Propane is an organic compound, the third representative of alkanes in the homologous series. At room temperature, it is a gas without color and odor. The chemical formula of propane is C 3 H 8 . Fire and explosion hazard. It has little toxicity. It has a weak effect on the nervous system and has narcotic properties.
Structure
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 axis of bonds, there are several molecular conformations. The bonds in the molecule are covalent: CC nonpolar, CH weakly polar. Because of this, they are difficult to break, and the substance is quite difficult to enter into chemical reactions. This sets all the chemical properties of propane. He has no isomers. The molar mass of propane is 44.1 g / mol.
Production methods
In industry, propane is hardly synthesized artificially. It is isolated from natural gas and oil by distillation. For this, there are special production facilities.
In the laboratory, propane can be obtained by the following chemical reactions:
- Hydrogenation of propene. This reaction occurs only with increasing temperature and in the presence of a catalyst (Ni, Pt, Pd).
- Reduction of alkane halides. Different reagents and conditions are used for different halides.
- Wurz synthesis. Its essence is that two halogenated molecules are bound together into one, reacting with an alkali metal.
- Decarboxylation of butyric acid and its salts.
Physical properties of propane
As already mentioned, propane is a gas without color and odor. It is not soluble in water and other polar solvents. But it is soluble 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. It is carried out at 575 ° C using a catalyst of chromium oxide (III) or alumina.
- Halogenation. For chlorination and bromination, ultraviolet radiation or elevated temperature is needed. Chlorine predominantly replaces the extreme hydrogen atom, although the substitution of the middle occurs in some molecules. An increase in temperature can lead to an increase in the yield of 2-chloropropane. Chlorpropane can be halogenated further with the formation of dichloropropane, trichloropropane and so on.
The mechanism of halogenation reactions is chain. Under the influence of light or high temperature, a halogen molecule breaks up into radicals. They interact with propane, taking away the hydrogen atom from it. As a result, free cut is formed. It interacts with a halogen molecule, again breaking it into radicals.
Bromination occurs by the same mechanism. Iodination 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 diluted nitric acid (Konovalov reaction) or nitric oxide (IV) at elevated temperature (130-150 ° C).
Sulfoxidation and sulfochlorination is carried out under UV light.
Propane combustion reaction: C 3 H 8 + 5O 2 → 3CO 2 + 4H 2 O.
Mild oxidation can also be carried out using certain catalysts. The propane combustion reaction will be different. In this case, propanol, propanal or propionic acid is obtained. As oxidizing agents, in addition to oxygen, peroxides (most often hydrogen peroxide), transition metal oxides, chromium (VI) and manganese (VII) compounds can be used.
Propane reacts with sulfur to form isopropyl sulfide. For this, tetrabromoethane and aluminum bromide are used as catalysts. This reaction takes place at 20 ° C for two hours. The reaction yield is 60%.
With the same catalysts, it can react with carbon monoxide (I) to form 2-methylpropanoic acid isopropyl ester. The reaction mixture after the reaction should be treated with isopropanol. So, we examined the chemical properties of propane.
Application
Due to its good combustibility, propane is used as a fuel in households and industry. It can also be used as fuel for cars. Propane burns with a temperature of almost 2000 ° C, so it is used for welding and cutting metal. Propane burners heat bitumen and asphalt in road construction. But often on the market not pure propane is used, but its mixture with butane (propane-butane).
Oddly enough, but he found application in the food industry as an additive E944. Due to its chemical properties, propane is used there as a solvent for flavorings, as well as for the treatment of oils.
A mixture of propane and isobutane is used as R-290a refrigerant. It is more effective than old refrigerants, and is also environmentally friendly, as it does not destroy the ozone layer.
Propane has found great application in organic synthesis. It is used to produce polypropylene and various solvents. In oil refining, it is used for deasphalting, that is, to reduce the proportion of heavy molecules in the bitumen mixture. This is necessary for the recycling of old asphalt.