Propane is an organic compound, the third representative of alkanes in the homologous series. At room temperature, it is a colorless and odorless gas. The chemical formula of propane is C3H8. Fire and explosion hazard. It has little toxicity. It has a mild effect on the nervous system and has narcotic properties.
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Propane is a saturated hydrocarbon consisting of three carbon atoms. For this reason, it has a curved shape, but due to the constant rotation around the bond axes, there are several molecular conformations. The bonds in the molecule are covalent: C-C non-polar, C-H weakly polar. Because of this, they are difficult to break, and the substance is rather difficult to enter into chemical reactions. This sets all the chemical properties of propane. It has no isomers. The molar mass of propane is 44.1 g/mol.
Methods of obtaining
Propane is almost never synthesized artificially in industry. It is isolated from natural gas and oil by distillation. For this there arespecial production units.
In the laboratory, propane can be obtained by the following chemical reactions:
- Hydrogenation of propene. This reaction occurs only when the temperature rises and in the presence of a catalyst (Ni, Pt, Pd).
- Reduction of alkane halides. Different halides use different reagents and conditions.
- Wurtz Synthesis. Its essence is that two haloaclkane molecules bind into one, reacting with an alkali metal.
- Decarboxylation of butyric acid and its s alts.
Physical properties of propane
As already mentioned, propane is a colorless and odorless gas. It is insoluble in water and other polar solvents. But it dissolves in some organic substances (methanol, acetone and others). At -42, 1 °C it liquefies, and at -188 °C it becomes solid. Flammable, as it forms flammable and explosive mixtures with air.
Chemical properties of propane
They represent typical properties of alkanes.
- Catalytic dehydrogenation. Carried out at 575 °C using a chromium (III) oxide or alumina catalyst.
- Halogenation. Chlorination and bromination require ultraviolet radiation or elevated temperature. Chlorine predominantly replaces the outer hydrogen atom, although in some molecules the middle one is replaced. An increase in temperature can lead to an increase in the yield of 2-chloropropane. Chloropropane can be further halogenated to form dichloropropane, trichloropropane, and so on.
The mechanism of halogenation reactions is chain. Under the action of light or high temperature, the halogen molecule decomposes into radicals. They interact with propane, taking away a hydrogen atom from it. As a result, a free cut is formed. It interacts with the halogen molecule, again breaking it into radicals.
Bromination occurs by the same mechanism. Iodization can only be carried out with special iodine-containing reagents, since propane does not interact with pure iodine. When interacting with fluorine, an explosion occurs, a polysubstituted propane derivative is formed.
Nitration can be carried out with dilute nitric acid (Konovalov reaction) or nitric oxide (IV) at elevated temperature (130-150 °C).
Sulfonic oxidation and sulphochlorination is carried out with UV light.
Propane combustion reaction: C3H8+ 5O2 → 3CO 2 + 4H2O.
It is also possible to carry out milder oxidation using certain catalysts. The combustion reaction of propane will be different. In this case, propanol, propanal or propionic acid are obtained.acid. In addition to oxygen, peroxides (most often hydrogen peroxide), transition metal oxides, chromium (VI) and manganese (VII) compounds can be used as oxidizing agents.
Propane reacts with sulfur to form isopropyl sulfide. For this, tetrabromoethane and aluminum bromide are used as catalysts. The reaction proceeds at 20 °C for two hours. The reaction yield is 60%.
With the same catalysts it can react with carbon monoxide (I) to form isopropyl ester of 2-methylpropanoic acid. The reaction mixture after the reaction must be treated with isopropanol. So, we have considered the chemical properties of propane.
Application
Because of its good flammability, propane is used in everyday life and industry as a fuel. It can also be used as fuel for cars. Propane burns at almost 2000°C, which is why it is used for welding and cutting metal. Propane burners heat bitumen and asph alt in road construction. But often the market does not use pure propane, but its mixture with butane (propane-butane).
Strange as it may seem, it has also found application in the food industry as an additive E944. Due to its chemical properties, propane is used there as a solvent for fragrances and also for the treatment of oils.
A mixture of propane and isobutane is used as the refrigerant R-290a. It is more efficient than older refrigerants and is also environmentally friendly as it does not deplete the ozone layer.
Great applicationpropane found in organic synthesis. It is used to produce polypropylene and various kinds of solvents. In oil refining, it is used for deasph alting, that is, reducing the proportion of heavy molecules in the bitumen mixture. This is necessary for the recycling of old asph alt.
