Synthetic rubber, ethyl alcohol, acetic acid, polyvinyl chloride resins, benzene - this is not a complete list of the most important chemical compounds. They are produced by the organic synthesis industry. These products are obtained from acetylene. The chemical properties of unsaturated hydrocarbons with a triple bond, to which this substance belongs, determine their ability to reactions of addition, oxidation and polymerization. Separately, it must be said about the high energy intensity of gas.
Therefore, ethine mixed with oxygen is used in the welding of metal parts. They can be made of cast iron, steel and non-ferrous metals. Acetylene combustion can be controlled, which is a big advantage. The substance is used as a raw material for the production of polymers, solvents, fibers and other valuable materials. The presence of double bonds in a molecule provides the ability to attach atoms of other chemical elements. Combustion releases a lot of heat. In our article, we will study in detail the chemical properties of acetylene, also called ethine, listed above, and also find out how to obtain it in industry.
How the structure of a molecule determines the properties of organic matter
The linear ethine molecule contains two carbon atoms, interconnected by one sigma and two pi bonds. Carbon atoms are in a state of sp hybridization. Two hydrogen atoms together with the carbon skeleton are located in the plane of the molecule, and double bonds are oriented in mutually perpendicular planes. Acetylene reactions, such as the oxidation of bromine water or the addition of hydrogen halides, occur at the site of rupture of pi bonds. Compared with a number of ethylene substances, these processes are much more active in alkynes. This is due to the presence of a triple bond in their molecules. She also explains the fact that the addition reaction is carried out in two stages: first, compounds of a series of ethene are formed, then the final product related to saturated hydrocarbons or their halogenated derivatives.
Physical Characterization and Receipt
The aggregate form of ethine under ordinary conditions is gas. Acetylene is lighter than air and poorly soluble in water. Its formula is C 2 H 2 , the molecular weight is 26 g / mol. The substance boils at a temperature of about 83.8 ° C. Like any gas, it can be compressed under pressure, but the process is accompanied by an explosion. The connection is very energy intensive, the specific heat of combustion is equal to 14000 kcal / m 3 . Acetylene is obtained from calcium carbide or ethane.
The main and cost-effective industrial method for producing hydrocarbon is pyrolysis. It has several varieties, among which the most promising are homogeneous and oxidative processes. The feedstock in them is methane, the molecules of which are dehydrated. For a long time, the carbide method has been used in chemistry. Here, calcium carbide and water react with each other. Acetylene obtained by this method, which is very important, practically does not contain impurities. However, the process itself is energy intensive and requires high energy consumption.
Hydrogenation reaction
An example of a heterogeneous catalytic reaction characteristic of unsaturated hydrocarbons with a triple bond between carbon atoms is their interaction with hydrogen. Heating and the presence of a nickel catalyst are the main conditions for hydrogenation. As we said earlier, addition reactions are inherent in the chemical properties of acetylene. They pass in two stages.
First, one pi bond breaks and two hydrogen atoms join the free valencies of the carbon atoms. An alkene is formed, in this case ethylene. Then there is the destruction of one unsaturated bond in its molecule and there is a limit connection - ethane. Acetylene, as we see, as a result of hydrogenation, completely lost double bonds and turned into a saturated hydrocarbon.
Qualitative reaction to ethine
In organic chemistry, reactions are used to determine the presence in a substance of a certain complex of atoms or a type of chemical bond. They are called quality. To prove the presence of two unsaturated pi bonds in alkynes, a reagent such as bromine water is used. Acetylene is passed through a Br 2 brown solution and discoloration is observed. Get a product - tetrabromoethane, which refers to substances - halogenated saturated hydrocarbons.
Polyvinyl chloride resins
Of great practical importance is the reaction of the addition of hydrogen chloride to ethine, which in the first stage ends with the formation of chlorovinyl. Its molecules retain a double bond in their composition, which ensures their ability to connect with each other and form a polymer.
The chemical properties of acetylene, in particular the polymerization reaction of its derivative - chlorovinyl, made it possible to create a whole group of substances with unique technical characteristics. For example, thermovil and fibrovil - fibers used to produce heavy-duty fabrics used in sewing workwear. Modern construction, drainage and finishing works cannot be imagined without PVC pipes, foams and floor coverings. They are lightweight, durable, resistant to corrosion and much cheaper than products made from natural materials: metal or wood.
The reaction of M. G. Kucherov
Speaking about the well-known chemical properties of a substance, for example, polymerization, addition or combustion of acetylene, we mentioned that the gas is practically insoluble in water. However, in the presence of mercury nitrate or sulfate as a catalyst, a reaction occurs that was first carried out in the 19th century by the famous Russian scientist M. G. Kucherov. In it, the product of the interaction between water and ethine is acetic aldehyde. It, in turn, refers to the compounds most in demand in industry, as it serves as a raw material for the production of ethyl alcohol in the reduction reaction.
If acetaldehyde is oxidized, then we get another important organic substance - acetic acid. Recently, the reaction of M. G. Kucherov is used on a smaller scale due to the toxicity of the catalyst used. Now more and more often ethane is used as a feedstock. Acetylene is obtained as a result of its dehydrogenation.
In our article, we examined the basic chemical properties and production of acetylene, as well as its use in industry.