Saturated hydrocarbons (paraffins) are saturated aliphatic hydrocarbons where a simple (single) bond exists between carbon atoms.
All other valencies are fully saturated with hydrogen atoms.
Homological series
The saturated saturated hydrocarbons have the general formula SpN2p + 2. Under ordinary conditions, representatives of this class exhibit weak reactivity, so they are called "paraffins." Saturated hydrocarbons begin with methane having the molecular formula CH4.
Structural features on the example of methane
This organic substance has no smell and color, gas is almost twice 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 marshy ponds. In small quantities, methane is a part of natural gas, which is currently used as fuel in production and in everyday life.
This saturated hydrocarbon, which belongs 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 '.
Paraffin Range
Saturated hydrocarbons can be called systematic nomenclature. There is a certain procedure that allows you to take into account all the branches available in the saturated hydrocarbon molecule. First you need to identify the longest carbon chain, then perform the numbering of carbon atoms. To do this, select the part of the molecule in which there is a maximum branching (more radicals). If there are several identical radicals in the alkane, their prefixes are indicated with their name: di-, tri-, tetra. To clarify the position of active particles in a hydrocarbon molecule, numbers are used. The final step in the name of paraffins is to indicate the carbon chain itself, with the suffix –an added.
Saturated hydrocarbons differ in the state of aggregation. The first four representatives of this box office are gaseous compounds (from methane to butane). As the relative molecular weight increases, a transition to the liquid and then to the solid state of aggregation occurs.
Saturated and unsaturated hydrocarbons do not dissolve in water, but are able to dissolve in molecules of organic solvents.
Features of isomerism
What types of isomerism do saturated hydrocarbons have? Examples of the structure of representatives of this class, starting with butane, indicate the presence of an isomerism of the carbon skeleton.
The carbon chain formed by covalent polar bonds has a zigzag shape. This is the reason for the change in the main chain in space, that is, the existence of structural isomers. For example, when the arrangement of atoms in a butane molecule changes, its isomer, 2 methylpropane, is formed.
Chemical properties
Consider the basic chemical properties of saturated hydrocarbons. Representatives of this class of hydrocarbons are not characterized by addition reactions, since all bonds in the molecule are single (saturated). Alkanes enter into interactions associated with the replacement of a hydrogen atom by a halogen (halogenation), a nitro group (nitration). If the saturated hydrocarbon formulas have the form SpH2n + 2, then after substitution a substance of the composition CnH2n + 1CL, as well as CnH2n + 1NO2, is formed.
The substitution process has a free radical mechanism. First, active particles (radicals) are formed, then the formation of new organic substances is observed. All alkanes enter into a reaction with representatives of the seventh group (main subgroup) of the periodic table, but the process proceeds only at elevated temperature, or in the presence of a quantum of light.
Also, all representatives of the methane series are characterized by interaction with atmospheric oxygen. During combustion, carbon dioxide and water vapor act as reaction products. The reaction is accompanied by the formation of a significant amount of heat.
The interaction of methane with oxygen is possible explosion. A similar effect is also characteristic of other representatives of the class of saturated hydrocarbons. That is why a mixture of butane with propane, ethane, methane is dangerous. For example, such clusters are characteristic of coal mines, production workshops. In the case of heating more than 1000 ° C of the saturated hydrocarbon, it decomposes. Higher temperatures result in unsaturated hydrocarbons, as well as hydrogen gas. The dehydrogenation process is of industrial importance, it allows you to get a variety of organic substances.
Hydrocarbons of a series of methane, starting with butane, are characterized by isomerization. Its essence is to change the carbon skeleton, to obtain branched saturated hydrocarbons.
Application features
Methane as natural gas is used as fuel. Of great practical importance are chlorine derivatives of methane. For example, chloroform (trichloromethane) and iodoform (triiodomethane) are used in medicine, and carbon tetrachloride during the evaporation process stops the access of atmospheric oxygen, 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 especially relevant in areas where it is not possible to use natural gas.
Interesting Facts
Representatives of hydrocarbons in a liquid state are fuel for internal combustion engines in automobiles (gasoline). In addition, methane is an affordable raw material for various chemical industries.
For example, the decomposition and combustion reaction of methane is used for the industrial production of soot, necessary for the production of printing ink, as well as the synthesis of various rubber products from rubber.
For this, such a volume of air is supplied to the furnace together with methane that partial combustion of the saturated hydrocarbon takes place. With increasing temperature, part of the methane will decompose, with the formation of fine soot.
The formation of hydrogen from paraffins
Methane is the main source of industrial production of hydrogen used for the synthesis of ammonia. In order to carry out dehydrogenation, methane is mixed with water vapor.
The process proceeds at a temperature of about 400 ° C, a pressure of about 2-3 MPa, and 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 the carbon monoxide is oxidized by steam.
When chlorination is obtained, a mixture of methane chlorine derivatives having wide industrial application. For example, chloromethane is capable of absorbing heat, which is why it is used as a refrigerant in modern refrigeration units.
Dichloromethane is a good solvent for organic substances, used in chemical synthesis.
Hydrogen chloride formed during radical halogenation, after dissolution in water, becomes hydrochloric acid. At present, acetylene, which is a valuable chemical raw material, is also obtained from methane.
Conclusion
Representatives of the homological series of methane are widely distributed in nature, which makes them demanded substances in many branches of modern industry. Branched hydrocarbons that are necessary for the synthesis of various classes of organic substances can be obtained from methane homologues. The highest representatives of the alkane class are the raw material for the production of synthetic detergents.
In addition to paraffins, alkanes, cycloalkanes called cycloparaffins are of practical interest. Their molecules also contain simple bonds, but the peculiarity of the representatives of this class is the presence of a cyclic structure. Both alkanes and cycloacanes are used in large quantities as gaseous fuel, since the processes are accompanied by the release of a significant amount of heat (exothermic effect). At present, alkanes, cycloalkanes are considered to be the most valuable chemical raw material; therefore, their practical use is not limited to typical combustion reactions.