Saturated hydrocarbons (paraffins) are limiting aliphatic hydrocarbons, where there is a simple (single) bond between carbon atoms.
All other valencies are saturated to the full with hydrogen atoms.
The saturated saturated hydrocarbons have a commonthe formula CnH2n + 2. Under normal conditions, representatives of this class show a weak reactivity, so they are called "paraffin". Saturated hydrocarbons start with methane, which has the molecular formula CH4.
This organic substance is odorlessand color, gas is almost twice as lighter than air. In nature it is formed during the decomposition of animals and plant organisms, but only in the absence of air access. It is found in coal mines, in swampy water bodies. In small quantities, methane is a part of natural gas, currently used as fuel in production, in everyday life.
This saturated hydrocarbon, belonging to the class of alkanes, has a covalent polar bond. The tetrahedral structure is explained by sp3 hybridization of the carbon atom, the valence angle is 109 ° 28 ".
Saturated hydrocarbons can be named bysystematic nomenclature. There is a certain order of actions, allowing to take into account all the branchings that exist in the molecule of the ultimate hydrocarbon. First, you need to identify the longest carbon chain, then number the carbon atoms. To do this, select the part of the molecule in which there is a maximum branching (more radicals). In the presence of several identical radicals in the alkane, with their name, specify the prefixes: di-, tri-, tetra. To clarify the position of active particles in a hydrocarbon molecule, use figures. The final stage in the name of paraffins is the indication of the carbon chain itself, with the addition of the suffix -an.
Saturated hydrocarbons differ in aggregatestate. The first four representatives of this cash register are gaseous compounds (from methane to butane). As the relative molecular weight increases, a transition occurs to the liquid, and then to the solid aggregate state.
Saturated and unsaturated hydrocarbons do not dissolve in water, but can dissolve in molecules of organic solvents.
What types of isomerism are saturated hydrocarbons? Examples of the structure of representatives of this class, starting with butane, indicate the presence of isomerism of the carbon skeleton.
The carbon chain formed by covalentpolar connections, has a zigzag appearance. This is the reason for the change in the basic chain in space, that is, the existence of structural isomers. For example, with a change in the arrangement of atoms in the butane molecule, its isomer-2-methylpropane is formed.
Let's consider the basic chemical propertiessaturated hydrocarbons. For the representatives of this class of hydrocarbons, the addition reactions are not characteristic, since all bonds in the molecule are single (saturated). Alkanes enter into interactions connected with the replacement of the hydrogen atom by halogen (halogenation), nitro group (nitration). If the formulas of saturated hydrocarbons are of the form CnH2n + 2, then after substitution a substance of the composition CnH2n + 1CL, and also CnH2n + 1NO2 is formed.
The substitution process is free radicalmechanism. First, active particles (radicals) are formed, followed by the formation of new organic substances. In reaction with the representatives of the seventh group (the main subgroup) of the periodic table, all alkanes enter, but the process proceeds only at elevated temperature, or in the presence of a quantum of light.
Also for all representatives of the methane seriescharacteristic is the interaction with oxygen in the air. During combustion, carbon dioxide, water vapor acts as reaction products. The reaction is accompanied by the formation of a significant amount of heat.
When methane reacts with oxygen in the airan explosion is possible. A similar effect is characteristic for other representatives of the class of limiting hydrocarbons. That's why a mixture of butane with propane, ethane, methane is dangerous. For example, such clusters are characteristic of coal mines, manufacturing workshops. In the case of heating of more than 1000 ° C of the ultimate hydrocarbon, its decomposition takes place. Higher temperatures lead to the production of unsaturated hydrocarbons, as well as the formation of hydrogen gas. The process of dehydrogenation is of industrial importance, it makes it possible to obtain a variety of organic substances.
For hydrocarbons of methane series, starting with butane, isomerization is characteristic. Its essence consists in changing the carbon skeleton, obtaining saturated hydrocarbons of a branched nature.
Methane as a natural gas is used inform of fuel. Chlorine derivatives of methane are of great practical importance. For example, chloroform (trichloromethane) and iodoform (triiodomethane) are used in medicine, and carbon tetrachloride stops evaporation of air during evaporation, so it is used to extinguish fires.
Due to the large value of the calorific value of hydrocarbons, they are used in the form of fuel not only in industrial production, but also for domestic purposes.
A mixture of propane and butane, called "liquefied gas", is particularly relevant in the area where there is no possibility of using natural gas.
Representatives of hydrocarbons in liquidare combustible for internal combustion engines in cars (gasoline). In addition, methane is an available raw material for various chemical industries.
For example, the decomposition and combustion of methaneis used for the industrial production of carbon black, which is necessary for the production of printing ink, as well as the synthesis of rubber from various rubber products.
To do this, the furnace is supplied with methanethe volume of air so that partial combustion of the saturated hydrocarbon takes place. As the temperature rises, part of the methane will decompose, with the formation of finely dispersed soot.
Methane is the main source of hydrogen in the industry used for the synthesis of ammonia. In order to conduct dehydrogenation, methane is mixed with water vapor.
The process takes place at a temperature of about 400 ° C,pressure of the order of 2-3 MPa, aluminum and nickel catalysts are used. In some syntheses a mixture of gases is used, which is formed in this process. If subsequent conversions involve the use of pure hydrogen, then catalytic oxidation of carbon monoxide by steam is carried out.
When chlorinated, a mixture of chlorine derivativesmethane, having a wide industrial application. For example, chloromethane is able to absorb heat, so it is used as a refrigerant in modern refrigeration plants.
Dichloromethane is a good solvent of organic substances, used in chemical synthesis.
Hydrogen chloride formed in the processradical halogenation, after dissolution in water, becomes hydrochloric acid. At present methane is also produced by acetylene, which is a valuable chemical raw material.
Representatives of the homologous series of methane widelyare distributed in nature, which makes them a demanded substance in many branches of modern industry. From homologues of methane, it is possible to produce hydrocarbons of branched structure, which are necessary for the synthesis of various classes of organic substances. The highest representatives of the alkane class are the raw materials for the production of synthetic detergents.
In addition to paraffins, alkanes, practical interestrepresent also cycloalkanes, called cycloparaffins. Their molecules also contain simple bonds, but the peculiarity of representatives of this class is the presence of a cyclic structure. Both alkanes and cycloacans are used in large quantities as a gaseous fuel, as the processes are accompanied by the release of a significant amount of heat (exothermic effect). At present, alkanes and cycloalkanes are considered to be the most valuable chemical raw materials, therefore their practical use is not limited to typical combustion reactions.
