Methyl ethyl drank. Alkanes - nomenclature, preparation, chemical properties. Chemical properties of alkanes

Hydrocarbons in whose molecules the atoms are connected by 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 to the corners of an equilateral triangular pyramid - a tetrahedron. The angles between the orbitals are 109° 28′.

Almost free rotation is possible around a single carbon-carbon bond, and alkane molecules can take on a wide variety of shapes with angles at the carbon atoms close to tetrahedral (109° 28′), for example, in the 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.

The absence of polar bonds in the molecules of saturated hydrocarbons 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 N 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 of 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).
When alkanes are passed over a catalyst (Pt, Ni, Al 2 0 3, Cr 2 0 3) at high temperatures (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, 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 the industrial process of hydrocarbon cracking. 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 nonpolar C-C (carbon-carbon) bonds and weakly polar C-H (carbon-hydrogen) bonds. They do not contain areas with increased or decreased electron density, or easily polarizable bonds, i.e., such bonds in which the electron density can shift under the influence of 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.

) are characterized by the suffix -an. The first four hydrocarbons bear historical names; starting from the fifth, the name of the hydrocarbon is based on the Greek name for the corresponding number of carbon atoms. Hydrocarbons in which all carbon atoms are arranged in one chain are called normal. Hydrocarbons with a normal chain of carbon atoms have the following names:

methane - CH 4 ethane - CH 3 -CH 3 propane - CH 3 -CH 2 -CH 3 butane - CH 3 -(CH 2) 2 -CH 3 pentane - CH 3 -(CH 2) 3 -CH 3 hexane - CH 3 -(CH 2) 4 -CH 3 heptane - CH 3 -(CH 2) 5 -CH 3 octane - CH 3 -(CH 2) 6 -CH 3 nonane - CH 3 -(CH 2) 7 -CH 3 decane -CH 3 -(CH 2) 8 -CH 3

The names of branched chain hydrocarbons are constructed as follows

1 . The name of this compound is based on the name of the hydrocarbon corresponding to the number of carbon atoms in the main chain:

The main chain of carbon atoms is considered to be the longest;
if two or more equally long chains can be distinguished in a hydrocarbon, then the main one is chosen as the one that has greatest number ramifications.

2 . After establishing the main chain, it is necessary to number the carbon atoms. Numbering begins from the end of the chain to which any of the alkyls is closest. If different alkyls are located at equal distances from both ends of the chain, then numbering begins from the end to which the radical with the smaller number of carbon atoms is closer (methyl, ethyl, propyl, etc.).

2,2,4-trimethylpent en

Wrong! Radicals are named in alphabetical order! 2.3 - If two or more side chains of different nature are present, they are cited in alphabetical order. (http://www.acdlabs.com/iupac/nomenclature/79/r79_36.htm) If identical radicals that determine the beginning of numbering are located at an equal distance from both ends of the chain, but on one side there are more of them than on another, then numbering starts from the end where the number of branches is greater.
When naming a compound, first list the substituents in alphabetical order (numerals are not taken into account), and before the name of the radical they put a number corresponding to the number of the carbon atom of the main chain at which this radical is located. After this, the hydrocarbon corresponding to the main chain of carbon atoms is named, separating the word from the numbers with a hyphen.

If a hydrocarbon contains several identical radicals, then their number is denoted by a Greek numeral (di, three, tetra, etc.) and placed before the name of these radicals, and their position is indicated, as usual, by numbers, with the numbers separated by commas, arranged in order their increases and are placed before the name of these radicals, separating them from it with a hyphen. For the simplest hydrocarbons of isostructure, their unsystematic names are retained ( isobutane, isopentane, neopentane, isohexane).

Radicals are named by replacing the suffix -an in the name of the hydrocarbon on -il:

methyl CH 3 - ethyl CH 3 -CH 2 - propyl CH 3 -CH 2 -CH 2 - butyl CH 3 -CH 2 -CH 2 -CH 2 - pentyl CH 3 -CH 2 -CH 2 -CH 2 -CH 2 -

Name amyl for the radical C 5 H 11 is no longer used.

When constructing the names of complex radicals, the numbering of their atoms begins from the carbon atom with free valency.
Divalent radicals are named by adding a suffix to the name of the hydrocarbon -ilene(except "methylene").

Sodium lauryl added to cosmetics, especially shampoos, to help the active ingredients penetrate the skin better. However, with prolonged use, it can accumulate in the skin and have a negative effect on the hair follicles. As a result, dandruff appears, hair becomes dry and split. May contribute to hair loss.

It is completely undesirable to use shampoos and foams with sodium lauryl for children: SLS penetrates the eyes, brain, heart, liver and remains there in high concentrations.

Manufacturers disguise their products with SLS as natural with the innocent phrase “derived from coconuts,” but this is precisely what should alert you.

Petrolatum

(petrolatum)

Even petrolatum- familiar, old, good - can harm our skin, since in fact it does not moisturize it - as is commonly believed, but causes dry skin and the appearance of cracks.

The reason lies in the fact that Vaseline (like other mineral oils) forms an impenetrable film on the skin - not releasing moisture, but also not allowing it to be received from the outside.

Glycerol

(Glycerin)

Glycerin is considered a natural skin moisturizer. Unfortunately, this only works if the air humidity is more than 65-70%.

In drier areas, glycerin - instead of taking moisture from the air - extracts moisture from cells that are located in the deeper layers of the skin. As a result, dry skin becomes even drier.

Bentonite

(Bentonite)

Bentonite is a natural mineral that can be found in face masks.

Bentonite grains sometimes have sharp edges, which causes micro-scratches on the skin. But the worst thing is that bentonite dries out the skin. Forming an impenetrable film, it prevents the natural respiration of the skin and the release of waste products, traps toxins and impurities. All this worsens the condition of the skin.

The question is, is such a face mask necessary?

Iazolidinyl-urea, imidazo-lidinyl-urea

(diazolidinyl urea, imidazolidinyl urea)

Iazolidinil used as a preservative. Releases formaldehyde, which has a toxic effect on the skin. If you are prone to allergies, it can cause contact dermatitis.

Other names: Germol II and Germol 115 (Germall II, Germall 115).

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When planning to purchase products designed to give health and beauty, do not be lazy to study their composition.

The longer the list of components of a cosmetic product, the more trust the manufacturer has. Three to five components most likely means that there are reasons not to indicate the entire composition.

It is most reasonable to give preference to cosmetic products that:

They are white in color, that is, they contain a minimum of dyes (like Avon products).
They have no smell. A faint fruity, floral or herbal aroma is allowed if the composition contains essential oils.
They do not foam at all or almost.

Such cosmetics contain less harm, will help avoid wrinkles and keep your skin young for as long as possible.

Reprinting or publication of articles on websites, forums, blogs, contact groups and mailing lists is permitted only if there is active link to the website .

The names of the first ten members of the series of saturated hydrocarbons have already been given. To emphasize that an alkane has a straight carbon chain, the word normal (n-) is often added to the name, for example: />

CH 3 -CH 2 -CH 2 -CH 3 CH 3 -CH 2 -CH 2 -CH 2 -CH 2 -C/>H 2/> -CH 3 />

n-butane n-heptane/>

(normal butane) (normal heptane)

When a hydrogen atom is removed from an alkane molecule, single-valent particles are formed called hydrocarbon radicals (abbreviated as R). The names of monovalent radicals are derived from the names of the corresponding hydrocarbons with the ending –an replaced by –yl. Here are relevant examples:

Hydrocarbons/>
		C/>6/>H/>14/>
		C/>7/>H/>16/>
		C/>8/>H/>18/>
	C/>4/>H/>10/>	C/>9/>H/>20/>
	C/>5/>H/>12/>	C/>10/>H/>22/>
Monovalent radicals/>
		C/>6/>H/>13/> –/>
	C/>2/>H/>5/> – />	C/>7/>H/>15/> –/>
	C/>3/>H/>7/> – />	C/>8/>H/>17/> –/>
	C/> 4/> H/> 9/> –/>	C/> 9/> H/> 19/> –/>
Pentyl />(amyl)/>	C/>5/>H/>11/> –/>	C/>10/>H/>21/> –/>

Radicals are formed not only by organic, but also by inorganic compounds. So, if from nitric acid subtract the hydroxyl group OH, you get a monovalent radical - NO 2, called a nitro group, etc./>

When two hydrogen atoms are removed from a hydrocarbon molecule, divalent radicals are obtained. Their names are also derived from the names of the corresponding saturated hydrocarbons with the ending -ane replaced by -ylidene (if the hydrogen atoms are separated from one carbon atom) or -ylene (if the hydrogen atoms are removed from two adjacent carbon atoms). The radical CH 2 = is called methylene.

The names of radicals are used in the nomenclature of many hydrocarbon derivatives. For example: CH 3 I/> - methyl iodide, C 4 H 9 Cl/> -butyl chloride, CH 2 Cl/> 2/> - methylene chloride, C 2 H 4 B/>r/> 2/> - ethylene bromide (if bromine atoms are bonded to different carbon atoms) or ethylidene bromide (if bromine atoms are bonded to one carbon atom)./>

To name isomers, two nomenclatures are widely used: old - rational and modern - substitutive, which is also called systematic or international (proposed by the International Union of Pure and Applied Chemistry IUPAC)./>

According to rational nomenclature, hydrocarbons are considered to be derivatives of methane, in which one or more hydrogen atoms are replaced by radicals. If the same radicals are repeated several times in a formula, then they are indicated by Greek numerals: di - two, three - three, tetra - four, penta - five, hexa - six, etc. For example:

Rational nomenclature is convenient for not very complex connections./>

According to substitutive nomenclature, the name is based on one carbon chain, and all other fragments of the molecule are considered as substituents. In this case, the longest chain of carbon atoms is selected and the atoms of the chain are numbered from the end to which the hydrocarbon radical is closest. Then they call: 1) the number of the carbon atom to which the radical is associated (starting with the simplest radical); 2) a hydrocarbon that has a long chain. If the formula contains several identical radicals, then before their names indicate the number in words (di-, tri-, tetra-, etc.), and the numbers of the radicals are separated by commas. This is how hexane isomers should be called according to this nomenclature:/>

Here's a more complex example:

Both substitutive and rational nomenclature are used not only for hydrocarbons, but also for other classes organic compounds. For some organic compounds, historically established (empirical) or so-called trivial names are used (formic acid, sulfuric ether, urea, etc.).

When writing the formulas of isomers, it is easy to notice that the carbon atoms occupy different positions in them. A carbon atom that is bonded to only one carbon atom in the chain is called primary, to two is called secondary, to three is tertiary, and to four is quaternary. So, for example, in the last example, carbon atoms 1 and 7 are primary, 4 and 6 are secondary, 2 and 3 are tertiary, 5 is quaternary. The properties of hydrogen atoms, other atoms, and functional groups depend on whether they are bonded to a primary, secondary, or tertiary carbon atom. This must always be taken into account./>

Methyl ethyl drank. Alkanes - nomenclature, preparation, chemical properties. Chemical properties of alkanes

Homologous series of methane

Isomerism and nomenclature

Nomenclature Basics

Physical properties of alkanes

Chemical properties of alkanes

The names of branched chain hydrocarbons are constructed as follows

see also

See what "Systematic nomenclature of alkanes" is in other dictionaries:

Methyl, propyl, butyl and ethyl parabens

Propylene glycol

Diethanolamine, triethanolamine

Sodium lauryl sulfate

Petrolatum

Glycerol

Bentonite

Iazolidinyl-urea, imidazo-lidinyl-urea

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