saturated hydrocarbons or paraffin, called such biosoedineniya whose molecules of carbon atoms connected by a simple (single) bond, while all other units valences are saturated with hydrogen atoms.
Alkanes: physical properties
first representatives of the homologous series of methane - gases from S5N12 to S15N32 - liquid, since S16N34 - solids.With the increasing number of carbon atoms in the alkane molecule naturally increase their melting point and boiling point.
boiling point hydrocarbons with a branched chain is much lower than a boiling point of isomers.Methane and ethane are odorless, volatile liquid hydrocarbons are gasoline odor (pentane and hexane) and kerosene, higher homologs thereof have methane.Saturated hydrocarbons lighter than water and practically insoluble in it.Saturated hydrocarbons are readily soluble in organic solvents, and liquid alkanes themselves are excellent solvents.
Alkanes: chemical properties
For these biosoedineny characteristic small reactivity.They are inert, that is displayed in their title - paraffins.This is because in the structure of the molecules C and H atoms linked sigma bonds.The chemical inertness of these substances due to the peculiarities of the structure of the molecules.To break sigma bonds necessary to spend much energy.Basic chemical.properties alkanes, i.e. a reaction in which they enter, this nitration reaction, halogenation, sulfonation, sulfochlorination, cracking.Alkane radical reactions initiated by radicals, UV or gamma radiation, peroxides, heating.In this regard, they are characterized by two types of reactions: substitution of hydrogen bond breaking "carbon-hydrogen" and cleavage of the molecule with the rupture of the C-C or C-H.
Alkanes: chemical properties.The reaction of radical halogenation
This reaction is sometimes called metalepsiey.It can be triggered by sunlight.The dark at 250-400 ° C or in the presence of catalysts (copper chloride, tin chloride) halogen atoms replace hydrogen atoms in series in alkane molecules.
Alkanes: chemical properties.Nitration reaction
nitro group is easily substituted for hydrogen in the tertiary, secondary and harder very hard in primary carbon atoms.Now industrial scale nitration of alkanes is carried out in the gas phase at 150-490 ° C with nitric oxide or nitric acid vapors.
Alkanes: chemical properties.Reaction sulfochlorination
on saturated hydrocarbons to a mixture of sulfur dioxide and chlorine.Catalysts are often peroxides or UV radiation.This reaction is used to produce detergents (detergents).On alkilsulfohloridy alkalis, which leads to the formation of alkaline salts of sulphonic acids, the structural components of detergents (pastes, powders).
Saturated hydrocarbons - the raw material for the synthesis of various organic substances.A prerequisite for the synthesis of many of them is the preparation of alkenes from alkanes, or unsaturated hydrocarbons.
Cleavage of hydrogen from the molecule of an alkane or dehydrogenation in the presence of catalysts and under heating (460 ° C) allows to obtain the required alkenes.Methods of oxidation of alkanes at low temperatures in the presence of catalysts (magnesium salts).This allows directionally affect the reaction and to obtain the required oxidation products during chemical synthesis.For example, in the oxidation of higher alkanes receive a variety of higher alcohols or higher fatty acids.
splitting alkanes also occurs in other conditions (burning, cracking).Saturated hydrocarbons are burning blue flame with the release of huge amounts of heat.These properties permit their use as a high-calorie fuel in the home and in industry.
