Saturated hydrocarbons: properties and applications
First, we consider saturated hydrocarbons, their structural features, properties, and applications.
General information about alkanes
This class includes compounds that meet the general formula CnH2n + 2. Their molecules are linear, only a simple bond is characteristic of them.
Limit hydrocarbons are represented by a homologous series of methane. Between the carbon atoms in their molecules sp3 hybridization, which is characterized by an angle of 109 degrees.
Being in nature
Limit hydrocarbons are widely distributed in nature. For example, methane, the head of this class of ShNu, is formed by the decomposition of animal and plant organisms in swampy areas (without access to air).
In addition, this compound is present in coal mines, which often leads to serious explosions and the death of miners.
Limit hydrocarbons in large quantities are contained in solid, liquid, and also gaseous form in oil.In addition to methane, there is propane, ethane, butane, and pentane in oil.
Physical properties of alkanes
These substances are slightly soluble in water. The lowest members of the series are gases. With an increase in the relative molecular weight of compounds, an increase in boiling and melting points is observed, a transition from a gaseous state to liquids and solids occurs.
Consider the basic chemical properties of saturated hydrocarbons. Due to the low polarity of the C – C bond, they are chemically inactive compounds.
Among the characteristic properties of representatives of this class, we note radical halogenation. As a result of the interaction in the first stage, a monohalogeno-derivative is formed, as well as hydrogen halide. Given that the reaction has a chain mechanism, the substitution continues until halogen atoms appear in place of the hydrogens.
In addition to halogenation, saturated hydrocarbons react with nitric acid. Nitration leads to the formation of nitroalkanes.
Sulfuration is associated with the replacement of a hydrogen atom by a sulfo group; among the reaction products will be alkanesulphonic acid and water.The process is carried out with a slight heating of the reaction mixture, sulfuric acid is taken in a concentrated form.
Under normal conditions, alkanes exhibit resistance to such strong oxidizing agents as potassium permanganate, potassium dichromate.
When the temperature rises, their oxidation with air oxygen to carbon monoxide (4) and water vapor is observed.
Incomplete (catalytic) oxidation leads to the formation of ketones, aldehydes, carboxylic acids.
When C – C bonds break, cracking occurs, as a result of which compounds with a smaller number of carbon atoms are formed from a long carbon chain.
Among the products of the dehydrogenation of unsaturated hydrocarbons and hydrogen molecules, the reaction occurs at high temperatures.
During dehydrocyclization, aromatic hydrocarbons are formed, which have practical application.
Limit and unsaturated hydrocarbons may have a cyclic or aliphatic structure. For example, alkenes having the general formula CnH2n are distinguished by the presence of double bonds between carbon atoms.
That is why for the representatives of a number of ethylene characteristic reactions of addition to the double bond.Hydrohalogenation and hydration are carried out for asymmetric alkenes according to the Markovnikov rule. Its essence is that when joining by a double bond of a hydrogen halide or water, the halogen atoms or hydroxo groups are attached to the carbon that has a smaller number H, and the hydrogen goes to the first atom C.
In addition, representatives of this class of organic compounds are characterized by a polymerization reaction. It has found wide application in the modern chemical industry. For example, for the production of polyethylene, which is in demand in agriculture, medicine, ethylene is taken as the initial monomer. In a catalytic polymerization process, a double bond is observed, eventually forming a polymeric compound.
The qualitative reaction to unsaturation (the presence of double and triple bonds in the molecules) is the bleaching of bromine (iodine) water, as well as the bleaching of potassium permanganate solution.
Among cyclic hydrocarbons, which are now widely used, should be mentioned benzene and toluene. These ShNu are typical representatives of a number of aromatic hydrocarbons, which have the general formula CnH2n-6.
Benzene, in which the electron density is uniformly distributed, is considered a low-active compound. Toluene used for the industrial production of benzoic acid, which is an excellent preservative, has a greater reactivity.
In organic chemistry, several classes of hydrocarbons are distinguished, differing in the arrangement of carbon atoms and the presence of single and double (triple) bonds. Despite significant differences in structure, physical and chemical properties, they are all in demand in various industries. Among saturated hydrocarbons, methane and its nearest homologs are of particular interest.
Among diene compounds, the leading indicators in the production of polymeric materials are 1.3-butadiene and 2-methylbutadiene-1.3. Of particular interest are aromatic hydrocarbons. They are the basis for the production of organic dyes, preservatives.