base (alkali) upon heating.
- Cleavage of water from molecules of ethyl alcohol (dehydration). The reaction takes place in the presence of sulfuric acid. Its equation is: H2C-CH2-OH → H2C = CH2 + H2O
- oil processing - cracking and pyrolysis of hydrocarbon raw materials;
- dehydrogenation of ethane in the presence of a catalyst. H3C-CH3→ H2C = CH2+ H2
The structure of ethylene explains its typical chemical reactions - the addition of particles by C atoms, which are at a multiple bond:
- Halogenation and hydrohalogenation. The products of these reactions are halogenated derivatives.
- Hydrogenation (saturation with hydrogen), the production of ethane.
- Oxidation to dihydric alcohol ethylene glycol. Its formula: OH-H2C-CH2-OH.
- Polymerization according to the scheme: n (H2C = CH2) → n (-H2C-CH2-).
Applications of ethylene
When fractional distillation of oil in large volumesethylene is obtained. The physical properties, structure, chemical nature of the substance make it possible to use it in the production of ethyl alcohol, halogenated derivatives, alcohols, oxide, acetic acid and other compounds. Ethylene is a polyethylene monomer, as well as the starting compound for polystyrene.
Dichloroethane, which is obtained from ethene and chlorine,is a good solvent used in the production of PVC (PVC). Polyethylene of low and high pressure is made of film, pipes, dishes, polystyrene - CD cases and other details. PVC is the basis of linoleum, waterproof raincoats. In agriculture, ethenom treats fruits before harvesting to accelerate maturation.