Methane butane propane hexane formula. What is propane-butane

If Vacation home is located not far from network highways, then the choice of heating system is obvious: on this moment natural gas is the most economical type of fuel. But even in the absence of a central gas supply, many homeowners prefer gas heating. For this purpose they are used autonomous systems, operating on liquefied gas.

The first member of the family is methane. It is formed by a carbon atom surrounded by 4 hydrogen atoms. Other members differ by the addition of a carbon atom. Names of the most famous. In conclusion, we note that alkanes have the following molecular formula. They are part of a series called homologous. This helps us understand their physical properties because once we know one, we can extrapolate the results to the others. Basic physical characteristics.

Ethane is extremely widespread (one of the permanent components of natural gas). It participates in all reactions characteristic of alkanes, primarily halogenation. It occurs under the influence of ultraviolet irradiation, during which free radical initiators are formed, and can be accelerated by heating. Ethylene is used in industry: it is a raw material for the production of dichloroethane, vinyl acetate, ethylene oxide, polyethylene of various grades, styrene, which, in turn, is used for the production of polystyrene. Also obtained from ethylene ethanol, acetic acid, ethylene glycol. Moreover, this gas is used to accelerate the ripening of vegetables and fruits.

If a country house is located not far from network highways, then the choice of heating system is obvious: at the moment, natural gas is the most economical type of fuel. But even with...

Saturated hydrocarbons of the methane series (alkanes)

Alkanes, or paraffins, are aliphatic saturated hydrocarbons in whose molecules the carbon atoms are linked together by a simple s - communication. The remaining valencies of the carbon atom, not spent on bonding with other carbon atoms, are completely saturated with hydrogen. Therefore, saturated hydrocarbons contain the maximum number of hydrogen atoms in the molecule.

Hydrocarbons of a number of alkanes have the general formula C n H 2n+2. The table shows some representatives of a number of alkanes and some of their physical properties.

Formula	Name	Radical name	T pl. 0 C	T kip. 0 C
CH 4	methane	methyl
C2H6	ethane	ethyl
C 3 H 8	propane	cut through
C4H10	butane	butyl
C4H10	isobutane	isobutyl
C5H12	pentane	pentyl
C5H12	isopentane	isopentyl
C5H12	neopentane	neopentyl
C6H14	hexane	hexyl
C 7 H 16	heptane	heptyl
C 10 H 22	dean	decile
C 15 H 32	pentadecane
C 20 H 42	eicosane

The table shows that these hydrocarbons differ from each other in the number of groups - CH 2 -. Such a series of similar structures, having similar chemical properties and differing from each other in the number of these groups is called homologous series. And the substances that make it up are called homologues .

Simulator No. 1 - Homologues and isomers

Trainer No. 2. - Homologous series of saturated hydrocarbons

Physical properties

First four members homologous series methane - gaseous substances, starting with pentane, are liquids, and hydrocarbons with a number of carbon atoms of 16 and higher are solids (at ordinary temperatures). Alkanes are non-polar compounds and difficult to polarize. They are lighter than water and practically insoluble in it. They also do not dissolve in other highly polar solvents. Liquid alkanes are good solvents for many organic matter. Methane and ethane, as well as higher alkanes, are odorless. Alkanes are flammable substances. Methane burns with a colorless flame.

Preparation of alkanes

Natural sources are mainly used to obtain alkanes.

Gaseous alkanes are obtained from natural and associated petroleum gases, and solid alkanes are from petroleum. A natural mixture of solid high molecular weight alkanes is mountain wax - natural bitumen.

1. From simple substances:

n C+2 n H 2 500 °C, cat → WITH n H 2 n + 2

2. The effect of metallic sodium on halogen derivatives of alkanes - reaction of A. Wurtz:

2CH 3 -Cl + 2Na → CH 3 -CH 3 + 2NaCl

Chemical properties of alkanes

1. Substitution reactions - Halogenation (stage by stage)

CH4+Cl2 hν → CH 3 Cl (chloromethane) + HCl (1st stage);

methane

CH 3 Cl + Cl 2 hν→ CH 2 Cl 2 (dichloromethane) + HCl (2nd stage);

C H 2 Cl 2 + Cl 2 hν → CHCl 3 (trichloromethane) + HCl (3rd stage);

CHCl 3 + Cl 2 hν → CCl 4 (chloromethane) + HCl (4th stage).

2. Combustion reactions (burn with a light, non-smoking flame)

C n H 2n+2 + O 2 t → nCO 2 + (n+1)H 2 O

3. Decomposition reactions

A) Cracking at a temperature of 700-1000°C (-C-C-) bonds are broken:

C 10 H 22 → C 5 H 12 + C 5 H 10

b) Pyrolysis at a temperature of 1000°C all bonds are broken, the products are C (soot) and H 2:

C H 4 1000°C → C+2H2

Application

· Saturated hydrocarbons are widely used in a wide variety of areas of human life and activity.

· Use as fuel - in boiler systems, gasoline, diesel fuel, aviation fuel, cylinders with a propane-butane mixture for household stoves

· Vaseline is used in medicine, perfumery, cosmetics; higher alkanes are found in lubricating oils; alkane compounds are used as refrigerants in home refrigerators

· A mixture of isomeric pentanes and hexanes is called petroleum ether and is used as a solvent. Cyclohexane is also widely used as a solvent and for the synthesis of polymers.

· Methane is used to produce tires and paint

· The meaning of alkanes in modern world huge. In the petrochemical industry, saturated hydrocarbons are the basis for the production of various organic compounds, an important raw material in the processes of obtaining intermediates for the production of plastics, rubbers, synthetic fibers, detergents and many other substances. It is of great importance in medicine, perfumery and cosmetics.

Tasks for consolidation

No. 1. Write down equations for the combustion reactions of ethane and butane.

№2. Write down reaction equations for the production of butane from the following haloalkanes:

CH 3 - Cl (chloromethane) and C 2 H 5 - I (iodoethane).

No. 3. Carry out the transformations according to the scheme, name the products:

C→ CH 4 → CH 3 Cl → C 2 H 6 → CO 2

No. 4. Solve the crossword

Horizontally:

1. An alkane having the molecular formula C 3 H 8.
2. The simplest representative saturated hydrocarbons.
3. French chemist, whose name is the reaction of producing hydrocarbons with a longer carbon chain by reacting halogen derivatives of saturated hydrocarbons with sodium metal.
4. Geometric figure, which resembles the spatial structure of the methane molecule.
5. Trichloromethane.
6. Name of the radical C 2 H 5 –.
7. Most characteristic appearance reactions for alkanes.
8. State of aggregation the first four representatives of alkanes under normal conditions.

If you answered the questions correctly, then in the highlighted column vertically get one of the names of saturated hydrocarbons. Name this word?

Alkanes (methane and its homologues) have the general formula C n H 2 n+2. The first four hydrocarbons are called methane, ethane, propane, butane. The names of the higher members of this series consist of the root - the Greek numeral and the suffix -an. The names of alkanes are the basis of IUPAC nomenclature.

Rules for systematic nomenclature:

Main chain rule.

The main circuit is selected based on the following criteria:

Maximum number functional substituents.
Maximum number of multiple connections.
Maximum length.
Maximum number of side hydrocarbon groups.

Rule of smallest numbers (locants).

The main circuit is numbered from one end to the other in Arabic numerals. Each substituent is assigned the number of the main chain carbon atom to which it is attached. The numbering sequence is chosen in such a way that the sum of the numbers of the substituents (locants) is the smallest. This rule also applies when numbering monocyclic compounds.

Radical rule.

All hydrocarbon side groups are considered as monovalent (single-connected) radicals. If the side radical itself contains side chains, then according to the above rules, an additional main chain is selected, which is numbered starting from the carbon atom attached to the main chain.

Alphabetical order rule.

The name of the compound begins with a list of substituents, indicating their names in alphabetical order. The name of each substituent is preceded by its number in the main chain. The presence of several substituents is indicated by numerator prefixes: di-, tri-, tetra-, etc. After this, the hydrocarbon corresponding to the main chain is named.

In table 12.1 shows the names of the first five hydrocarbons, their radicals, possible isomers and their corresponding formulas. The names of radicals end with the suffix -yl.

Formula		Name
hydrocarbon	radical	coal hydrogen	radical


			Isopropyl
		Methylpropane (iso-butane)	Methylpropyl (iso-butyl) Tert-butyl

		methylbutane (isopentane)	methylbutyl (isopentyl)
		dimethylpropane (neopentane)	dimethylpropyl (neopentyl)

Table 12.1.

Alkanes of the acyclopean series C n H 2 n +2 .

Example. Name all isomers of hexane.

Example. Name the alkane with the following structure

In this example, from two twelve-atom chains, the one in which the sum of the numbers is the smallest is selected (rule 2).

Using the names of branched radicals given in table. 12.2,

Radical	Name	Radical	Name
	isopropyl		isopentyl
	isobutyl		neopentyl
	sec-butyl		tert-pentyl
	tert-butyl		isohexyl

Table 12.2.

Names of branched radicals.

The name of this alkane is somewhat simplified:

10-tert-butyl-2,2-(dimethyl)-7-propyl-4-isopropyl-3-ethyl-dodecane.

When a hydrocarbon chain is closed in a cycle with the loss of two hydrogen atoms, monocycloalkanes are formed with general formula C n H 2 n. Cyclization starts with C 3, names are formed from C n with the cyclo prefix:

Polycyclic alkanes. Their names are formed using the prefix bicyclo-, tricyclo-, etc. Bicyclic and tricyclic compounds contain, respectively, two and three rings in the molecule, to describe their structure in square brackets indicate in decreasing order the number of carbon atoms in each of the chains connecting the node atoms; under the formula is the name of the atom:

This tricyclic hydrocarbon is usually called adamantane (from the Czech adamant - diamond) because it is a combination of three fused cyclohexane rings in a form resulting in this arrangement of carbon atoms in crystal lattice, which is characteristic of diamond.

Cyclic hydrocarbons with one common atom carbons are called spiranes, for example, spiro-5,5-undecane:

Planar cyclic molecules are unstable, so various conformational isomers are formed. Unlike configurational isomers (the spatial arrangement of atoms in a molecule without taking into account orientation), conformational isomers differ from each other only by the rotation of atoms or radicals around the formal simple connections while maintaining the configuration of the molecules. The energy of formation of a stable conformer is called conformational.

Conformers are in dynamic equilibrium and transform into each other through unstable forms. The instability of planar cycles is caused by significant deformation of bond angles. While maintaining the tetrahedral bond angles for cyclohexane C 6H 12, two stable conformations are possible: in the shape of a chair (a) and in the shape of a bath (b):

Hydrocarbons in which the atoms are bonded single bonds and which correspond to the general formula C n H 2 n +2.
In alkane molecules, all carbon atoms are in a state of sp 3 hybridization. This means that all four hybrid orbitals of the carbon atom are identical in shape, energy and are directed at equilateral angles. triangular pyramid- tetrahedron. The angles between the orbitals are 109° 28′.

Almost free rotation is possible around a single carbon-carbon bond, and alkane molecules can acquire the most various shapes with angles at carbon atoms close to tetrahedral (109° 28′), for example, in a molecule n-pentane.

It is especially worth recalling the bonds in alkane molecules. All bonds in the molecules of saturated hydrocarbons are single. The overlap occurs along the axis,
connecting the nuclei of atoms, i.e. these are σ bonds. Carbon-carbon bonds are non-polar and poorly polarizable. Length S-S connections in alkanes is 0.154 nm (1.54 10 - 10 m). C-H bonds are somewhat shorter. The electron density is slightly shifted towards the more electronegative carbon atom, i.e. C-H connection is weakly polar.

Absence of saturated hydrocarbons in molecules polar bonds leads to the fact that they are poorly soluble in water and do not interact with charged particles (ions). The most characteristic reactions for alkanes are those involving free radicals.

Homologous series of methane

Homologues- substances that are similar in structure and properties and differ by one or more CH 2 groups.

Isomerism and nomenclature

Alkanes are characterized by so-called structural isomerism. Structural isomers differ from each other in the structure of the carbon skeleton. The simplest alkane, which is characterized by structural isomers, is butane.

Nomenclature Basics

1. Selection of the main circuit. The formation of the name of a hydrocarbon begins with the definition of the main chain - the longest chain of carbon atoms in the molecule, which is, as it were, its basis.
2. Numbering of atoms of the main chain. The atoms of the main chain are assigned numbers. The numbering of the atoms of the main chain begins from the end to which the substituent is closest (structures A, B). If the substituents are located at an equal distance from the end of the chain, then numbering starts from the end at which there are more of them (structure B). If different substituents are located at equal distances from the ends of the chain, then numbering begins from the end to which the senior one is closest (structure D). The seniority of hydrocarbon substituents is determined by the order in which the letter with which their name begins appears in the alphabet: methyl (-CH 3), then ethyl (-CH 2 -CH 3), propyl (-CH 2 -CH 2 -CH 3 ) etc.
Please note that the name of the substituent is formed by replacing the suffix -an with the suffix - silt in the name of the corresponding alkane.
3. Formation of the name. At the beginning of the name, numbers are indicated - the numbers of the carbon atoms at which the substituents are located. If there are several substituents at a given atom, then the corresponding number in the name is repeated twice separated by a comma (2,2-). After the number, the number of substituents is indicated with a hyphen ( di- two, three- three, tetra- four, penta- five) and the name of the substituent (methyl, ethyl, propyl). Then, without spaces or hyphens, the name of the main chain. The main chain is called a hydrocarbon - a member of the homologous series of methane ( methane CH 4, ethane C 2 H 6, propane C 3 H 8, C 4 H 10, pentane C 5 H 12, hexane C 6 H 14, heptane C 7 H 16, octane C 8 H 18, nonan S 9 H 20, dean C 10 H 22).

Physical properties of alkanes

The first four representatives of the homologous series of methane are gases. The simplest of them is methane - a colorless, tasteless and odorless gas (the smell of “gas”, when you smell it, you need to call 04, is determined by the smell of mercaptans - sulfur-containing compounds specially added to methane used in household and industrial gas appliances so that people , located next to them, could detect the leak by smell).
Hydrocarbons of composition from C 4 H 12 to C 15 H 32 are liquids; heavier hydrocarbons - solids. The boiling and melting points of alkanes gradually increase with increasing carbon chain length. All hydrocarbons are poorly soluble in water; liquid hydrocarbons are common organic solvents.

Chemical properties of alkanes

Substitution reactions.
The most characteristic reactions for alkanes are free radical substitution reactions, during which a hydrogen atom is replaced by a halogen atom or some group. Let us present the equations characteristic reactions halogenation:

In case of excess halogen, chlorination can go further, up to the complete replacement of all hydrogen atoms with chlorine:

The resulting substances are widely used as solvents and starting materials in organic syntheses.
Dehydrogenation reaction(hydrogen abstraction).
During the passage of alkanes over the catalyst (Pt, Ni, Al 2 0 3, Cr 2 0 3) at high temperature(400-600 °C) a hydrogen molecule is eliminated and an alkene is formed:

Reactions accompanied by the destruction of the carbon chain.
All saturated hydrocarbons burn to form carbon dioxide and water. Gaseous hydrocarbons mixed with air in certain proportions can explode.
1. Combustion of saturated hydrocarbons is a free radical exothermic reaction that has a very great importance when using alkanes as fuel:

IN general view The combustion reaction of alkanes can be written as follows:

2. Thermal splitting of hydrocarbons.

The process occurs via a free radical mechanism. An increase in temperature leads to homolytic cleavage of the carbon-carbon bond and the formation of free radicals.

These radicals interact with each other, exchanging a hydrogen atom, to form an alkane molecule and an alkene molecule:

Thermal decomposition reactions underlie industrial process- cracking of hydrocarbons. This process is the most important stage of oil refining.

3. Pyrolysis. When methane is heated to a temperature of 1000 °C, methane pyrolysis begins - decomposition into simple substances:

When heated to a temperature of 1500 °C, the formation of acetylene is possible:

4. Isomerization. When linear hydrocarbons are heated with an isomerization catalyst (aluminum chloride), substances with a branched carbon skeleton are formed:

5. Aromatization. Alkanes with six or more carbon atoms in the chain cyclize in the presence of a catalyst to form benzene and its derivatives:

Alkanes enter into reactions that proceed according to the free radical mechanism, since all carbon atoms in alkane molecules are in a state of sp 3 hybridization. The molecules of these substances are built using covalent non-polar C-C(carbon - carbon) bonds and weakly polar C-H (carbon - hydrogen) bonds. They do not contain areas with increased or decreased electron density, easily polarized bonds, i.e., such bonds electron density in which it can shift under the influence external factors(electrostatic fields of ions). Consequently, alkanes will not react with charged particles, since the bonds in alkane molecules are not broken by the heterolytic mechanism.

Lecture outline

1. Nomenclature and isomerism.

2. Nomenclature.

3. Methods of obtaining.

4. Physical properties and structure.

5. Chemical properties.

6. Properties of covalent bonds.

7. Theory of molecular orbitals.

8. Hybridization.

9. Classification of organic reactions.

10. Classification of organic compounds.

1. Nomenclature and isomerism.

Definition : Organic compounds consisting of carbon and hydrogen atoms are called hydrocarbons.

Saturated hydrocarbons, alkanes, are organic compounds built from carbon and hydrogen atoms, in the molecules of which each carbon atom is connected to an adjacent carbon atom by no more than one bond (one valence). Valencies not spent on combining with carbon atoms are saturated with hydrogen. All carbon atoms are in the state sp 3 -hybridization.

Saturated hydrocarbons form a homologous series with the general formula C n H 2n+2. The founder of the homologous series of alkanes is methane. The first ten members of the homologous series of alkanes:

Methane, ethane, propane, butane, pentane, hexane. heptane, octane, nonane, decane .

A carbon atom in an alkane molecule connected to no more than one neighboring carbon atom is called primary. A carbon atom in an alkane molecule connected to no more than two neighboring carbon atoms is called secondary. A carbon atom in an alkane molecule connected to no more than three neighboring carbon atoms is called tertiary. A carbon atom in an alkane molecule connected to four neighboring carbon atoms is called quaternary.

Alkanes are characterized by structural isomerism. Starting with butane, the fourth member of the homologous series, several structures can correspond to one molecular formula:

Butane can have two isomers, pentane can have three, hexane can have five, etc. The number of isomers for any homologue can be calculated using the formula if the number of isomers in the previous member of the homologous series is known.

The structure of molecules of isomeric compounds can be represented as a carbon skeleton to which monovalent groups or residues of alkane molecules are attached. Such remains have a special name.

Definition : The remainder of an alkane molecule after the removal of a hydrogen atom is called a radical. IN in this case alkyl or alkyl radical.

Monovalent radicals are named after the parent alkane molecule. In this case, the suffix “an” of saturated hydrocarbons is replaced by “silt”. For example:

Depending on which atom carries the unpaired electron, primary, secondary and tertiary radicals are distinguished. An unbranched primary radical is called normal and is denoted by the lowercase letter “ n-».

The variety of structures of organic compounds is reflected by nomenclature - a naming system in which each name corresponds to only one compound.

2. Nomenclature.

There are three nomenclatures in organic chemistry. But each name must correspond.

1. Trivial nomenclature is a system of historically established names, but still used today. These names are given in early period developments in organic chemistry and do not reflect the structure of molecules. Examples of trivial names are the names of the first four members of the homologous series of alkanes.

2. The structure of molecules is taken into account by rational nomenclature. The name of an organic compound is based on the name of the first member of the homologous series. The remaining compounds are considered as its derivatives, in which the hydrogen atoms are replaced by alkyl radicals. For example:

Alkyl radicals are listed in order of increasing mass. The radical with a normal structure is older than the radical with an isomeric structure. If there is more than one substituting radical, then their number is indicated by prefixes di-three-tetra- .

As the number of compounds grew, the use of rational nomenclature became inconvenient, and chemists moved to consider no longer an atom or group of atoms, but a structure formed by a chain of carbon atoms.

3. Consideration of the largest chain is carried out in systematic nomenclature. The foundations of systematic nomenclature were laid at a congress of chemists in 1892 in Geneva. Which gave the basis for the name of the nomenclature - Geneva. The systematic nomenclature was improved at the congress in 1930 in Liege. The Liege nomenclature appeared. The modern version of the systematic nomenclature was adopted by the International Union of Pure and Applied Chemistry (IUPAC) in 1957. and improved in 1965.

In order to name an organic compound using systematic nomenclature it is necessary:

Select the longest (main) chain;

Determine the seniority of the groups;

Number the main chain, giving the highest group the lowest locant number;

List prefixes;

Give the full name of the connection.