Propane, preparation, properties, and chemical reactions.
Propane, C3H8 – organic substance class alkanes. In nature, found in natural gas extracted from gas and gas condensate fields in oil and gas. Is also formed in the cracking of petroleum products.
Propane (lat. propanum) – organic matter class alkaneconsisting of three carbon atoms and eight hydrogen atoms.
Chemical formula propane C3H8, the rational formula is CH3CH2CH3. Isomers has not.
The structure of the molecule:
Propane – a colorless gas, without taste and smell. However, propane is used as a technical gas that can be added odorants – substances with a sharp odor to prevent its leakage.
In nature, found in natural gasextracted from gas and gas condensate fields in oil and gas. For the isolation of natural and associated petroleum gas produced by cleaning and separation of gas.
Is also formed in the cracking of petroleum products., including shale oil.
Also contained in shale gas and liquefied gas (liquefied natural gas).
Flammable and explosive.
Not soluble in water and other polar solvents. But soluble in some nonpolar organic substances (methanol, acetone, benzene, carbon tetrachloride, diethyl ether, etc.).
Low toxicity, but adverse effects in humans – Central nervous system (poisoning, vomiting, possible death). The fourth class of danger.
|Aggregate state (at 20 °C and atmospheric pressure of 1 ATM.)||gas|
|Density (at 20 °C and atmospheric pressure of 1 ATM.) kg/m3||1,8641|
|Density (at boiling point and atmospheric pressure 1 ATM.) kg/m3||585|
|Melting point, °C||-187,6|
|Boiling point, °C||-42,09|
|The auto-ignition temperature, °C||472|
|Critical temperature* To||370|
|Critical pressure, MPa||4,27|
|Critical specific volume, m3/kg||0,00444|
|Explosive concentration of the mixture of gas with air, % by volume||from 1.7 to 10.9|
|Specific heat of combustion, MJ/kg||48|
|Molar mass, g/mol||44.1 kHz|
* at temperatures above the critical temperature the gas cannot be condensed at any pressure.
Propane difficult chemical reactions. In normal conditions does not react with concentrated acids, melted and concentrated alkalis, alkali metals, Halogens (except fluorine), potassium permanganate and potassium dichromate in an acidic medium.
Chemical properties of propane are similar to properties of other representatives of a number of alkanes. So it is characterized by the following chemical reactions:
1. catalytic dehydrogenation of propane:
CH3-CH2-CH3 → CH2=CH-CH3 + H2 (kat = Pt, Ni, Al2O3, Cr2O3, to = 575 °C).
2. galogenirovannami propane:
CH3-CH2-CH3 + Br2 → CH3-CHBr-CH3 + HBr (hv or increased to);
CH3-CH2-CH3 + I2 → CH3-CHI-CH3 + HI (hv or increased to).
The reaction is self-perpetuating. A molecule of bromine or iodine under the action of light decomposes to the radicals, then they attack molecules of propane, taking from them an atom of hydrogen, this produces a free-propyl CH3-CH·-CH3, which collide with molecules of bromine (iodine), destroying them and forming new radicals of iodine or bromine:
Br2 → Br·+ Br· (hv); – initiation reactions of halogenation;
CH3-CH2-CH3 + Br· → CH3-CH·-CH3 + HBr; – the chain growth reactions of halogenation;
CH3-CH·-CH3 + Br2 → CH3-CHBr-CH3 + Br·;
CH3-CH·-CH3 + Br· → CH3-CHBr-CH3; – open circuit reactions of halogenation.
Galogenirovannami is one of the substitution reactions. First halogenides least gidrirovanny carbon atom (atom is tertiary, then secondary, primary atoms halogenide least). Galogenirovannami propane takes place in stages – one stage is replaced by one hydrogen atom.
CH3-CH2-CH3 + Br2 → CH3-CHBr-CH3 + HBr (hv or increased to);
CH3-CHBr-CH3 + Br2 → CH3-CBr2-CH3 + HBr (hv or increased to);
Galogenirovannami will continue until they are replaced by hydrogen atoms.
3. nitration of propane:
Cm. nitration of ethane.
4. the oxidation (burning) of propane:
With excess oxygen:
C3H8 + 5O2 → 3CO2 + 4H2O.
Burns with a yellow flame.
If there is insufficient oxygen instead of carbon dioxide (CO2) is a carbon monoxide (co), with a small number of finely dispersed oxygen is released and carbon (in various forms, including in the form of graphene, fullerenes , etc.) or a mixture thereof.
5. sulfochlorinated propane:
C3H8 + SO2 + Cl2 → C3H7-SO2Cl + … (hv).
6. sulfookislenie propane:
2C3H8 + 2SO2 + O2 → 2C3H7-ЅО2ОН (increased to).
Since the propane in sufficient quantity contained in natural gas, casinghead gas and is released when cracking of petroleum products, don’t get artificially. It is isolated in the purification and separation of natural gas, associated gas and oil by distillation.
Propane in the laboratory is the result of the following chemical reactions:
1. hydrogenation of unsaturated hydrocarbons, e.g. propene:
CH3-CH=CH2 + H2 → CH3-CH2-CH3 (kat = Ni, Pt or Pd, increased to).
2. recovery halogenoalkanes:
C3H7I + HI → C3H8 + I2 (increased to);
C3H7Br + H2 → C3H8 + HBr.
3. halogenoalkanes interaction with the metallic alkali metal, e.g., sodium (reaction furca):
C2H5Br + СН3Вг + 2Na → CH3-CH2-CH3 + 2NaBr;
C2H5CI + СH3Cl + 2Na → CH3-CH2-CH3 + 2NaCl.
The essence of this reaction is that two molecules halogenoalkane contact one, reacting with alkali metal.
4. decarboxylation of butyric acid and its salts:
C3H7-COOH + NaOH → C3H8 + Na2CO3 (increased to);
C3H7-COONa + NaOH → C3H8 + NaHCO3.
as fuel in households for cooking, vehicles, heating devices, etc. As a fuel propane is more convenient than methane. Propane liquefies at room temperature and a pressure of 12-15 atmospheres, which makes possible its storage and transportation in both normal and lighter – composite cylinders;
– to conduct various technological operations, for example, gas-flame works;
– as a raw material in the chemical industry for the production of other chemicals, e.g., solvents, polypropylene;
– in the food industry as a food additive E944 used as a propellant;
– as a refrigerant in refrigerators, freezers, refrigeration systems and air conditioning systems air. Used in the mixture with isobutane. Unlike other refrigerants, the mixture does not destroy the ozone layer.
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