1.1 ALKANE (saturated hydrocarbons).
1.2 METHODS FOR OBTAINING ALKANES.
1.3 ALKANE REPRESENTATIVES.
2.1 ALKENES (ethylene hydrocarbons).
2.2 METHODS FOR OBTAINING ALKENES.
2.3 REPRESENTATIVES OF ALKENES.
3.1 ALKYNES (acetylenic hydrocarbons).
3.2 METHODS FOR OBTAINING ALKYNES.
3.3 REPRESENTATIVES OF ALKYNES.
4. APPLICATION OF ALKANE, ALKENES, ALKYNES.
1.1 LIMITED HYDROCARBONS (alkanes).
Saturated hydrocarbons (alkanes) are compounds consisting of carbon and hydrogen atoms, interconnected only by Q-bonds, and not containing cycles. In alkanes, carbon atoms are in the degree of sp3 hybridization.
1.2 Methods for obtaining alkanes.
The main natural source of saturated hydrocarbons is oil, and for the first members of the homologous series, natural gas. However, the isolation of individual compounds from oil or its cracking products is a very laborious and often impossible task, so one has to resort to synthetic methods of production.
1. Alkanes are formed by the action of metallic sodium on monohalogen derivatives - the Wurtz reaction:
H3C-CH2-Br + Br-CH2-CH3 CH3-CH2-CH2-CH3 + 2NaBr
If different halogen derivatives are taken, then a mixture of three different alkanes is formed, since the probability of meeting identical or different molecules in the reaction complex is equal, and their reactivity is close:
3C2H5I + 3CH3CH2CH2IC4H10 + C5H12 + C6H14 + 6NaI
2. Alkanes can be obtained by reducing alkenes or alkynes with hydrogen in the presence of catalysts:
NzS-CH \u003d CH-CHz NzS-CH2-CH2-CH3
3. A wide variety of alkane derivatives can be reduced at high temperature with hydroiodic acid:
H3C H3C
CHBr +2HI CH2 + HBr + I2
H3C H3C
However, in these cases, partial isomerization of the carbon skeleton is sometimes observed - more branched alkanes are formed.
4. Alkanes can be obtained by fusing salts of carboxylic acids with alkali. The resulting alkane contains one carbon atom less than the original carboxylic acid:
O
CH3-C + NaOH CH4 + Na2C03
ONa
1.3 Representatives of alkanes
According to the theory of structure of A. M. Butlerov, the physical properties of substances depend on their composition and structure. Consider, using the example of saturated hydrocarbons, the change in physical properties in the homologous series.
The first four members of the homologous series, starting with methane, are gaseous substances. From pentane upwards, normal hydrocarbons are liquids. Methane condenses into a liquid only at -162 °C. In subsequent members of the series, the boiling point increases, and when going to the next homologue, it increases by approximately 25 °.
The density of hydrocarbons at the boiling point for the lower members of the series increases first rapidly, and then more slowly: from 0.416 for methane to a value slightly greater than 0.78. The melting point of normal hydrocarbons in the homologous series increases slowly. Starting with the hydrocarbon C16H34, the highest homologues at ordinary temperature are solid substances.
The boiling point of all branched alkanes is lower than that of normal alkanes, and, moreover, the lower the more branched the carbon chain of the molecule. This can be seen, for example, from a comparison of the boiling points of three isomeric pentanes. Conversely, the melting point is highest for the isomers with the most branched carbon chain. Thus, of all the isomeric octanes, only the hexa-methyl stage (CH3)3C-C (CH3)3 is a solid even at ordinary temperature (mp 104°C). These patterns are explained by the following reasons.
The transformation of a liquid into a gas is prevented by van der Waals forces of interaction between the atoms of individual molecules. Therefore, the more atoms in the molecule, the higher the boiling point of the substance, therefore, in the homologous series, the boiling point should increase evenly. If we compare the interaction forces of n-pentane and neopentane molecules, it is clear that these forces are greater for a molecule with a normal chain of carbon atoms than for branched ones, since in a neopentane molecule the central atom is generally excluded from the interaction.
The main factor affecting the melting point of a substance is the packing density of the molecule in the crystal lattice. The more symmetrical the molecule, the denser its packing in the crystal and the higher the melting point (for n-pentane -132° C, for neopentane -20° C)
2.1 ALKENES (ethylene hydrocarbons, olefins)
Hydrocarbons, in the molecule of which, in addition to simple carbon-carbon and carbon-hydrogen Q-bonds, there are carbon-carbon
-bonds are called unlimited. Since the formation of a -bond is formally equivalent to the loss of two hydrogen atoms by a molecule, unsaturated hydrocarbons contain 2n less hydrogen atoms than the limiting ones, where n is the number of -bonds
C6H14 C6H12C6H10C6H8C6H6
A series whose members differ from each other by (2H)n is called an isological series. Thus, in the scheme above, the isologues are hexane, hexenes, hexadienes, hexines, hexatrienes, and benzene.
Hydrocarbons containing one bond (i.e., a double bond) are called alkenes (olefins) or, according to the first member of the series, ethylene, ethylene hydrocarbons. The general formula for their homologous series is CnH2n
2.2 Methods for obtaining alkenes
Under the action of alcoholic solutions of caustic alkalis on halogen derivatives: hydrogen halide is split off and a double bond is formed:
H3C-CH2-CH2BrH3C-CH=CH2+NaBr+H2O
Propyl bromide Propylene
If there are tertiary, secondary and primary hydrogen atoms in the α-position to the carbon atom bonded to the halogen, then the tertiary hydrogen atom is predominantly split off, to a lesser extent secondary and even more so primary (Zaitsev's rule):
H3C-C-CI H3C-C + KCL + H2O
H3C CH3 H3C CH3
2,3-Dimethyl-3-chloropentane 2,3-Dimethylpentene-2
This is due to the thermodynamic stability of the resulting alkenes. The more substituents an alkene has on the vinyl carbon atoms, the higher its stability.
2. The effect of water-removing agents on alcohols: a) when alcohols are passed over aluminum oxide at 300-400 ° C.
NzS-CH-CH2.-CHzNzS-CH \u003d CH-CH3
OH Butene-2
sec-butyl alcohol
B) when sulfuric acid acts on alcohols under mild conditions, the reaction proceeds through the intermediate formation of sulfuric acid esters:
H3C-CH-CH3 H3C-CH-CH3 H3C-CH=CH2
OH O-SO3H
isopropyl alcohol
During the dehydration of alcohols under harsh conditions in acidic media, the same pattern is observed in the elimination of hydrogen atoms of various types, as in the elimination of hydrogen halide.
The first stage of this process is the protonation of alcohol, after which a water molecule is split off and a carbocation is formed:
CH3-CH2-CH-CH3 + H CH3-CH2-CH-CH3 CH3-CH-CH-
OHOH
H H
CH3CH3-CH-CH-CH3CH3-CH=CH-CH3
The resulting carbocation is stabilized by the ejection of a proton from a neighboring position with the formation of a double bond (β-elimination). In this case, the most branched alkene is also formed (thermodynamically more stable). During this process, rearrangements of carbocations associated with the isomerization of the carbon skeleton are often observed:
CH3 CH3
CH3 C-CH – CH3 CH3 C-CH-CH3
CH3 OH CH3
CH3 CH3 CH3 CH3
C-CH C=C
CH3 CH3 CH3 CH3
3. Under the action of Zn or Mg on dihalogen derivatives with two
halogen atoms at neighboring carbon atoms:
H3C – C CH2CIH3C - C - CH2+MgCI2
CH3 CH3
1,2-dichloro-2-metal-isobutylene
propane
4. Hydrogenation of acetylenic hydrocarbons over catalysts with reduced activity (Fe or “poisoned”, i.e., treated with sulfur-containing compounds to reduce catalytic activity, Pt and Pd):
HCC-CH(CH3)2H2C=CH-CH(CH3)2
2.3 Representatives of alkenes.
Like alkaii, the lower homologues of a number of the simplest alkenes under normal conditions are gases, and starting from C5 they are low-boiling liquids (see table).
M.p., T. d4
Formula Name °C Bip, °C
Ch2=CH2 Ethylene -169 -104 0.5660 (at -102°C)
CH3CH \u003d CH3 Propylene -185 -47 0.6090 (at -47 "C)
CH3CH3CH=CH2 CH3-CH=CH-CH3 (cis) Butene-1 -130 -5 0.6696 (at -5°C) 0.6352 (at O°C)
-139 +4
(cis)
CH3-CH=CH-CH3 (trans)-Butep-2 -105 +1 0.6361 (at 0°C)
(trance)
(CH3)3C=CH2 Ieobutylene -140 -7 0.6407 (at 0°C)
All alkenes, like alkanes, are practically insoluble in water and readily soluble in other organic solvents, with the exception of methyl alcohol; they all have a lower density than water.
3.1 ALKYNES (acetylenic hydrocarbons)
Alkynes are hydrocarbons containing, in addition to Q-bonds, two
-bonds (triple bond) on one pair of carbon atoms. The general formula of the homologous series of acetylenic hydrocarbons is СnН2n-2. The formation of one bond is formally equivalent to the loss of two hydrogen atoms.
It has been proved by various physical methods that acetylene C2H2 - I is the simplest representative of the homologous series of alkynes - has a linear molecule in which the length of the carbon-carbon triple bond is 1.20 A, and the length of carbon-hydrogen bonds is 1.06 A.
The CH bonds in acetylene are among the Q bonds formed by overlapping the s orbital of hydrogen with the hybridized sp orbital of carbon; the molecule has one carbon-carbon a-bond (formed by the overlap of two hybridized sp-orbitals of carbon) and two carbon-carbon bonds - the result of the overlap of two mutually perpendicular pairs of "pure" p-orbitals (P and P) of neighboring carbon atoms. The bond angles in acetylene, based on this model, are 180° and the molecule has a linear conformation, which makes cis-trans isomerism impossible with a triple bond.
3.2 Methods for obtaining alkynes.
The most common way to obtain acetylenic hydrocarbons is the action of an alcoholic solution of alkalis on dihalo derivatives of saturated hydrocarbons with a vicinal (a) or geminal (b) arrangement of halogen atoms
a) CH2Br –CH2Br -> CHCH + 2HBr
b) CH3-CH2-CHCl2 -> CH3-CCH+2ISl
CH3-CH2-CCl2-CH3 -> CH3-C C-CH3 + 2HC1
Since vicinal dihalogen derivatives are usually obtained by the addition of halogens to ethylene hydrocarbons, reaction (a) can be considered as a reaction for the conversion of ethylene hydrocarbons into acetylenic ones.
Geminal dihalogen derivatives (both halogen atoms on one carbon atom) are derivatives of ketones or aldehydes and, therefore, using reactions (b), it is possible to make the transition from carbonyl compounds to alkynes. When splitting off hydrogen halides, the already known Zaitsev rule applies that hydrogen is split off from a carbon atom containing a smaller number of hydrogen atoms.
Acetylene can be obtained directly from high-temperature cracking (thermal or electrothermal) of methane or more complex hydrocarbons:
2SN4N-SS-N + ZN2
3.3 Representatives of alkynes.
As with alkanes and alkenes, the lower members of the homologous series of alkynes under normal conditions are gaseous substances. Table data. 22 show that the main physicochemical characteristics of hydrocarbons of the considered classes differ little from each other (see table).
Formula Name Melting point, °С Boiling point, °С D4
HCCHCH3CCHHCC- CH2CH3 CH3CCCH3 Acetylene PropynButyn-1Butyn-2 -82-105-137-33 -84(sub-23) 927 0.6200 (at -84°C) 0.6785 (at -27°C) 0;669b (at -10°C) 0.6880 (at 25°C)
4. APPLICATIONS OF ALKANE, ALKYNE, ALKENES
Alkenes, together with alkanes, acetylene, and aromatic hydrocarbons, are one of the main raw materials for the heavy (large-tonnage) organic synthesis industry.
Ethylene is used in huge quantities for processing into polyethylene and ethyl alcohol, it goes for processing into ethylene glycol and is used in greenhouses to accelerate the ripening of fruits.
Propylene is processed into polypropylene, acetone, isopropyl alcohol.
Acetylene plays an extremely important role in industry. Its world production reaches several million tons. A huge amount of acetylene is used for welding metals, when it burns
in oxygen, the temperature reaches 2800 ° C. This is a significantly higher temperature than the combustion of hydrogen in oxygen, not to mention the combustion of methane. The reason for this is the much lower heat capacity of CO2 compared to H2O, which is formed more during the combustion of alkanes than alkynes:
2СзН6 + 7O2 -> 4СО2 + 6Н2О
2C2 H2 + 5O2 -> 4CO2 + 3H2O
The unpleasant smell of acetylene obtained from carbide is due to impurities of PH3 and AsH3, pure acetylene smells like all lower hydrocarbons (gasoline). Acetylene and its mixtures with air are highly explosive; acetylene is stored and transported in cylinders in the form of acetone solutions impregnating porous materials.
OIL AND ITS REFINING
Oil composition. The main natural source of saturated hydrocarbons is oil. The composition of oils varies depending on the field, but all oils are usually separated into the following fractions during simple distillation: gas fraction, gasoline, jet fuel, kerosene, diesel fuel, paraffin, oil tar.
The gas fraction (bp. up to 40? C) contains normal and branched alkanes up to C, mainly propane and butanes. Natural gas from gas fields consists mainly of methane and ethane.
Aviation gasoline (bp. 40-180 ° C) contains hydrocarbons C6 - C10 More than 100 individual compounds have been found in gasoline, including normal and branched alkanes, cycloalkanes and alkylbenzenes (arenes).
Jet fuel (bp 150-280°C).
Tractor kerosene (t, bp 110-300 °C) contains C7-C14 hydrocarbons.
Diesel fuel (bp 200-330 °C), which contains hydrocarbons C13 - C18, is cracked on a large scale, turning into alkanes (and alkenes) with a lower molecular weight (see below).
Lubricating oils (bp 340-400°C) contain hydrocarbons C18 - C25.
Petroleum paraffin (bp. 320-500 ° C), it contains hydrocarbons C26-C38, from which vaseline is isolated. The residue after distillation is commonly referred to as asphalt or tar.
In addition to hydrocarbons of various classes, oil contains oxygen, sulfur and nitrogen-containing substances; sometimes their total content reaches several percent.
Currently, the most recognized theory is the organic origin of oil as a product of the transformation of plant and animal residues. This is confirmed by the fact that porphyrin residues, steroids of plant and animal origin, and the so-called "chemofossils" - the most diverse fragments contained in plankton - were found in oil samples.
Although it is generally recognized that oil is the most valuable natural source of chemical raw materials, the main amount of oil and oil products is still burned in internal combustion engines (gasoline), diesel engines and jet engines (kerosene).
motor fuel. Octane number. Gasolines of various origins behave differently in internal combustion engines.
In an effort to maximize engine power with small dimensions and weight, they try to increase the compression ratio of the combustible mixture in the cylinder. However, in high-speed four-stroke engines operating with forced ignition, this sometimes causes pre-ignition of the mixture - detonation. This reduces the power of the motor and accelerates its wear. This phenomenon is associated with the composition of liquid fuel, since hydrocarbons of different structures behave differently when used as a motor fuel. The worst performance - in paraffins of normal structure.
Normal heptane was adopted as the standard for a combustible substance with a high detonation ability. The more branched the carbon chain of the paraffinic hydrocarbon, the better its combustion in the cylinder proceeds and the greater the degree of compression of the combustible mixture can be achieved. 2, 2, 4-trimethylpentane (commonly referred to as isooctane) with good anti-knock properties has been adopted as a motor fuel standard. Composing mixtures of this octane with n-heptap in various proportions, their behavior in the engine is compared with the behavior of the tested gasoline. If a mixture containing 70% isooctane behaves in the same way as the gasoline under study, then the latter is said to have an octane number of 70 (the octane number of isooctane is taken as 100; the octane number of n-heptane is taken to be zero).
One of the ways to increase the knock resistance of fuels for engines with spark ignition is the use of antiknock agents.
Antiknock agents are substances that are added to gasolines (not more than 0.5%) to improve antidetonation properties. A sufficiently effective antiknock agent is tetraethyl lead (TES) Pb (C2H5)4
However, gasoline from thermal power plants and its combustion products are very toxic. At present, new antiknock agents based on organic manganese compounds of the type cyclopentadieneiclpsntacarbonyl manganese C5H5Mn (CO)5 have been found: they are less toxic and have better antiknock properties. The addition of these anti-knock agents to good grades of gasoline produces fuel with an octane rating of up to 135.
For rocket and diesel engines, on the contrary, fuels with a normal chain of carbon atoms, which have the lowest ignition temperature, are most valuable. This characteristic is taken
evaluate in cetane numbers. The cetane number 100 has the hydrocarbon n-Sc, Hd4, and the cetane number 0 has 1-methylnaphthalene.
Synthesis of hydrocarbons from CO+H2. By passing a mixture of carbon monoxide (II) and hydrogen over finely crushed nickel at 250 ° C, methane can be obtained:
CO+3H2CH4+H2O
If this reaction is carried out at a pressure of 100-200 atm and a temperature of up to 400 ° C, a mixture is obtained, consisting mainly of oxygen-containing products, among which alcohols predominate; this mixture was called schshpol.
When using iron-cobalt catalysts and a temperature of 200 ° C, a mixture of alkanes is formed - syntin.
nCO + (2n + 1) H2 CnH2n + 2 + H2O
Sintin and synthol are products of large-scale organic synthesis and are widely used as raw materials for many chemical industries.
Clathrates. Sintin and gasoline fractions of oil consist of mixtures of hydrocarbons with a normal structure and branched chains. Recently, an effective method has been found for the separation of organic compounds with normal chains and branched ones, which in the general case has received the name of the clathrate separation method. Urea was used to separate hydrocarbons. Urea crystals are built in such a way that there are narrow hexagonal channels inside the crystals. The diameter of these channels is such that only normal hydrocarbons can pass through and be retained by adsorption forces. Therefore, when a mixture of organic compounds is treated with urea (or some other compounds), substances with a normal chain of carbon atoms crystallize together with it in the form of complexes. This method certainly has a very great future - when a greater number of effective clathrate formers are found.
Ministry of Education R.F.
Kursk state agricultural
academy. Prof. I. I. Ivanova
ABSTRACT ON
organic chemistry
OBTAINING ALKANES, ALKENES, ALKYNS.
KEY REPRESENTATIVES.
APPLICATION IN INDUSTRY.
Completed:
KURSK-2001
Plan.
1.1 ALKANE (saturated hydrocarbons).
1.2 METHODS FOR OBTAINING ALKANES.
1.3 ALKANE REPRESENTATIVES.
2.1 ALKENES (ethylene hydrocarbons).
2.2 METHODS FOR OBTAINING ALKENES.
2.3 REPRESENTATIVES OF ALKENES.
3.1 ALKYNES (acetylenic hydrocarbons).
3.2 METHODS FOR OBTAINING ALKYNES.
3.3 REPRESENTATIVES OF ALKYNES.
4. APPLICATION OF ALKANE, ALKENES, ALKYNES.
1.1 LIMITED HYDROCARBONS (alkanes).
Saturated hydrocarbons (alkanes) are compounds consisting of atoms
carbon and hydrogen, interconnected only by Q-bonds, and not containing
cycles. In alkanes, carbon atoms are in the degree of hybridization sp3.
1.2 Methods for obtaining alkanes.
The main natural source of saturated hydrocarbons is oil, and for
the first members of the homologous series are natural gas. However, selection
individual compounds from oil or its cracking products are very
time-consuming, and often impossible task, so you have to resort to
synthetic methods of obtaining.
1. Alkanes are formed under the action of metallic sodium on
monohalogen derivatives - wurtz reaction:
H3C-CH2-Br + Br-CH2-CH3 CH3-CH2-CH2-CH3 + 2NaBr
If different halogen derivatives are taken, then a mixture of three different
alkanes, since the probability of meeting molecules in the reaction complex
identical or different is equal, and their reactivity is close:
3C2H5I + 3CH3CH2CH2IC4H10 + C5H12 + C6H14 + 6NaI
2. Alkanes can be obtained in the reduction of alkenes or alkynes
hydrogen in the presence of catalysts:
NzS-CH \u003d CH-CHz NzS-CH2-CH2-CH3
3. A wide variety of alkane derivatives can be restored at
high temperature hydroiodic acid:
CHBr +2HI CH2 + HBr + I2
However, in these cases, partial isomerization of the carbon
skeleton - more branched alkanes are formed.
4. Alkanes can be obtained when fusing salts of carboxylic acids with
alkali. The resulting alkane contains one less carbon atom,
than the original carboxylic acid:
CH3-C + NaOH CH4 + Na2C03
1.3 Representatives of alkanes
According to the theory of structure of A. M. Butlerov, the physical properties of substances depend
on their composition and structure. Consider the example of saturated hydrocarbons
change in physical properties in the homologous series.
The first four members of the homologous series, starting with methane, are gaseous
substances. From pentane and up, normal hydrocarbons are
a liquid. Methane condenses into a liquid only at -162 °C. Subsequent
members of the series, the boiling point increases, and upon transition to the next
to the homologue, it increases by approximately 25°.
The density of hydrocarbons at the boiling point for the lower members of the series
increases rapidly at first, and then more slowly: from 0.416 for methane to
values slightly greater than 0.78. The melting point of normal
hydrocarbons in the homologous series increases slowly. Beginning with
hydrocarbon С16Н34, higher homologues at ordinary temperature - substances
The boiling point of all branched alkanes is lower than that of normal
alkanes, and, moreover, the lower, the more branched the carbon chain of the molecule.
This can be seen, for example, from a comparison of the boiling points of three isomeric pentanes.
Conversely, the melting point is highest for isomers with
the most branched carbon chain. So, from all isomeric octane
only the hexa-methyl stage (CH3)3C-C (CH3)3 is a solid even at
normal temperature (mp. 104 ° C). These patterns are explained
the following reasons.
The transformation of a liquid into a gas is prevented by van der Waals interaction forces
between the atoms of individual molecules. Therefore, the more atoms in a molecule, the higher
the boiling point of a substance, therefore, in the homologous series, the temperature
boiling should increase evenly. If we compare the forces of interaction of molecules
n-pentane and neopentane, it is clear that these forces are greater for a molecule with
a normal chain of carbon atoms than for branched ones, since in a molecule
neopentane, the central atom is generally excluded from the interaction.
Density is the main factor affecting the melting point of a substance.
packing of a molecule in a crystal lattice. The more symmetrical the molecule, the
the denser its packing in the crystal and the higher the melting point (at n
Pentane -132° C, neopentane -20° C)
2.1 ALKENES (ethylene hydrocarbons, olefins)
Hydrocarbons, in the molecule of which, in addition to simple Q-bonds, carbon - carbon and
carbon - hydrogen there are carbon-carbon
The connections are called
unlimited. Since education is
bond is formally equivalent to the loss of two hydrogen atoms by the molecule, then
unsaturated hydrocarbons contain 2p fewer hydrogen atoms than
limit, where n is a number
C6H14 C6H12C6H10C6H8C6H6
A series whose members differ from each other by (2Н)n is called
isological side. So, in the above scheme, the isologists are
hexane, hexenes, hexadienes, hexines, hexatrienes and benzene.
hydrocarbons containing one
A bond (i.e. a double bond) is called alkenes (olefins) or, by
the first member of the series - ethylene, ethylene hydrocarbons. General formula
their homologous series - CnH2n
2.2 Methods for obtaining alkenes
Under the action of alcoholic solutions of caustic alkalis on halogen derivatives:
hydrogen halide is cleaved off and a double bond is formed:
H3C-CH2-CH2BrH3C-CH=CH2+NaBr+H2O
Propyl bromide Propylene
If in the α-position to the carbon atom bonded to the halogen is
tertiary, secondary and primary hydrogen atoms, then it is predominantly split off
tertiary hydrogen atom, to a lesser extent secondary and even more so primary
(Zaitsev's rule):
H3C-C-CI H3C-C + KCL + H2O
2,3-Dimethyl-3-chloropentane 2,3-Dimethylpentene-2
This is due to the thermodynamic stability of the resulting alkenes. How
the more substituents an alkene has on vinyl carbon atoms, the higher its
sustainability.
2. Action on alcohols of water-removing agents: a) when passing
alcohols over aluminum oxide at 300-400°C.
NzS-CH-CH2.-CHzNzS-CH \u003d CH-CH3
Deut-butyl alcohol
b) when sulfuric acid acts on alcohols under mild conditions, the reaction proceeds
through the intermediate formation of sulfuric acid esters:
H3C-CH-CH3 H3C-CH-CH3 H3C-CH=CH2
isopropyl alcohol
During the dehydration of alcohols under severe conditions in acidic media, the same
regularity in the splitting off of hydrogen atoms of various types, as in
elimination of hydrogen halide.
The first stage of this process is the protonation of alcohol, after which
a water molecule is split off and a carbocation is formed:
CH3-CH2-CH-CH3 + H CH3-CH2-CH-CH3 CH3-CH-CH-
CH3CH3-CH-CH-CH3CH3-CH=CH-CH3
The resulting carbocation is stabilized by the ejection of a proton from the neighboring
positions with the formation of a double bond (β-elimination). In that
case, the most branched alkene is also formed (thermodynamically more
stable). During this process, rearrangements of carbocations are often observed.
associated with the isomerization of the carbon skeleton:
CH3 C-CH – CH3 CH3 C-CH-CH3
CH3 CH3 CH3 CH3
3. Under the action of Zn or Mg on dihalogen derivatives with two
halogen atoms at neighboring carbon atoms:
H3C – C CH2CIH3C - C - CH2+MgCI2
1,2-dichloro-2-metal-isobutylene
4. Hydrogenation of acetylenic hydrocarbons over catalysts with
reduced activity (Fe or "poisoned", i.e. processed
HCC-CH(CH3)2H2C=CH-CH(CH3)2
2.3 Representatives of alkenes.
Like alkaii, the lower homologues of a number of the simplest alkenes under normal conditions are
gases, and starting from C5 - low-boiling liquids (see table).
| m.p., | T. | d4 | ||
| Formula | Name | °С | Kip., °С | |
| Ch2=CH2 | Ethylene | -169 | -104 | 0.5660 (at -102°C) |
| CH3CH=CH3 | Propylene | -185 | -47 | 0.6090 (at -47 "C) |
| CH3CH3CH=CH2 CH3-CH=CH-CH3 | (cis)Butene-1 | -130 | -5 | 0.6696 (at -5°C) 0.6352 (at O°C) |
| -139 | +4 | |||
(cis) | ||||
| CH3-CH=CH-CH3 | (trans)-Butep-2 | -105 | +1 | 0.6361 (at 0°C) |
(trance) | ||||
| (CH3)3C=CH2 | iobutylene | -140 | -7 | 0.6407 (at 0°C) |
All alkenes, like alkanes, are practically insoluble in water and readily soluble.
in other organic solvents, with the exception of methyl alcohol; all
they have a lower density than water.
3.1 ALKYNES (acetylenic hydrocarbons)
Alkynes are hydrocarbons containing, in addition to Q-bonds, two
Ties (triple
bond) on one pair of carbon atoms. General formula of the homologous series
acetylenic hydrocarbons СnН2n-2 formation of one
A bond is formally equivalent to the loss of two hydrogen atoms.
It has been proven by various physical methods that acetylene C2H2 - I is the simplest
representative of the homologous series of alkynes - has a linear molecule,
in which the length of the carbon-carbon triple bond is 1.20 A, and the bond length
carbon-hydrogen 1.06 A.
The C-H bonds in acetylene are among the Q-bonds formed by
overlapping of the hydrogen s-orbital with the hybridized sp- orbital
carbon; there is one carbon-carbon a-bond in the molecule (formed by
overlap of two hybridized sp-orbi- carbon hoists) and two
carbon-carbon
Connections are the result of overlapping of two mutually perpendicular pairs of "pure"
p-orbitals (R
neighboring carbon atoms. Bond angles in acetylene based on this model
are equal to 180° and the molecule has a linear conformation, which makes it impossible
cis-trans isomerism at the triple bond.
3.2 Methods for obtaining alkynes.
The most common way to obtain acetylenic hydrocarbons is
the effect of an alcoholic solution of alkalis on dihalogen derivatives of limiting
hydrocarbons with vicinal (a) or geminal (b) arrangement of atoms
halogen
a) CH2Br -CH2Br -> SNSN + 2НВг
b) CH3-CH2-CHCl2 -> СНЗ-ССН + 2ISl
CH3-CH2-CCl2-CH3 -> CH3-C C-CH3 + 2HC1
Since vicinal dihalogen derivatives are usually obtained by adding
halogens to ethylene hydrocarbons, then reaction (a) can be considered as
the reaction of converting ethylene hydrocarbons into acetylenic ones.
Geminal dihalogen derivatives (both halogens on one carbon atom)
are derivatives of ketones or aldehydes and, therefore, with the help of
reactions (b) it is possible to carry out the transition from carbonyl compounds to alkynes.
When splitting off hydrogen halides, the already known Zaitsev rule applies, which
hydrogen is split off from a carbon atom containing a smaller amount
hydrogen atoms.
Acetylene can be obtained directly from high-temperature cracking
(thermal or electrothermal) methane or more, complex
hydrocarbons:
2SN4N-SS-N + ZN2
3.3 Representatives of alkynes.
As with alkanes and alkenes, the lower members of the homologous series of alkynes in ordinary
gaseous conditions. Table data. 22 show that the main
physical and chemical characteristics of hydrocarbons of the considered classes are few
differ from each other (see table).
| Formula | Name | T. pl., °С | T boil., ° С | D4 |
HCC-CH2CH3 CH3CCCH3 | Acetylene Propyne | (air,-23) 9 | 0.6200 (at -84°C) 0.6785 (at -27°C) 0;669b (at -10°C) 0.6880 (at 25°C) | |
4. APPLICATIONS OF ALKANE, ALKYNE, ALKENES
Alkenes along with alkanes, acetylene and aromatic hydrocarbons
are one of the main raw material sources of heavy industry
(multi-tonnage) organic synthesis.
Ethylene is used in large quantities for processing into polyethylene and
ethyl alcohol, it goes for processing into ethylene glycol and is used in
greenhouses to accelerate the ripening of fruits.
Propylene is processed into polypropylene, acetone, isopropyl alcohol.
Acetylene plays an extremely important role in industry. His world
production reaches several million tons. Huge amount
acetylene is used to weld metals, when it burns
in oxygen, the temperature reaches 2800 ° C. This is a much higher
temperature than the combustion of hydrogen in oxygen, not to mention the combustion
methane. The reason for this is the much lower heat capacity of CO2 compared to
H2O, which is formed more during the combustion of alkanes than alkynes:
2СзН6 + 7O2 -> 4CO2 + 6H2O
2C2 H2 + 5O2 -> 4CO2 + ZH2O
The unpleasant odor of carbide-derived acetylene is due to PH3 impurities.
and AsH3, pure acetylene smells like all lower hydrocarbons (gasoline).
Acetylene and its mixtures with air are highly explosive; acetylene is stored and
transported in cylinders in the form of acetone solutions impregnating
porous materials.
OIL AND ITS REFINING
Oil composition. The main natural source of saturated hydrocarbons
is oil. The composition of oils varies depending on the field,
however, all oils in simple distillation are usually separated into the following fractions:
gas fraction, gasoline, jet fuel, kerosene, diesel fuel,
paraffin, oil tar.
gas fraction(bp. up to 40◦C) contains normal and
branched alkanes up to C, mainly propane and butanes. natural gas from
gas fields consists mainly of methane and ethane.
Aviation gasoline(bp. 40-180 ° C) contains hydrocarbons
C6 - C10 More than 100 individual compounds have been found in gasoline,
which include straight and branched alkanes, cycloalkanes and
alkylbenzenes (arenes).
jet fuel(bp 150-280°C).
Tractor kerosene(t, bp 110-300 °C) contains C7-C14 hydrocarbons.
Diesel fuel(bp. 200-330 ° C), which includes
hydrocarbons C13 - C18, are cracked on a large scale, turning
into alkanes (and alkenes) with lower molecular weights (see below).
Lubricating oils(bp 340-400°C) contain hydrocarbons C18 - C25.
Petroleum paraffin(bp. 320-500 ° C), it contains hydrocarbons
C26-C38, from which vaseline is isolated. The residue after distillation is usually called
asphalt or tar.
In addition to hydrocarbons of various classes, oil contains oxygen,
sulfur and nitrogen-containing substances; sometimes their total content reaches
up to several percent.
Currently, the most recognized is the theory of organic
the origin of oil as a product of the transformation of plants and animals
leftovers. This is confirmed by the fact that residues were found in the oil samples.
porphyrins, steroids of plant and animal origin and the so-called
"chemofossils" - the most diverse fragments contained in plankton.
Although it is generally accepted that oil is the most valuable natural resource
chemical raw materials, so far the main amount of oil and oil products
burns in internal combustion engines (gasoline), diesel engines and jet engines
engines (kerosene).
motor fuel. Octane number. Gasolines of various origins
behave differently in internal combustion engines.
In an effort to maximize engine power with small dimensions and
mass, they try to increase the compression ratio of the combustible mixture in the cylinder. However, in
high-speed four-stroke engines working with forced ignition,
in this case, premature ignition of the mixture sometimes occurs -
detonation. This reduces the power of the motor and accelerates its wear. This phenomenon
associated with the composition of liquid fuel, since hydrocarbons of different structures at
when used as a motor fuel, they behave differently. Worst
indicators - for paraffins of normal structure.
The standard for a combustible substance with a high detonation ability is taken
normal heptane. The more branched the carbon chain of the paraffin
hydrocarbon, the better its combustion in the cylinder proceeds and the greater the degree
compression of the combustible mixture can be achieved. As motor fuel standard
adopted 2, 2, 4-trimethylpentane (commonly referred to as isooctane) with good
antiknock properties. Composing in various proportions mixtures of this
octane with n-heptap, compare their behavior in the motor with the behavior of the subject
investigated gasoline, then they say that the latter has octane number 70
assumed to be zero).
One of the ways to improve the knock resistance of fuels for engines with
spark ignition is the application antiknock agents.
Antiknock agents are substances that are added to gasoline (not more than 0.5%) to
improvement of antidetopathic properties. Sufficiently effective antiknock
is an tetraethyl lead(TES) Pb (C2H5)4
However, gasoline from thermal power plants and its combustion products are very toxic. Currently
new antiknock agents based on manganese-organic compounds of the type
cyclopC5H5Mn (CO)5: they are less toxic and
have the best anti-knock properties. Adding these
antiknock to good grades of gasoline allows you to get fuel with
octane up to 135.
For rocket and diesel engines, on the contrary, fuels with
a normal chain of carbon atoms, having the lowest temperature
ignition. This characteristic is taken
evaluate in cetane numbers. A cetane number of 100 has a hydrocarbon
n-Sc, Hd4, and the cetap number 0 is 1-methylnaphthalene.
Synthesis of hydrocarbons from CO+H2. Flowing over finely crushed nickel
a mixture of carbon monoxide (II) and hydrogen at 250 ° C, you can get methane:
CO+3H2CH4+H2O
If this reaction is carried out at a pressure of 100-200 atm and a temperature up to 400°C,
a mixture is obtained, consisting mainly of oxygen-containing products,
among which alcohols predominate; this mixture was called schshpolom.
When using iron-cobalt catalysts and a temperature of 200 ° C,
mixture of alkanes syntin.
nCO + (2n + 1) H2 CnH2n + 2 + H2O
Sintin and synthol are products of large-scale organic synthesis and
are widely used as raw materials for many chemical industries.
Clathrates. Sintin and gasoline fractions of oil are composed of mixtures of hydrocarbons
normal structure and branched chains. Recently found effective
a method for separating organic compounds with normal chains and branched ones,
generally known as clathrate separation method. For
separation of hydrocarbons was used urea. Urea crystals
built in such a way that inside the crystals there are narrow hexagonal
channels. The diameter of these channels is such that it can pass through and linger inside them.
due to adsorption forces, only hydrocarbons of a normal structure. Therefore, when
treatment of a mixture of organic compounds with urea (or some other
compounds) substances with a normal chain of carbon atoms crystallize
together with it in the form of complexes. This method has, of course, a very large
the future is when more effective clathrate formers are found.
Isolation of hydrocarbons from natural raw materials
The sources of saturated hydrocarbons are oil and natural gas.
The main component of natural gas is the simplest hydrocarbon, methane, which is used directly or processed. Oil extracted from the bowels of the earth is also subjected to processing, rectification, and cracking.
Most hydrocarbons are obtained from the processing of oil and other natural resources. But a significant amount of valuable hydrocarbons is obtained artificially, by synthetic methods.
Availability isomerization catalysts accelerates the formation of hydrocarbons with a branched skeleton from linear hydrocarbons:
The addition of catalysts makes it possible to somewhat reduce the temperature at which the reaction proceeds.
Hydrogenation (hydrogen addition) of alkenes
As a result cracking a large number of unsaturated hydrocarbons with a double bond are formed - alkenes. You can reduce their number by adding to the system hydrogen and hydrogenation catalysts- metals (platinum, palladium, nickel):
Cracking in the presence of hydrogenation catalysts with the addition of hydrogen is called reduction cracking. Its main products are saturated hydrocarbons.
Thus, cracking pressure increase(high pressure cracking) allows you to reduce the amount of gaseous (CH 4 - C 4 H 10) hydrocarbons and increase the content of liquid hydrocarbons with a chain length of 6-10 carbon atoms, which form the basis of gasolines.
These were industrial methods for obtaining alkanes, which are the basis for the industrial processing of the main hydrocarbon raw material - oil.
Now consider several laboratory methods for obtaining alkanes.
Heating the sodium salt of acetic acid (sodium acetate) with an excess of alkali leads to elimination of the carboxyl group and the formation of methane:
If instead of sodium acetate we take sodium propionate, then ethane is formed, from sodium butanoate - propane, etc.
At reaction of haloalkanes with alkali metal sodium saturated hydrocarbons and an alkali metal halide are formed, for example:
The action of an alkali metal on a mixture of halocarbons(eg bromoethane and bromomethane) will result in a mixture of alkanes (ethane, propane and butane).
The reaction on which the Wurtz synthesis is based proceeds well only with halogen-alkanes, in the molecules of which a halogen atom is attached to a primary carbon atom.
When processing some carbides containing carbon in the oxidation state -4 (for example, aluminum carbide), water forms methane:
The main methods for obtaining oxygen-containing compounds
The formation of halokenalkanes during the interaction of alcohols with hydrogen halides is a reversible reaction. Therefore, it is clear that alcohols can be obtained by hydrolysis of haloalkanes- reactions of these compounds with water:
Polyhydric alcohols can be obtained by hydrolysis of haloalkanes containing more than one halogen atom in the molecule. For example:
Attachment of water at the π-bond of an alkene molecule, for example:
Leads in accordance with Markovnikov's rule to the formation of secondary alcohol - propanol-2:
Hydrogenation of aldehydes and ketones
Alcohol oxidation under mild conditions leads to the formation of aldehydes or ketones. Obviously, alcohols can be obtained by hydrogenation (hydrogen reduction, hydrogen addition) of aldehydes and ketones:
Glycols, as already noted, can be obtained by oxidation of alkenes with an aqueous solution of potassium permanganate. For example, ethylene glycol (ethane-diol-1,2) is formed during the oxidation of ethylene (ethene):
Specific methods for obtaining alcohols
1. Some alcohols are obtained in ways characteristic only of them. So, methanol in industry is obtained the reaction of interaction of hydrogen with carbon monoxide (II)(carbon monoxide) at elevated pressure and high temperature on the surface of the catalyst (zinc oxide):
The mixture of carbon monoxide and hydrogen necessary for this reaction, also called "synthesis gas", is obtained by passing water vapor over hot coal:
2. Glucose fermentation. This method of obtaining ethyl (wine) alcohol has been known to man since ancient times:
Methods for obtaining aldehydes and ketones
1. Aldehydes and ketones can be obtained by oxidation or dehydrogenation of alcohols. At oxidation or dehydrogenation of primary alcohols aldehydes can be obtained, and secondary alcohols- ketones:
2. . From acetylene, as a result of the reaction, acetaldehyde is obtained, from acetylene homologs - ketones:
3. When heated calcium or barium salts of carboxylic acids a ketone and a metal carbonate are formed:
Methods for obtaining carboxylic acids
1. Carboxylic acids can be obtained oxidation of primary alcohols or aldehydes:
2. Aromatic carboxylic acids are formed during the oxidation of benzene homologues:
3. Hydrolysis of various derivatives of carboxylic acids also produces acids. So, during the hydrolysis of an ester, an alcohol and a carboxylic acid are formed. Acid-catalyzed esterification and hydrolysis reactions are reversible:
4. Hydrolysis of an ester under the action of an aqueous solution of alkali proceeds irreversibly, in this case, not an acid is formed from the ester, but its salt:
Reference material for passing the test:
periodic table
Solubility table
The work was added to the site site: 2015-07-10Order writing a unique work
A17. The main methods for obtaining hydrocarbons (in the laboratory). The main methods for obtaining oxygen-containing compounds (in the laboratory).
"> Obtaining alkanes
Industrial Ways:
- Allocate from natural sources (natural and associated gases, oil, coal).
- "> Hydrogenation of alkenes and unsaturated hydrocarbons.
;text-decoration:underline">Laboratory methods for producing methane:
- ">Thermocatalytic reduction of carbon oxides(t," xml:lang="en-US" lang="en-US">Ni">):
CO + 3H 2 → CH 4 + H 2 O
CO 2 + 4H 2 → CH 4 + 2H 2 O
- "> Synthesis from simple substances: C + 2H;vertical-align:sub">2 ">→ CH ;vertical-align:sub">4
- ">Hydrolysis of aluminum carbide:" xml:lang="en-US" lang="en-US">Al;vertical-align:sub">4 " xml:lang="en-US" lang="en-US">C;vertical-align:sub">3"> + 12 " xml:lang="en-US" lang="en-US">H;vertical-align:sub">2 " xml:lang="en-US" lang="en-US">O"> → 4 " xml:lang="en-US" lang="en-US">Al">(" xml:lang="en-US" lang="en-US">OH">) ;vertical-align:sub">3 "> + 3 " xml:lang="en-US" lang="en-US">CH;vertical-align:sub">4
;text-decoration:underline">Laboratory methods for obtaining methane homologues:
- "> Decarboxylation of sodium salts of carboxylic acids (Dumas reaction). The resulting alkane contains one carbon atom less than the original salt.
" xml:lang="en-US" lang="en-US">CH;vertical-align:sub" xml:lang="en-US" lang="en-US">3" xml:lang="en-US" lang="en-US">COONa + NaOH → CH;vertical-align:sub" xml:lang="en-US" lang="en-US">4" xml:lang="en-US" lang="en-US"> + Na;vertical-align:sub" xml:lang="en-US" lang="en-US">2" xml:lang="en-US" lang="en-US">CO;vertical-align:sub" xml:lang="en-US" lang="en-US">3" xml:lang="en-US" lang="en-US">
- "> Wurtz Synthesis (chain doubling); carried out in order to obtain alkanes with a longer carbon chain.
">2 " xml:lang="en-US" lang="en-US">CH;vertical-align:sub">3 " xml:lang="en-US" lang="en-US">Cl"> + 2 " xml:lang="en-US" lang="en-US">Na"> → " xml:lang="en-US" lang="en-US">C;vertical-align:sub">2 " xml:lang="en-US" lang="en-US">H;vertical-align:sub">6"> + 2 " xml:lang="en-US" lang="en-US">NaCl">
- Electrolysis of sodium acetate:
electrolysis
2 CH 3 COONa + 2H 2 O → C2 H6 + 2CO2 + H2 + 2 NaOH
Obtaining alkenes
In the laboratory:
1. Dehydrohalogenation of haloalkanes is carried out with an alcohol solution of alkali:
CH 3 - CH 2 Cl + KOH (alcohol) → CH 2 = CH 2 + KCl + H 2 O
CH 3 - CH - CH 2 - CH 3 + KOH (alcohol) → CH 3 - CH \u003d CH - CH 3 + KI + H 2 O
Rule A.M. Zaitsev: "Hydrogen is split off from a less hydrogenated carbon atom."
2. Dehydration of alcohols proceeds in the presence of concentrated sulfuric acid or anhydrous aluminum oxide when heated (t> 150o C) with the formation of alkenes.
CH 3 - CH 2 - CH 2 OH → CH 3 - CH \u003d CH 2 + H 2 O
3. Dehalogenation of dihalogen derivatives is carried out using finely divided zinc or magnesium:
CH 3 - CH - CH 2 + Zn → CH 3 - CH \u003d CH 2 + ZnCl 2
Cl Cl
In industry:
1, The main way to obtain alkenes is the cracking of alkanes, leading to the formation of a mixture of low molecular weight alkenes and alkanes, which can be separated by distillation.
C5 H12 → C2 H4 + C3 H8 (or C3 H6 + C2 H6), etc.
2 Dehydrogenation of alkanes. (catalysts: Pt ; Ni ; AI 2 O 3 ; Cr 2 O 3 )
Ni, 450 – 5000 C
CH3 - CH3 → CH2 = CH2 + H2
550 - 6500 C
2CH 4 → CH 2 = CH2 + 2H2
3. Catalytic hydrogenation of alkynes (catalysts: Pt ; Ni ; Pd )
CH ≡ CH + H2 → CH2 = CH2
Obtaining cycloalkanes
- The action of the active metal on the dihaloalkane:
t, p, Ni
Br - C H2 -C H2 -C H2 -Br + Mg → + Mg Br 2
1,3-dibromopropane
- Hydrogenation of arenes (t, p, Pt)
C6 H6 + 3 H2 →
Obtaining alkynes
Acetylene:
a) methane method:
2CH4 C2 H2 + 3H2
b) hydrolysis of calcium carbide (laboratory method):
CaC 2 + 2H 2 O C 2 H 2 + Ca (OH) 2
CaO + 3C CaC 2 + CO
Due to the high energy consumption, this method is economically less profitable.
Synthesis of acetylene homologues:
a) catalytic dehydrogenation of alkanes and alkenes:
Сn H 2 n +2 C n H 2 n -2 + 2H 2
Сn H 2 n C n H 2 n -2 + H 2
b) dehydrohalogenation of dihaloalkanes with an alcohol solution of alkali (alkali and alcohol are taken in excess):
Cn H 2 n G2 + 2KOH (sp) C n H 2 n -2 + 2K G + 2H 2 O
Obtaining alkadienes
- Dehydrogenation of alkanes contained in natural gas and refinery gases by passing them over a heated catalyst
t, Cr 2 O 3 , Al 2 O 3
CH 3 -CH 2 -CH 2 -CH 3 → CH 2 \u003d CH-CH \u003d CH 2 + 2H 2
t, Cr 2 O 3 , Al 2 O 3
CH 3 -CH-CH 2 -CH 3 → CH 2 \u003d C-CH \u003d CH 2 + 2H 2
CH 3 CH 3
- Dehydrogenation and dehydration of ethyl alcohol by passing alcohol vapor over heated catalysts (method of academician S.V. Lebedev):
t, ZnO, Al 2 O 3
2CH 3 CH 2 OH → CH 2 \u003d CH–CH \u003d CH 2 + 2H 2 O + H 2
Getting arenas
Benzene
- Trimerization of alkynes over activated carbon (Zelinsky):
Act. C, 600 C
3HCCH C6 H 6 (benzene)
- In the laboratory by fusing salts of benzoic acid with alkalis:
C6 H5 - COOHa + Na OH → C6 H6 + Na 2 CO3
Benzene and homologues
- During the coking of coal, coal tar is formed, from which benzene, toluene, xylenes, naphthalene and many other organic compounds are isolated.
- Dehydrocyclization (dehydrogenation and cyclization) of alkanes in the presence of a catalyst:
Cr2O3
CH 3 -CH 2 -CH 2 -CH 2 -CH 2 -CH 3 C 6 H 6 + 4H 2
Hexane produces benzene, and heptane produces toluene.
- Dehydrogenation of cycloalkanes
→ C6 H6 + 3 H2
- Obtaining homologues - alkylation of benzene with haloalkanes or alkenes in the presence of anhydrous aluminum chloride:
AlCl 3
C 6 H 6 + C 2 H 5 Cl C 6 H 5 C 2 H 5 + HCl
chloroethane ethylbenzene
Obtaining saturated monohydric alcohols
General methods
- Hydration of alkenes (according to Markovnikov's rule):
t, H 2 SO 4
CH3 -CH \u003d CH2 + H-OH → CH3 -CH-CH3
OH (propanol-2)
- Hydrolysis of haloalkanes under the action of an aqueous solution of alkali:
C 2 H 5 I + Na OH (aq.) → C 2 H 5 -O H + NaI
- Recovery (hydrogenation) of aldehydes and ketones.
Hydrogenation of aldehydes produces primary alcohols:
t, Ni
CH3 -CH2 -CHO + H2 → CH3 -CH2 - CH2 -OH
propanol-1
When ketones are hydrogenated, secondary alcohols are formed:
t, Ni
CH3 -C-CH3 + H2 → CH3 -CH-CH3
O OH (propanol-2)
Specific methods of obtaining
- Methanol - from synthesis gas:
t, p, cat
CO + 2H2 → CH3 OH
- Ethanol - alcoholic fermentation of glucose (enzymatic):
C6 H12 O6 → 2C2 H5 OH + 2CO2
ethylene glycol
- In the laboratory - the Wagner reaction.
Oxidation of ethylene with potassium permanganate in a neutral medium leads to the formation of dihydric alcohol - ethylene glycol.
Simplified:
KMnO 4 , H 2 O
CH 2 \u003d CH 2 + HOH + → CH 2 - CH 2
OH OH
3 CH 2 \u003d CH 2 + 2KMnO 4 + 4H 2 O → 3 CH 2 - CH 2 + 2MnO 2 + 2KOH
OH OH
- In industry - hydrolysis of 1,2-dichloroethane:
CH2 Cl - CH2 Cl + 2NaOH → CH2 (OH)-CH2 OH + 2NaCl
Glycerol
- Fat hydrolysis:
- From propene:
a) CH2 = CH-CH3 + Cl 2 → CH2 = CH-CH2 Cl
3-chloropropene-1
b) CH2 \u003d CH-CH2 Cl + NaOH (aq.) → CH2 \u003d CH-CH2 -OH + N aCl
allyl alcohol
c) CH2 = CH-CH2 -OH + H2 O2 → CH2 -CH-CH2
Obtaining phenols
- Extraction from coal tar.
- Hydrolysis of chlorobenzene:
C6 H5 -Cl + H2 O (steam) → C6 H5 -OH + HCl
- Oxidation of isopropylbenzene (cumene) with atmospheric oxygen:
Getting ethers
- Intermolecular dehydration of ethanol:
t, H2SO4
2C2 H5 OH → C2 H5 -O-C2 H5 + H2 O
- The interaction of a metal alcoholate with halogen derivatives of alkanes:
C 2 H 5 I + C 2 H 5 ONa → C 2 H 5 -O-C 2 H 5 + NaI
Obtaining aldehydes
General way
- Alcohol oxidation. Primary alcohols are oxidized to aldehydes, and secondary alcohols to ketones:
t, Cu
2C 2 H 5 OH + O 2 → 2CH 3 CHO + 2H 2 O
T , Cu
CH3 -CH-CH3 + O 2 → CH3 -C-CH3
OH (propanol-2) O
Specific ways
- Formaldehyde is produced by the catalytic oxidation of methane:
CH 4 + O 2 → HC HO + H 2 O
- Acetic aldehyde (acetaldehyde):
a) Kucherov reaction
H+, Hg 2+
HCCH + H2 O CH3 -CHO
b) catalytic oxidation of ethylene
2CH2 \u003d CH2 + O2 → 2CH3 -CHO
Obtaining carboxylic acids
General methods
- Oxidation of aldehydes under the action of various oxidizing agents:
R-CHO + Ag 2 O (amm.) → R-C OOH + 2Ag ↓
" xml:lang="en-US" lang="en-US"> t
R-CHO + 2Cu(OH) 2 →R-COOH + Cu 2 O↓ + 2H 2 O
- "> Catalytic oxidation - methane homologues are oxidized with a break in the C-C chain and the formation of carboxylic acids:
"> 2 " xml:lang="en-US" lang="en-US">C;vertical-align:sub">4 " xml:lang="en-US" lang="en-US">H;vertical-align:sub">10">+ 5 " xml:lang="en-US" lang="en-US">O;vertical-align:sub">2"> → 4CH ;vertical-align:sub">3 " xml:lang="en-US" lang="en-US">COO">H+ 2 " xml:lang="en-US" lang="en-US">H;vertical-align:sub">2 " xml:lang="en-US" lang="en-US">O">
Specific ways
- Formic acid is obtained by heating under pressure powdered sodium hydroxide and carbon monoxide, followed by treatment of the resulting sodium formate with a strong acid:
NaOH + CO → HCOONa
H 2 SO 4 + 2HCOONa → HCOO H + Na 2 SO 4
- Acetic acid:
a) For food purposes, they are obtained by enzymatic fermentation (oxidation) of liquids containing alcohol (wine, beer):
enzymes
C 2 H 5 OH + O2 → CH 3 C OOH + H 2 O
b) In the laboratory from acetates:
2CH3 COONa + H 2 SO 4 → 2CH3 COO H + Na 2 SO 4
Obtaining esters
- Esterification reaction when an acid and an alcohol are heated in the presence of sulfuric acid or other mineral acids. Isotopic studies have shown that in the esterification reaction, a hydrogen atom is separated from an alcohol molecule, and a hydroxyl group is separated from an acid molecule.
This reaction is reversible and obeys Le Chatelier's rule. To increase output
esters, it is necessary to remove the resulting water from the reaction medium.
CH3 -COOH + HOCH2 CH3 → CH3-CO-O-CH2 CH3 + H2 O
Getting soap
- "> Alkaline hydrolysis (saponification of fats occurs irreversibly under the action of alkalis):
- "> Neutralization of carboxylic acids obtained by catalytic oxidation of higher oil paraffins:
">2 C ;vertical-align:sub">32 ">H ;vertical-align:sub">66 "> + 5O ;vertical-align:sub">2 ">→ 4C ;vertical-align:sub" >15 ">H ;vertical-align:sub">31">COOH + 2H ;vertical-align:sub">2">O
"> palmitic acid
"> C ;vertical-align:sub">15 ">H ;vertical-align:sub">31 ">COOH + " xml:lang="en-US" lang="en-US">NaOH"> → C ;vertical-align:sub">15 ">H ;vertical-align:sub">31 ">COO " xml:lang="en-US" lang="en-US">Na">">+ N ;vertical-align:sub">2 " xml:lang="en-US" lang="en-US">O">
"> sodium palmitate (solid soap)
"> C ;vertical-align:sub">15 ">H ;vertical-align:sub">31 ">COOH + K " xml:lang="en-US" lang="en-US">OH"> → C ;vertical-align:sub">15 ">H ;vertical-align:sub">31 ">COO ">K ">+ H ;vertical-align:sub">2 " xml:lang="en-US" lang="en-US">O">
"> potassium palmitate (liquid soap)
Getting carbohydrates
- Glucose - by hydrolysis of starch or cellulose:
(C6 H10 O5 )n + nH2 O nC6 H12 O6
- Sucrose - from sugar beet and sugar cane.
